GALLIUM NITRIDE-BASED SINTERED COMPACT AND METHOD FOR MANUFACTURING SAME

Abstract

A sputtering target for a gallium nitride thin film, which has a low oxygen content, a high density and a low resistivity. A gallium nitride powder having powder physical properties of a low oxygen content and a high bulk density is used and hot pressing is conducted at high temperature in high vacuum to prepare a gallium nitride sintered body having a low oxygen content, a high density and a low resistivity.

Claims

1. A gallium nitride-based film having an intensity ratio of (002) plane to (101) plane in 2θ/θ measurement by an X-ray diffraction apparatus, I(002)/I(101) of at least 150 and a minimum oxygen content of at most 5×10.sup.21 atm/cm.sup.3.

2. The gallium nitride-based film according to claim 1 having a half value width of the ω measurement peak of (002) plane of at most 2°.

3. The gallium nitride-based film according to claim 1, having a half value width of the 2θ/θ measurement peak of (002) plane of at most 0.3°.

4. The gallium nitride-based film according to claim 1, having a hexagonal crystal phase.

5. A laminated substrate, comprising: a substrate; and the gallium nitride-based film of claim 1.

6. The laminated substrate according to claim 5, further comprising: a metal sulfide layer, wherein the substrate comprises a silicon single crystal layer, the metal sulfide layer is present between the silicon single crystal layer and the gallium nitride based film, and a surface roughness Ra is at most 10 nm.

7. The laminated substrate according to claim 6, wherein the metal sulfide layer is laminated on the silicon single crystal layer.

8. The laminated substrate according to claim 6, wherein the metal sulfide layer comprises a manganese sulfide layer.

9. The laminated substrate according to claim 6, wherein the silicon single crystal layer comprises a Si(100) substrate.

10. A method for producing the gallium nitride-based film of claim 1, comprising: forming the gallium nitride-based film by sputtering under a sputtering gas pressure of less than 0.3 Pa.

11. The method according to claim 10, further comprising, before the forming: setting a degree of vacuum in a film forming apparatus to be at most 3×10.sup.−5 Pa.

12. The method according to claim 10, wherein the forming includes heating a substrate at a heating temperature of 100° C.-800° C.

13. A semiconductor device, comprising: the laminated substrate of claim 5.

14. An electronic equipment, comprising: the laminated substrate of claim 5.

Description

EXAMPLES

[0078] Now, the present invention will be described with reference to Examples of the present invention, however, it should be understood that the present invention is by no means restricted thereto.

(Specific Surface Area)

[0079] The specific surface area of the powder was measured by Micrometrics Tristar.

(Untamped Bulk Density)

[0080] The untamped bulk density was measured by Powder Characteristics Tester PT-N (manufactured by HOSOKAWA MICRON CORPORATION).

(Bulk Density of Sintered Body)

[0081] The bulk density of the sintered body was measured in accordance with bulk density measurement in JIS R1634.

(Oxygen Content)

[0082] The oxygen content of the sintered body was measured by oxygen/nitrogen analysis apparatus (manufactured by LECO JAPAN CORPORATION.

(Heating Test)

[0083] The sintered body was heat-treated using a hot plate at 250° C. in the air for one hour, and whether metal gallium was deposited from the sintered body or not was visually confirmed.

(Measurement of Particle Size)

[0084] With respect to the particle sizes of the powder and the sintered body, the particle sizes of at least 100 particles were measured from at least two fields of view by the diameter method from images observed with a SEM, and the 50% particle size was taken as the average particle size.

(Confirmation of Crystal Plane, Method of Measuring Half Value Width and Intensity Ratio)

[0085] For usual measurement, a common powder X-ray diffraction apparatus (apparatus name: Ultima III, manufactured by Rigaku Corporation) was used. Conditions of the XRD measurement are as follows.

[0086] Light source: CuKα ray (λ=0.15418 nm)

[0087] Measurement mode: 28/8 scan

[0088] Measurement interval: 0.01°

[0089] Divergence slit: 0.5 deg

[0090] Scattering slit: 0.5 deg

[0091] Receiving slit: 0.3 mm

[0092] Measurement time: 1.0 second

[0093] Measurement range: 2θ=20° to 80°

[0094] To identify the XRD pattern, a XRD analysis software (product name: JADE7, manufactured by Materials Data Incorporated) was used. With respect to the hexagonal crystal, a gallium nitride crystal plane was confirmed with reference to JCPDS No. 00-050-0792, the half value width was measured with respect to the (002) plane, and the intensity ratio is calculated from the following formula with respect to 1(002) and 1(101).

[0095] Intensity ratio=I(002)/I(101)

[0096] In a case where a peak considered to be attributable to the (101) plane is not detected, the background peak intensity at 36 to 37° is regarded as I(101) for calculation.

[0097] For high precision measurement, using an XRD apparatus (manufactured by Bruker Corporation, D8 DISCOVER), CuKα2 was removed, and w scanning was conducted, under conditions of 40 kV and 40 mA, high resolution mode, using Ge(220) monochrometer.

[0098] Light source: CuKα ray (λ=0.15418 nm)

[0099] Monochrometer: Ge(220)

[0100] Path finder: Crystal 3B

[0101] Measurement mode: ω scan

[0102] Measurement interval: 0.01°

(0.0005° in a case where the half value width is at most 0.1°)

[0103] Measurement time: 0.5 second

[0104] Measurement range: ω=0° to 35°

(Measurement of Oxygen Content in Film)

[0105] The oxygen content in the film was measured by a SIMS (secondary ion mass spectrometer). The content of oxygen was measured in the film depth direction, and the minimum content from 5 nm to 30 nm from the interface at a position assumed to be a substrate was calculated.

Examples 1 to 4

[0106] 30 g of a gallium nitride powder as identified in Table 1 was cast in a carbon mold of 52 mm in diameter, and the mold was put in a hot press. Firing was started with an ultimate vacuum as identified in Table 1 before the start of temperature increase, the temperature was increased at 200° C./h finally to the temperature as identified in Table 1, and on that occasion, the pressure was elevated to the pressure as identified in Table 1 when the maximum temperature was held, and hot pressing was conducted while the temperature and the pressure were maintained for one hour. The temperature was decreased to about 50° C. over a period of 5 hours, the mold was taken out, and the sintered body was recovered. The sintered body of at least 10 g was obtained in each Example. Of the obtained polycrystalline gallium nitride sintered body, the weight, the density, the oxygen content, the resistivity, the average particle size and the results of the heating test are shown in Table 2.

[0107] The sintered body was further processed and bonded to a backing plate, and whether it could be used as a sputtering target to form a film by DC or RF was confirmed. As a result, all the samples could be bonded without any problem and could be used for forming a film by DC/RF.

Example 5

[0108] 250 g of a gallium nitride powder as identified in Table 1 was cast in a carbon mold of 130 mm in diameter, and the mold was put in a hot press. Firing was started with an ultimate vacuum before the start of temperature increase as identified in Table 1, the temperature was increased at 200° C./h finally to the temperature as identified in Table 1, and on that occasion, the pressure was elevated to the pressure as identified in Table 1 when the maximum temperature was held, and hot pressing was conducted while the temperature and the pressure were maintained for 2 hours. After the temperature was decreased, the mold was taken out, and the sintered body was recovered. Of the obtained polycrystalline gallium nitride sintered body, the weight, the density, the oxygen content, the resistivity, the average particle size and the results of the heating test are shown in Table 2.

Comparative Examples 1 to 3

[0109] Using the gallium nitride powder as identified in Table 1, hot pressing was conducted under the same temperature-increasing rate, retention time and temperature-decreasing conditions as in Example 1 except for the ultimate vacuum, the firing temperature and the load as identified in Table 1, whereupon the weight, the density, the oxygen content, the resistivity, the average particle size and the results of the heating test of the obtained polycrystalline gallium nitride sintered body were as identified in Table 2. In Comparative Example 2, shape retaining was not possible, and no sintered body could be obtained.

Comparative Example 4

[0110] 24.5 g of a gallium nitride sintered body prepared in the same manner as in Comparative Example 1, and metal gallium (purity: 6N, oxygen content: 0.0174 atm %, manufactured by DOWA Electronics Materials Co, Ltd.) in an amount of 1.35 times the amount of the sintered body, were charged in a vacuum packaging bag and vacuum ized under 1,000 Pa. The packaging bag was heated to about 50° C. to completely melt metal gallium, and charged to CIP and pressurized under 100 MPa for 60 seconds. The mixture was taken out and heated at about 50° C., remaining metal gallium was removed, and a gallium nitride sintered body infiltrated with metal gallium was obtained. The obtained sintered body was subjected to the heating test at 250° C., whereupon deposition of Ga metal was observed. The average particle size shown in Table 2 is the average particle size of the sintered body before infiltration with metal gallium, and the weight, the density, the oxygen content, the resistivity and the results of the heating test were those of the gallium nitride sintered body infiltrated with metal gallium.

Reference Example

[0111] It was attempted to prepare a sintered body infiltrated with metal gallium in the same manner as in Comparative Example 4 using the sintered body prepared in the same manner as in Example 1, however, the sintered body had fractures at the time of infiltration.

TABLE-US-00001 TABLE 1 Physical properties of powder Specific Average Hot pressing conditions surface Oxygen Bulk particle Mold Ultimate area content density size diameter vacuum Firing Temperature Load Examples m.sup.2/g atm % g/cm.sup.3 μm mmφ Pa atmosphere ° C. MPa Ex. 1 0.5 0.7 1 0.8 52 50 Vacuum 1060 50 Ex. 2 0.3 0.5 1.2 0.87 52 0.005 Vacuum 1100 50 Ex. 3 0.3 0.5 1.2 0.87 52 0.004 Vacuum 1150 50 Ex. 4 0.3 0.5 1.2 0.87 52 0.003 Vacuum 1100 100 Ex. 5 0.3 0.5 1.2 0.87 130 0.1 Vacuum 1100 40 Comp. Ex. 1 3.4 3.1 0.9 0.1 130 50 Vacuum 1100 50 Comp. Ex. 2 0.3 0.5 1.2 0.87 52 0.004 Vacuum 1000 50 Comp. Ex. 3 3.4 3.1 0.4 0.1 52 50 Vacuum 900 50 Comp. Ex. 4 3.4 3.1 0.9 0.1 52 50 Vacuum 1000 50

TABLE-US-00002 TABLE 2 Physical properties of sintered body Ga deposition Oxygen Average after heat Weight Density content Resistivity particle size treatment at Discharge Examples g g/cm.sup.3 atm % Ωcm D50 μm 250° C. method Ex. 1 27.9 3.2 0.9 0.03  1 Nil DC/RF Ex. 2 24.9 4.2 0.5 0.007 1.1 Nil DC/RF Ex. 3 14.1 4.5 0.3 0.002 1.3 Nil DC/RF Ex. 4 23.7 4.8 0.4 0.001 1.4 Nil DC/RF Ex. 5 243 3.5 0.4 0.01  1.2 Nil DC/RF Comp. Ex. 1 240 3.2 3.6 4 × 10.sup.5 0.2 Nil RF Comp. Ex. 2 — — — — — — — Comp. Ex. 3 29.4 2.5 3.8 2 × 10.sup.6 0.3 Nil RF Comp. Ex. 4 39 5.1 3.8 0.006 0.1 Observed —

Reference Examples 1 to 23

[0112] A film forming test by sputtering was conducted by using the gallium nitride sputtering target by a magnetron sputtering apparatus under conditions as identified in Table 3.

[0113] As a result of film forming under the above conditions, a gallium nitride thin film as identified in Table 4 was obtained.

TABLE-US-00003 TABLE 3 Physical properties Dis- of target Film charge Dis- Oxygen Ultimate forming Gas introduced electric Discharge Film forming Film charge content Size vacuum pressure Nitrogen Argon power density temperature thickness Ex. method Material atm % mmφ 10.sup.−6 Pa Pa sccm sccm W W/cm.sup.2 ° C. nm Ref. RF GaN 3 120 5.8 0.07 20 0 125 1.1 25 50 Ex. 1 Ref. RF GaN 3 120 4.7 0.1 20 0 250 2.2 200 50 Ex. 2 Ref. RF GaN 3 120 6.1 0.07 20 0 125 1.1 25 300 Ex. 3 Ref. RF GaN 3 120 8.5 0.07 20 0 125 1.1 600 300 Ex. 4 Ref. RF GaN 3 120 23 0.07 20 0 125 1.1 800 1000 Ex. 5 Ref. RF GaN 3 120 4.8 0.07 18 0 250 2.2 25 300 Ex. 6 Ref. RF GaN 3 120 6.8 0.05 10 1 250 2.2 25 50 Ex. 7 Ref. RF GaN 3 120 5.8 0.07 20 2 250 2.2 25 50 Ex. 8 Ref. RF GaN 3 120 5.8 0.07 20 0 75 0.67 25 50 Ex. 9 Ref. RF GaN 0.4 120 3.3 0.07 18 0 125 1.1 25 300 Ex. 10 Ref. RF GaN 0.4 120 7.4 0.07 18 0 125 1.1 300 300 Ex. 11 Ref. RF GaN 0.4 120 12 0.07 18 0 125 1.1 400 300 Ex. 12 Ref. RF GaN 0.4 120 4.7 0.07 18 0 125 1.1 600 300 Ex. 13 Ref. RF GaN 0.4 120 6 0.07 18 0 125 1.1 700 300 Ex. 14 Ref. RF GaN 0.4 120 13 0.07 18 0 125 1.1 800 300 Ex. 15 Ref. RF GaN 0.4 120 19 0.15 30 0 125 1.1 700 300 Ex. 16 Ref. RF GaN 0.4 120 2.8 0.2 30 0 125 1.1 700 300 Ex. 17 Ref. RF GaN 3 76 400 1.5 22 0 100 2.2 25 1000 Ex. 18 Ref. RF GaN 3 76 400 0.3 22 0 100 2.2 25 1000 Ex. 19 Ref. RF GaN 3 120 21 0.3 30 0 250 2.2 25 1000 Ex. 20 Ref. RF GaN 3 120 42 0.3 30 0 250 2.2 800 1000 Ex. 21 Ref. RF GaN 20 120 74 0.07 30 0 250 2.2 25 300 Ex. 22 Ref. RF GaN 30 120 21 0.07 30 0 250 2.2 25 300 Ex. 23

TABLE-US-00004 TABLE 4 5 to 30 nm ω scanning Peak (002) plane oxygen content (002) plane Examples Crystal system intensity ratio half value width ° 10.sup.20 atm/cm.sup.3 half value width ° Ref. Ex. 1 Hexagonal 1600 0.26 25 — Ref. Ex. 2 Hexagonal 1300 0.22 30 — Ref. Ex. 3 Hexagonal 760 0.14 20 1.47 Ref. Ex. 4 Hexagonal 7000 0.12 20 0.6 Ref. Ex. 5 Hexagonal 680 0.13 20 0.84 Ref. Ex. 6 Hexagonal 830 0.15 30 1.12 Ref. Ex. 7 Hexagonal 630 0.27 30 — Ref. Ex. 8 Hexagonal 1100 0.22 20 — Ref. Ex. 9 Hexagonal 840 0.27 22 — Ref. Ex. 10 Hexagonal 2100 0.11 2.4 1.46 Ref. Ex. 11 Hexagonal 1240 0.11 2.7 1.28 Ref. Ex. 12 Hexagonal 3420 0.11 2.6 0.009 Ref. Ex. 13 Hexagonal 2220 0.1 2.4 0.0064 Ref. Ex. 14 Hexagonal 2530 0.1 2.4 0.0009 Ref. Ex. 15 Hexagonal 2630 0.11 2.3 0.0051 Ref. Ex. 16 Hexagonal 2645 0.101 2.3 0.014 Ref. Ex. 17 Hexagonal 3922 0.092 2.4 0.005 Ref. Ex. 18 Hexagonal 0.39 1.3 250 6 Ref. Ex. 19 Hexagonal 20 0.33 200 21 Ref. Ex. 20 Hexagonal 1.6 0.3 60 — Ref. Ex. 21 Hexagonal 6.8 0.18 60 — Ref. Ex. 22 Hexagonal 21 0.85 70 3.7 Ref. Ex. 23 Hexagonal 9.5 1 100 15.9

[0114] Now, measurement examples regarding a laminated film are presented. Various measurement methods for evaluation are as follows.

(Method of Measuring Crystal Orientation and Half Value Width)

[0115] Scanning was conducted at 2θ/ω using an XRD apparatus, and the crystal orientations of gallium nitride and the metal sulfide were identified from the peak positions and main crystal orientations were confirmed. Among them, the half value width at 2θ/ω with respect to a peak corresponding to gallium nitride (110) plane was measured.

(Method of Confirming Rotational Symmetry)

[0116] phi scanning was conducted on the gallium nitride thin film by using an XRD apparatus to confirm the rotational symmetry.

(Method of Measuring Rocking Curve Half Value Width)

[0117] ω scanning was conducted on the gallium nitride (110) plane identified by an XRD apparatus to measure the rocking curve half value width.

(Method of Measuring Oxygen Content in Gallium Nitride Thin Film)

[0118] Using a SIMS (secondary ion mass spectrometer, apparatus name: PHI ADEPT1010), the amount of oxygen from the interface close to the silicon single crystal layer to 50 nm of the gallium nitride thin film was measured, and the minimum value was taken as the oxygen content. The position of 50 nm from the interface was specified by grasping substances in the respective layers from the compositional change by the SIMS measurement.

(Method of Measuring Surface Roughness)

[0119] The surface state was measured within a range of 10 μm square using an AFM apparatus, and the surface roughness with a 10 μm length was measured.

Laminated Film Reference Example 1

[0120] A substrate comprising a Si(100) single crystal substrate of 2 inches in diameter and MnS formed in a thickness of 50 nm was used. MnS was confirmed to be oriented in the (100) plane.

[0121] Further, a GaN thin film was formed on the MnS/Si thin film under the following conditions to form a laminate.

(Sputtering Conditions)

[0122] Discharge method: RF sputtering

[0123] Film forming apparatus: magnetron sputtering apparatus

[0124] Target size: 2 inches in diameter

[0125] Film forming pressure: 1 Pa

[0126] Gas introduced: argon+10 vol % nitrogen

[0127] Discharge power: 100 W

[0128] Substrate temperature: 700° C.

[0129] Film thickness: 10 nm

[0130] The results of various evaluations were as follows.

[0131] Rotational symmetry: four-fold

[0132] GaN orientation plane: (110) plane

[0133] 2θ/ω half value width: 0.7°

[0134] Rocking curve half value width: 3.4°

[0135] Oxygen content: 3×10.sup.21 atm/cm.sup.3

Laminated film Reference Example 2

[0136] On the GaN layer of the laminate obtained in Laminated Film Reference Example 1, a GaN layer was further formed in a thickness of about 1,000 nm by MOCVD method at a substrate temperature of 1,100° C. The results of various evaluations were as follows.

[0137] Rotational symmetry: four-fold

[0138] GaN orientation plane: (110) plane

[0139] Half value width: 0.18°

[0140] Rocking curve half value width: 1.9°

[0141] Oxygen content: 1×10.sup.21 atm/cm.sup.3

Laminated Film Reference Example 3

[0142] A GaN thin film was formed directly on the Si(100) substrate without forming a MnS buffer layer, however, no dense film could be formed.

[0143] The present invention was described in detail with reference to specific embodiments, however, it is obvious for the person skilled in the art that various changes and modifications are possible without departing from the intension and the scope of the present invention.

[0144] The entire disclosures of Japanese Patent Application No. 2015-069913 filed on Mar. 30, 2015, Japanese Patent Application No. 2015-089571 filed on Apr. 24, 2015, Japanese Patent Application No. 2015-150959 filed on Jul. 30, 2015 and Japanese Patent Application No. 2015-152855 filed on July 31, 2015 including specifications, claims and summaries are incorporated herein by reference in their entireties.