JP7315927B2 - Semiconductor device and its manufacturing method - Google Patents

Description

The technology disclosed in this specification relates to a semiconductor device and a manufacturing method thereof.

Patent Document 1 discloses a semiconductor device having a structure in which an ε-type (AlGa) ₂ O ₃ layer is laminated on an ε-type Ga ₂ O ₃ layer.

JP 2019-009405 A

A technique for suitably growing a cubic system semiconductor has not been established. Therefore, this specification proposes a technique for suitably growing a cubic system semiconductor.

A method for manufacturing a semiconductor device disclosed in the present specification is a method for forming a different layer from the first layer on a first layer composed of Ga _2-x Fe _x O ₃ (0<x<2) by a mist CVD method. growing a second layer composed of a semiconductor material having a composition and having a cubic crystal structure.

The mist CVD method is a CVD method (chemical vapor deposition) in which mist is reacted to grow a film.

According to this manufacturing method, the second layer having a cubic crystal structure can be suitably grown on the first layer composed of Ga _2-x Fe _x O ₃ .

FIG. 2 is an explanatory diagram of the film forming apparatus 10; FIG. 4 is a cross-sectional view of a substrate 70 and a gallium oxide film 72; FIG. 4 is a diagram showing the result of X-ray analysis of the substrate 70 and the gallium oxide film 72 by 2θ scanning; FIG. 4 is a diagram showing the results of X-ray analysis of the gallium oxide film 72 by φ scanning; FIG. 10 is a diagram showing the result of X-ray analysis of a gallium oxide film of a comparative example by φ scanning; FIG. 4 is a diagram showing the surface of a substrate 70 (ε-GaFeO ₃ ); FIG. 4 shows the surface of a gallium oxide film 72 (κ-Ga ₂ O ₃ ); Explanatory drawing of the film-forming apparatus 100. FIG. FIG. 3 is a cross-sectional view of a substrate 70, a gallium oxide film 72, and an aluminum gallium oxide film 74; FIG. 10 is a cross-sectional view of an example of a semiconductor device manufactured by the manufacturing method of Embodiment 2; FIG. 4 is a cross-sectional view of a substrate 70 and an indium gallium oxide film 76; FIG. 3 is a cross-sectional view of a substrate 70, an indium gallium oxide film 76, and a gallium oxide film 78; FIG. 11 is a cross-sectional view of an example of a semiconductor device manufactured by the manufacturing method of Example 3;

The features of the technology disclosed in this specification are listed below. It should be noted that the following features are useful independently and can also be used in combination.

The first layer may be composed of ε-Ga _2-x Fe _x O ₃ . According to this configuration, a higher quality second layer can be grown.

The first layer may be composed of Ga _2-x Fe _x O ₃ (0.7≦x≦1.5). In this case, the first layer may be composed of GaFeO ₃ . According to these configurations, a second layer of higher quality can be grown.

The second layer may be free of domains of rotation within at least a 1 μm×1 μm square. Rotation domains are likely to occur in the second layer of the cubic system, but the production method disclosed in the present specification can suppress the occurrence of rotation domains.

The second layer may be composed of In _a Al _{b Gac} O ₃ (0≦a≦2, 0≦b≦2, 0≦c≦2, 1.5≦a+b+c≦2.5) .

_The second layer _may be composed _of κ- _InaAlbGacO3 . If both the first layer and the second layer are κ-type, the lattice matching at the interface between them can be further improved.

The second layer may be composed of In _{a Gac} O ₃ (0≦a≦2, 0≦c≦2, 1.9≦a+c≦2.1). In _{a Gac} O ₃ is particularly easy to match with the first layer (Ga _2-x Fe _x O ₃ ).

The second layer may be heteroepitaxially grown on the first layer.

A third layer of semiconductor material having a composition different from that of the first layer may be grown on the second layer.

The third layer may have a cubic crystal structure.

The third layer may be free of domains of rotation within at least a 1 μm×1 μm square.

The third layer may be composed of _InuAlvGawO3 (0≤u≤2, 0≤v≤2 _, 0≤w≤2, 1.5≤u+v _{+ w≤2.5} ) .

_The third layer may be composed _of κ- _{InuAlvGawO3 .} If both the second layer and the third layer are of κ type, the lattice matching at the interface therebetween can be further improved.

When _{the second layer is composed of InaAlbGacO3 and the third layer is composed of InuAlvGawO3 , a > u may be satisfied} . Alternatively, b<v. According to these configurations, the bandgap of the third layer can be made larger than the bandgap of the second layer. In the HEMT, the third layer can be used as an electron supply layer, and the second layer can be used as an electron transit layer.

The third layer may be made of Al _v Ga _w O ₃ (0≦v≦2, 0≦w≦2, 1.9≦u+v+w≦2.1). With this configuration, the third layer can be used as an electron supply layer. Also, a high-quality third layer can be formed more stably.

The third layer may be formed by a mist CVD method.

The third layer may be heteroepitaxially grown on the second layer.

FIG. 1 shows a film forming apparatus 10 used in the manufacturing method of Example 1. As shown in FIG. The film forming apparatus 10 is an apparatus for forming an oxide film on a substrate 70 by mist CVD. The film forming apparatus 10 includes a furnace 12 in which a substrate 70 is placed, a heater 14 for heating the furnace 12, a mist supply device 20 connected to the furnace 12, and a discharge pipe 80 connected to the furnace 12. .

A specific configuration of the furnace 12 is not particularly limited. By way of example only, the furnace 12 shown in FIG. 1 is a tubular furnace extending from an upstream end 12a to a downstream end 12b. A cross section perpendicular to the longitudinal direction of the furnace 12 is circular. For example, furnace 12 may have a diameter of about 40 mm. However, the cross section of the furnace 12 is not limited to a circular shape.

A mist supply device 20 is connected to the upstream end 12 a of the furnace 12 . A discharge pipe 80 is connected to the downstream end 12 b of the furnace 12 . The mist supply device 20 supplies mist 62 into the furnace 12 . The mist 62 supplied into the furnace 12 by the mist supply device 20 is discharged to the outside of the furnace 12 through the discharge pipe 80 after flowing through the furnace 12 to the downstream end 12b.

A substrate stage 13 for supporting the substrate 70 is provided in the furnace 12 . The substrate stage 13 is configured such that the substrate 70 is tilted with respect to the longitudinal direction of the furnace 12 . The substrate 70 supported by the substrate stage 13 is supported in such a direction that mist flowing in the furnace 12 from the upstream end 12 a toward the downstream end 12 b hits the surface of the substrate 70 .

Heater 14 heats furnace 12 as previously described. A specific configuration of the heater 14 is not particularly limited. As an example, the heater 14 shown in FIG. 1 is an electric heater and is arranged along the outer peripheral wall of the furnace 12 . As a result, the heater 14 heats the outer peripheral wall of the furnace 12 , thereby heating the substrate 70 inside the furnace 12 .

The mist supply device 20 has a mist generator 22 . The mist generator 22 has a water tank 24 , a solution storage tank 26 and an ultrasonic oscillator 28 . The water tank 24 is a container with an open top, and stores water 58 inside. The ultrasonic transducer 28 is installed on the bottom surface of the water tank 24 . The ultrasonic vibrator 28 applies ultrasonic vibrations to the water 58 in the water tank 24 . The solution storage tank 26 is a closed container. The solution storage tank 26 stores a solution 60 containing raw materials for a film to be epitaxially grown on the surface of the substrate 70 . In addition, raw materials (for example, ammonium fluoride, etc.) for imparting an n-type or p-type dopant to the film to be grown may be further dissolved in the solution 60 . The bottom of solution reservoir 26 is immersed in water 58 in water tank 24 . The bottom surface of the solution storage tank 26 is made of a film. This makes it easier for ultrasonic vibrations to be transmitted from the water 58 in the water tank 24 to the solution 60 in the solution storage tank 26 . When the ultrasonic vibrator 28 applies ultrasonic vibrations to the water 58 in the water tank 24 , the ultrasonic vibrations are transmitted to the solution 60 through the water 58 . Then, the surface of the solution 60 vibrates, and a mist 62 of the solution 60 is generated in the space above the solution 60 (that is, the space inside the solution storage tank 26).

The mist supply device 20 further includes a mist supply path 40 , a carrier gas supply path 42 and a dilution gas supply path 44 . A mist supply path 40 connects between the solution storage tank 26 and the furnace 12 . A carrier gas supply path 42 is connected to the solution storage tank 26 . The dilution gas supply path 44 is connected to the mist supply path 40 . A carrier gas supply line 42 supplies a carrier gas 64 to the solution storage tank 26 . The dilution gas supply path 44 supplies the dilution gas 66 to the mist supply path 40 .

Next, the manufacturing method of Example 1 will be described. In the manufacturing method of Example 1, a substrate made of a single crystal of ε-type gallium iron oxide (ε-GaFeO ₃ ) is used as the substrate 70 . As the solution 60, an aqueous solution (gallium chloride aqueous solution) in which gallium chloride (GaCl ₃ or Ga ₂ Cl ₆ ) is dissolved in water is used. Nitrogen gas (N ₂ ) is used as the carrier gas 64 and nitrogen gas is used as the diluent gas 66 .

As shown in FIG. 1, first, a substrate 70 is placed on the substrate stage 13 inside the furnace 12 . Next, the substrate 70 is heated by the heater 14 . Here, the temperature of the substrate 70 is controlled to approximately 750.degree. After the temperature of the substrate 70 is stabilized, the mist supply device 20 is activated. That is, by operating the ultrasonic oscillator 28, a mist 62 of the solution 60 is generated in the solution storage tank 26. FIG. At the same time, a carrier gas 64 is introduced from the carrier gas supply path 42 into the solution storage tank 26 and a dilution gas 66 is introduced from the dilution gas supply path 44 into the mist supply path 40 . Carrier gas 64 flows through solution reservoir 26 and into mist supply channel 40 as indicated by arrow 47 . At this time, the mist 62 in the solution storage tank 26 flows into the mist supply path 40 together with the carrier gas 64 . Also, the diluent gas 66 is mixed with the mist 62 in the mist supply passage 40 . The mist 62 is thereby diluted. Mist 62 flows downstream through mist supply passage 40 along with nitrogen gas (ie, carrier gas 64 and diluent gas 66 ) and enters furnace 12 through mist supply passage 40 as indicated by arrow 48 . Inside the furnace 12 , the mist 62 flows to the downstream end 12 b side together with the nitrogen gas and is discharged to the discharge pipe 80 .

A portion of the mist 62 flowing through the furnace 12 adheres to the surface of the heated substrate 70 . The mist 62 (that is, the solution 60 ) then undergoes chemical reactions on the substrate 70 . As a result, gallium oxide grows on the substrate 70 . Since the substrate 70 is composed of ε-GaFeO ₃ of a cubic system, κ-type gallium oxide (κ-Ga ₂ O ₃ ) of a cubic system grows on the substrate 70 . Since the mist 62 is continuously supplied to the surface of the substrate 70, a gallium oxide film 72 composed of κ-Ga ₂ O ₃ grows on the surface of the substrate 70 as shown in FIG.

FIG. 3 shows the results of X-ray analysis of the substrate 70 and the gallium oxide film 72 by 2θ scanning. As shown in FIG. 3, only the peak of the substrate 70 (ε-GaFeO ₃ ) and the peak of κ-Ga ₂ O ₃ were detected from the gallium oxide film 72 . From this result, it was confirmed that the gallium oxide film 72 was composed of κ-Ga ₂ O ₃ .

FIG. 4 shows the result of X-ray analysis of the gallium oxide film 72 by φ scanning. Further, FIG. 5 shows the result of X-ray analysis of the gallium oxide film of the comparative example by φ scanning. A gallium oxide film of a comparative example was formed on a gallium nitride substrate (GaN) by a mist CVD method. The gallium oxide film of the comparative example is composed of κ-Ga ₂ O ₃ . As shown in FIG. 4, four peaks were detected in the gallium oxide film 72 formed by the manufacturing method of Example 1. FIG. This confirms that the gallium oxide film 72 is a single crystal. On the other hand, as shown in FIG. 5, 12 peaks were detected in the gallium oxide film of the comparative example. This means that the gallium oxide film of the comparative example has domains of rotation in three directions. Conventionally, when κ-Ga ₂ O ₃ is formed, ε-Ga ₂ O ₃ (hexagonal system) is mixed in some cases. As described above, conventionally, it has been difficult to form a single crystal film of κ-Ga ₂ O ₃ having a rectangular system. On the other hand, as described above, according to the manufacturing method of Example 1, a single crystal film of κ-Ga ₂ O ₃ can be formed.

Also, FIG. 6 shows the surface of the substrate 70 (ε-GaFeO ₃ ) before forming the gallium oxide film 72 . Also, FIG. 7 shows the surface of the gallium oxide film 72 (κ-Ga ₂ O ₃ ). The RMS (root mean square roughness) of the surface of the substrate 70 shown in FIG. 6 was 0.14 nm. The RMS of the surface of the gallium oxide film 72 shown in FIG. 7 was 0.15 nm. Thus, it was confirmed that the gallium oxide film 72 was grown while maintaining its flatness.

A semiconductor device can be manufactured using the gallium oxide film 72 formed as described above. For example, another film may be heteroepitaxially grown on the gallium oxide film 72 to manufacture a semiconductor device. By manufacturing a semiconductor device using the gallium oxide film 72 composed of a single crystal of κ-Ga ₂ O ₃ in this way, a semiconductor device (for example, a power device, a high-frequency device, etc.) having characteristics different from conventional ones can be obtained. ) can be obtained.

FIG. 8 shows a film forming apparatus 100 used in the manufacturing method of Example 2. As shown in FIG. The film forming apparatus 100 differs from the film forming apparatus 10 in FIG. 1 in the configuration of the mist supply device 20, and the rest of the configuration (the furnace 12, the heater 14, the exhaust pipe 80, etc.) is the same as the film forming apparatus in FIG. The mist supply device 20 of FIG. 8 has a mist generator 22, a mist supply path 40, a carrier gas supply path 42, and a diluent gas supply path 44, similarly to the mist supply apparatus 20 of FIG. 8 further includes a mist generator 122, a mist supply path 140, a carrier gas supply path 142, a diluent gas supply path 144, and a switching valve 150. FIG. The mist generator 122 operates similarly to the mist generator 22 . That is, by operating the ultrasonic vibrator 128 , ultrasonic vibrations are transmitted to the solution storage tank 126 via the water 158 in the water tank 124 , and mist 162 of the solution 160 is generated in the solution storage tank 126 . Mist 162 flows into mist supply channel 140 along with carrier gas 164 . The mist 162 is diluted by the dilution gas 166 within the mist supply path 140 . The mist 162 flows downstream through the mist supply path 140 . The mist supply path 140 and the mist supply path 40 merge at the downstream portion. The switching valve 150 opens and closes the mist supply path 40 and the mist supply path 140 . The switching valve 150 switches between a state in which the mist 62 flows from the mist supply path 40 to the furnace 12 and a state in which the mist 162 flows from the mist supply path 140 to the furnace 12 .

In the manufacturing method of Example 2, a substrate composed of a single crystal of ε-type gallium iron oxide (ε-GaFeO ₃ ) is used as the substrate 70 . Also, as the solution 60, an aqueous solution of gallium acetylacetonate is used. As the solution 160, a mixed solution of an aluminum acetylacetonate aqueous solution and a gallium acetylacetonate aqueous solution is used. Nitrogen gas is used as the carrier gases 64 and 164 and nitrogen gas is used as the diluent gases 66 and 166 .

In the manufacturing method of Example 2, the substrate 70 is placed on the substrate stage 13 in the furnace 12 and the substrate 70 is heated. Next, the switching valve 150 opens the mist supply path 40 and closes the mist supply path 140 . In this state, the mist generator 22 is operated to supply the mist 62 of the solution 60 (gallium acetylacetonate aqueous solution) into the furnace 12 . Then, a gallium oxide film 72 composed of a single crystal of κ-Ga ₂ O ₃ is grown on the substrate 70 in substantially the same manner as in the first embodiment.

Next, the switching valve 150 closes the mist supply path 40 and opens the mist supply path 140 . Further, the mist generator 122 is operated to supply the mist 162 of the solution 160 (mixture of aluminum acetylacetonate aqueous solution and gallium acetylacetonate aqueous solution) into the furnace 12 . Then, the mist 162 (that is, the solution 160) causes a chemical reaction on the gallium oxide film 72. FIG. As a result, on the gallium oxide film 72, κ-type aluminum gallium oxide (κ-Al _v Ga _w O ₃ (0≤v≤2, 0≤w≤2, 1.9≤v+w≤ 2.1)) grow. Since the mist 162 is continuously supplied, an aluminum gallium oxide film 74 composed of a single crystal of κ-Al _v Ga _w O ₃ grows on the surface of the gallium oxide film 72 as shown in FIG. Since both the gallium oxide film 72 and the aluminum gallium oxide film 74 are of the κ type and of the cubic system, a high-quality aluminum gallium oxide film 74 with few crystal defects is formed. In particular, since the surface of the gallium oxide film 72 is flat as shown in FIG. 7, an aluminum gallium oxide film 74 with high crystallinity can be grown thereon. An interface 75 between the gallium oxide film 72 and the aluminum gallium oxide film 74 becomes a high-quality heterointerface with high lattice matching.

Using the gallium oxide film 72 and the aluminum gallium oxide film 74 formed as described above, a semiconductor device (eg, power device, high frequency device, etc.) can be manufactured. Since the interface 75 is a heterointerface with high lattice matching, a two-dimensional electron gas is generated at the interface 75 . Therefore, a semiconductor device using a two-dimensional electron gas may be manufactured. For example, as shown in FIG. 10, a source electrode 90 and a drain electrode 92 are provided so as to be electrically connected to a heterointerface 75, and a gate electrode 94 is provided on an aluminum gallium oxide film 74, thereby forming a high electron mobility transistor (HEMT). high electron mobility transistors) may be fabricated. In another example, a heterojunction bipolar transistor (HBT) may be fabricated.

In the manufacturing method of Example 3, the film forming apparatus 100 of FIG. 8 is used as in the manufacturing method of Example 2. FIG. In the manufacturing method of Example 3, a substrate made of a single crystal of ε-type gallium iron oxide (ε-GaFeO ₃ ) is used as the substrate 70 . As the solution 60, a mixed solution of gallium chloride aqueous solution and indium chloride aqueous solution is used. Further, as the solution 160, an aqueous solution of gallium chloride is used. Nitrogen gas is used as the carrier gases 64 and 164 and nitrogen gas is used as the diluent gases 66 and 166 .

In the manufacturing method of Example 3, the substrate 70 is placed on the substrate stage 13 in the furnace 12 and the substrate 70 is heated. Next, the switching valve 150 opens the mist supply path 40 and closes the mist supply path 140 . In this state, the mist generator 22 is operated to supply the mist 62 of the solution 60 (mixed solution of gallium chloride aqueous solution and indium chloride aqueous solution) into the furnace 12 . The mist 62 (that is, the solution 60 ) then undergoes chemical reactions on the substrate 70 . As a result, κ-type indium gallium oxide (κ-In _{a Gac} O ₃ (0≤a≤2, 0≤c≤2, 1.9≤a+c≤2. 1)) is generated. Since the mist 62 is continuously supplied, an indium gallium oxide film 76 composed of a single crystal of κ-In _{a Gac} O ₃ grows on the surface of the substrate 70 as shown in FIG. Since both the substrate 70 and the indium gallium oxide film 76 are of the cubic system, a high-quality indium gallium oxide film 76 with few crystal defects is formed.

Next, the switching valve 150 closes the mist supply path 40 and opens the mist supply path 140 . Further, the mist generator 122 is operated to supply the mist 162 of the solution 160 (gallium chloride aqueous solution) into the furnace 12 . The mist 162 (ie, the solution 160 ) then undergoes a chemical reaction on the indium gallium oxide film 76 . As a result, κ-type gallium oxide (κ-Ga ₂ O ₃ ) of a cubic system is generated on the indium gallium oxide film 76 . Since the mist 162 is continuously supplied, a gallium oxide film 78 composed of a single crystal of κ-Ga ₂ O ₃ grows on the surface of the indium gallium oxide film 76 as shown in FIG. Since both the indium gallium oxide film 76 and the gallium oxide film 78 are of the κ type and of the cubic system, a high-quality gallium oxide film 78 with few crystal defects is formed. An interface 79 between the indium gallium oxide film 76 and the gallium oxide film 78 becomes a high-quality heterointerface with high lattice matching.

Using the indium gallium oxide film 76 and the gallium oxide film 78 formed as described above, a semiconductor device (eg, power device, high frequency device, etc.) can be manufactured. Since the interface 79 is a heterointerface with high lattice matching, a two-dimensional electron gas is generated at the interface 79 . Therefore, a semiconductor device using a two-dimensional electron gas may be manufactured. For example, as shown in FIG. 13, a HEMT may be manufactured by providing a source electrode 95 and a drain electrode 96 so as to conduct with the heterointerface 79 and providing a gate electrode 97 on the gallium oxide film 78 . In another example, a HBT (heterojunction bipolar transistor) may be fabricated.

In Examples 1 to 3 described above, the substrate 70 was made of ε-GaFeO ₃ . However, the substrate 70 can be composed of Ga _2-x Fe _x O ₃ (0<x<2) and the value of x can be changed accordingly. By changing the value of x, it may be possible to relax the stress generated at the interface between the substrate 70 and the film formed thereon, or improve the adhesion of the film at the interface. Further, in Examples 1 to 3 described above, the substrate 70 is made of Ga _2-x Fe _x O ₃ , but Ga _2-x Fe _x O ₃ may be used for the buffer layer. That is, a layer of Ga _2-x Fe _x O ₃ may be formed as a buffer layer on the surface of a substrate made of another material, and a cubic system semiconductor layer may be grown on the buffer layer. When Ga _2-x Fe _x O ₃ is used as a buffer layer, Ga _2-x Fe _x O ₃ may be stacked in a superlattice shape while changing the value of x.

Although the embodiments have been described in detail above, they are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or in the drawings exhibit technical usefulness either singly or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the techniques exemplified in this specification or drawings simultaneously achieve a plurality of purposes, and achieving one of them has technical utility in itself.

70: substrate 72: gallium oxide film 74: aluminum gallium oxide film 75: hetero interface

Claims (2)

A method for manufacturing a semiconductor device,
A semiconductor material having a composition different from that of the first layer is formed on a first layer made of Ga _2-x Fe _x O ₃ (0<x<2) by a mist CVD method, and a cubic crystal is formed on the first layer. growing a second layer having a crystal structure of the
Production method. A semiconductor device,
a first layer composed of Ga _2-x Fe _x O ₃ (0<x<2);
A second layer disposed on the first layer, made of a semiconductor material having a composition different from that of the first layer, and having a cubic crystal structure;
A semiconductor device having

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