Method of manufacturing a semiconductor device

Abstract

To suppress the expansion of stacking faults in SiC semiconductor devices when current is applied.SOLUTION: A semiconductor device 10 has a substrate 12 made of silicon carbide and a semiconductor layer of a first conductivity type provided on a first surface 12a of the substrate 12. A highly concentrated hydrogen region 40 with a hydrogen concentration exceeding 1015 / cm3 over a thickness of 1 μm or more is formed by irradiation with hydrogen ions. At least a portion of the highly concentrated hydrogen region 40 is formed in the semiconductor layer of the first conductivity type.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.

Background Art

[0002] As a material for next-generation power semiconductor devices, silicon carbide (SiC) has attracted attention. For example, an epitaxial layer is formed on an SiC substrate, and a transistor structure is formed in the epitaxial layer. In an SiC semiconductor device, it is known that when a current is applied, injected carriers are trapped by stacking defects in the epitaxial layer, the stacking defect energy decreases, and this leads to the expansion of the stacking defects. The expansion of the stacking defects is regarded as a problem because it leads to an increase in the forward voltage.

[0003] In order to suppress the expansion of stacking defects, a technique has been proposed in which protons are irradiated into an epitaxial layer to generate a lifetime killer, and carrier recombination is promoted before the injected carriers are trapped by the stacking defects.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When attempting to suppress the expansion of stacking defects by generating a lifetime killer, it is necessary to generate the lifetime killer over a wide range in the depth direction in order to promote sufficient carrier recombination. It is necessary to increase the film thickness of the epitaxial layer or irradiate protons over a wide range in the depth direction, which leads to an increase in manufacturing costs.

[0006] One exemplary object of certain aspects of the present invention is to provide a technique for suppressing the expansion of stacking defects when a current is applied to a SiC semiconductor device. **Means for Solving the Problems**

[0007] A method for manufacturing a semiconductor device according to certain aspects of the present invention irradiates a semiconductor device including a substrate made of silicon carbide and a semiconductor layer of a first conductivity type on a first surface of the substrate with hydrogen ions, so that the hydrogen concentration is 10 over a thickness of 1 μm or more. 15 / cm 3 and forms a high-concentration hydrogen region exceeding this. At least a part of the high-concentration hydrogen region is formed within the semiconductor layer of the first conductivity type.

[0008] Another aspect of the present invention is a semiconductor device. This semiconductor device includes a substrate made of silicon carbide, a semiconductor layer of a first conductivity type provided on the substrate, and a high-concentration hydrogen region having a hydrogen concentration exceeding 10 over a thickness of 1 μm or more. At least a part of the high-concentration hydrogen region is formed within the semiconductor layer of the first conductivity type. 15 / cm 3 Any combination of the above components, or components and expressions of the present invention mutually substituted between methods, devices, systems, etc., are also effective as aspects of the present invention.

[0009] **Advantages of the Invention**

[0010] According to certain aspects of the present invention, it is possible to suppress the expansion of stacking defects when a current is applied to a SiC semiconductor device. **Brief Description of the Drawings**

[0011]

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Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the configurations described below are examples and do not limit the scope of the present invention in any way. Also, in the description of the drawings, the same reference numerals are given to the same elements, and redundant descriptions are omitted as appropriate. Further, in the drawings referred to in the following description, the sizes and thicknesses of the respective constituent members are for convenience of explanation and do not necessarily indicate actual dimensions and ratios.

[0013] The outline of this embodiment will be described. This embodiment relates to a SiC semiconductor device including a substrate made of silicon carbide (SiC) and a semiconductor layer of a first conductivity type provided on a first surface of the substrate. In such a SiC semiconductor device, it has been regarded as a problem that stacking defects existing in the vicinity of the interface between the substrate and the semiconductor layer expand when a current is applied, leading to an increase in the forward voltage.

[0014] In this embodiment, hydrogen ions are irradiated near the interface between the substrate and the semiconductor layer, hydrogen is fixed to the partial dislocations that demarcate the stacking defects, and the expansion of the stacking defects during current application is suppressed. By fixing hydrogen to the partial dislocations, it is possible to suppress the trapping of injected carriers by the stacking defects and the reduction of the stacking defect energy.

[0015] According to the findings of the present inventors, by irradiating hydrogen ions, a high-concentration hydrogen region with a hydrogen concentration exceeding 10 15 / cm 3 can be formed over a thickness of 1 μm or more, thereby suppressing the expansion of stacking defects. By forming a high-concentration hydrogen region over a thickness of 1 μm or more, a sufficient amount of hydrogen can be fixed to the partial dislocations that demarcate the stacking defects present near the interface between the substrate and the semiconductor layer, and the expansion of the stacking defects can be preferably suppressed.

[0016] FIG. 1 is a cross-sectional view schematically showing a configuration example of a semiconductor device 10 according to an embodiment. The semiconductor device 10 is a SiC semiconductor device and is a metal-oxide-semiconductor field-effect transistor (MOSFET). The semiconductor device 10 includes a substrate 12, a buffer layer 14, a drift layer 16, a base region 18, a source region 20, a base contact region 22, a gate insulating film 24, a gate electrode 26, an interlayer insulating film 28, a source electrode 30, and a drain electrode 32.

[0017] The substrate 12 is a SiC substrate made of silicon carbide (SiC) of a first conductivity type (e.g., n-type) or a second conductivity type (e.g., p-type). The substrate 12 is, for example, an n-type SiC substrate and is doped with, for example, nitrogen (N) as an n-type impurity. The impurity concentration of the first conductivity type or the second conductivity type of the substrate 12 is 1.0×10 18 / cm 3 or more, and for example, 2.0×10 18 / cm 3 or more and 5.0×10 19 / cm 3 or less. The substrate 12 includes a first surface 12a and a second surface 12b opposite to the first surface 12a. The first surface 12a is, for example, a (0001)Si surface.

[0018] The buffer layer 14 is a first-conductivity-type SiC semiconductor layer that is epitaxially grown on the first surface 12a of the substrate 12. The buffer layer 14 is, for example, an n-type SiC layer and is doped with, for example, nitrogen (N) as an n-type impurity. The impurity concentration of the first conductivity type in the buffer layer 14 is lower than the impurity concentration of the first conductivity type or the second conductivity type in the substrate 12 and higher than the impurity concentration of the first conductivity type in the drift layer 16. The impurity concentration of the first conductivity type in the buffer layer 14 is, for example, 1.0×10 16 / cm 3 or more and 1.0×10 18 / cm 3 or less. The thickness of the buffer layer 14 is 1.0 μm or more and 5.0 μm or less, for example, 1.5 μm or more and 3.0 μm or less, and for example, 2.0 μm.

[0019] The drift layer 16 is a first-conductivity-type SiC semiconductor layer that is epitaxially grown on the buffer layer 14. The drift layer 16 is, for example, an n-type SiC layer and is doped with, for example, nitrogen (N) as an n-type impurity. The impurity concentration of the first conductivity type in the drift layer 16 is lower than the impurity concentration of the first conductivity type in the buffer layer 14. The impurity concentration of the first conductivity type in the drift layer 16 is, for example, 1.0×10 15 / cm 3 or more and 1.0×10 17 / cm 3 or less. The thickness of the drift layer 16 is larger than the thickness of the buffer layer 14. The thickness of the drift layer 16 is 5.0 μm or more and 50 μm or less, for example, 7.5 μm or more and 15 μm or less, and for example, 10 μm.

[0020] The base region 18 is a second-conductivity-type SiC semiconductor region provided on the drift layer 16. The base region 18 is, for example, p-type and is doped with, for example, aluminum (Al) as a p-type impurity. The base region 18 is formed, for example, by irradiating the drift layer 16 with second-conductivity-type impurity ions. The impurity concentration of the second conductivity type in the base region 18 is higher than the impurity concentration of the first conductivity type in the drift layer 16. The impurity concentration of the second conductivity type in the base region 18 is, for example, 1.0×10 16 / cm 3 Above 1.0×10 18 / cm 3 The following applies.

[0021] The source region 20 is a first-conductivity-type SiC semiconductor region provided above the base region 18. The source region 20 is provided adjacent to the gate insulating film 24. The source region 20 is, for example, n-type, and is doped with, for example, nitrogen (N) as an n-type impurity. The source region 20 is formed, for example, by irradiating the drift layer 16 with impurity ions of the first conductivity type. The impurity concentration of the first conductivity type in the source region 20 is higher than that in the drift layer 16. The impurity concentration of the first conductivity type in the source region 20 is 1.0×10 18 / cm 3 or more, for example 2.0×10 18 / cm 3 or more and 5.0×10 19 / cm 3 The following applies.

[0022] The base contact region 22 is a second-conductivity-type SiC semiconductor region provided above the base region 18. The base contact region 22 is provided away from the gate insulating film 24. The base contact region 22 is, for example, p-type, and is doped with, for example, aluminum (Al) as a p-type impurity. The base contact region 22 is formed, for example, by irradiating the drift layer 16 with impurity ions of the second conductivity type. The impurity concentration of the second conductivity type in the base contact region 22 is higher than that in the base region 18 of the second conductivity type. The impurity concentration of the second conductivity type in the base contact region 22 is, for example, 1.0×10 17 / cm 3 or more and 1.0×10 19 / cm 3 The following applies.

[0023] The gate insulating film 24 is provided on the inner wall surface of the gate trench 34. The gate insulating film 24 is provided so as to be adjacent to the drift layer 16, the base region 18, and the source region 20. The gate trench 34 is formed so as to be dug downward from the upper surface 20a of the source region 20 toward the substrate 12. The gate trench 34 is formed so as to penetrate the source region 20 and the base region 18 and reach the upper part of the drift layer 16. The gate insulating film 24 is formed of an oxide material, for example, SiO2.

[0024] The gate electrode 26 is provided so as to fill the inside of the gate insulating film 24 (gate trench 34). The gate electrode 26 is formed of, for example, polycrystalline silicon doped with an n-type impurity such as phosphorus (P) or nitrogen (N).

[0025] The interlayer insulating film 28 is provided on the gate insulating film 24 and the gate electrode 26. The interlayer insulating film 28 is formed of an arbitrary insulating material.

[0026] The source electrode 30 is provided on the source region 20, the base contact region 22, and the interlayer insulating film 28. The source electrode 30 contacts the upper surface 20a of the source region 20 and the upper surface 22a of the base contact region 22. The source electrode 30 is formed of a metal material such as chromium (Cr) or nickel (Ni), for example. The source electrode 30 may be formed of a metal multilayer film in which a plurality of metal layers of different metal materials are laminated. The source electrode 30 is a surface metal electrode layer formed on the surface of the semiconductor device 10.

[0027] The drain electrode 32 is provided on the second surface 12b of the substrate 12. The drain electrode 32 contacts the second surface 12b of the substrate 12. The drain electrode 32 is formed of a metal material such as chromium (Cr) or nickel (Ni), for example. The drain electrode 32 may be formed of a metal multilayer film in which a plurality of metal layers of different metal materials are laminated. The drain electrode 32 is a back surface metal electrode layer formed on the back surface of the semiconductor device 10.

[0028] In the manufacturing process of the semiconductor device 10, the semiconductor device 10 is irradiated with hydrogen ions, and a high-concentration hydrogen region 40 with a hydrogen concentration exceeding 10 15 / cm 3 is formed over a thickness of 1 μm or more. At least a part of the high-concentration hydrogen region 40 is formed in the buffer layer 14 or the drift layer 16, which is a semiconductor layer of the first conductivity type. In the example of FIG. 1, the entire high-concentration hydrogen region 40 is formed in the buffer layer 14, and the upper end 42 and the lower end 44 of the high-concentration hydrogen region 40 are located in the buffer layer 14.

[0029] FIG. 2 is a graph showing an example of the hydrogen concentration of the semiconductor device 10 after hydrogen ion irradiation. FIG. 2 shows the case where the energy of hydrogen ion irradiation is 960 keV and the dose amount is 1.0×10 13 / cm 2 . In the example of FIG. 2, the thickness range of the high-concentration hydrogen region 40 where the hydrogen concentration exceeds 10 15 / cm 3 is about 1.9 μm. In the example of FIG. 2, in the thickness range 46 of about 1.1 μm of the high-concentration hydrogen region 40, the hydrogen concentration exceeds 10 16 / cm 3 . In the example of FIG. 2, the peak value of the hydrogen concentration in the high-concentration hydrogen region 40 is about 1.1×10 17 / cm 3 . By forming such a high-concentration hydrogen region 40 in the buffer layer 14, the expansion of stacking defects when a current is applied to the semiconductor device 10 can be suppressed.

[0030] The presence or absence of the expansion of stacking defects can be confirmed by the X-ray topography method or the photoluminescence method. First, the position of the stacking defects existing in the semiconductor device 10 before current application is confirmed by X-ray topography or photoluminescence, and it can be observed by the X-ray topography or photoluminescence method whether the stacking defects expand after current application. Note that instead of generating injected carriers by applying a current, carriers can be generated by irradiating ultraviolet light, and the presence or absence of the expansion of stacking defects can also be confirmed.

[0031] FIG. 3 is a table showing the thickness of the high-concentration hydrogen region 40 and the presence or absence of the expansion of the stacking defect in the comparative examples and the examples. FIG. 3 summarizes the presence or absence of the expansion of the stacking defect when the dose of hydrogen ion irradiation is changed in the range of 1.0×10 10 / cm 2 ~1.0×10 16 / cm 2 . In Comparative Examples 1 and 2 where the thickness of the high-concentration hydrogen region 40 is less than 1 μm, the expansion of the stacking defect was confirmed. On the other hand, in Examples 1 to 5 where the thickness of the high-concentration hydrogen region 40 is 1 μm or more, the expansion of the stacking defect was not confirmed, so it was found that the expansion of the stacking defect can be suppressed.

[0032] Note that it is considered that the expansion of the stacking defect can be suppressed even when the dose is more than 1.0×10 16 / cm 2 . However, increasing the dose more than 1.0×10 16 / cm 2 is not preferable from the viewpoint of productivity.

[0033] FIGS. 4(a) to 4(d) are diagrams schematically showing another example of the formation positions of the high-concentration hydrogen regions 40a to 40d.

[0034] The high-concentration hydrogen region 40a shown in FIG. 4(a) is formed across the substrate 12 and the buffer layer 14, and is formed across the first surface 12a which is the interface between the substrate 12 and the buffer layer 14. The upper end 42a of the high-concentration hydrogen region 40a is located in the buffer layer 14, and the lower end 44a of the high-concentration hydrogen region 40a is located in the substrate 12. At least a part of the high-concentration hydrogen region 40a is formed in the substrate 12 and the buffer layer 14.

[0035] The high-concentration hydrogen region 40b shown in FIG. 4(b) is formed across the substrate 12, the buffer layer 14, and the drift layer 16. The high-concentration hydrogen region 40b is formed across the first surface 12a which is the interface between the substrate 12 and the buffer layer 14, and is also formed across the interface 36 between the buffer layer 14 and the drift layer 16. The upper end 42b of the high-concentration hydrogen region 40b is located in the drift layer 16, and the lower end 44b of the high-concentration hydrogen region 40b is located in the substrate 12. At least a part of the high-concentration hydrogen region 40b is formed in the substrate 12, the buffer layer 14, and the drift layer 16.

[0036] The high-concentration hydrogen region 40c shown in FIG. 4(c) is formed across the buffer layer 14 and the drift layer 16. The high-concentration hydrogen region 40c is formed across the interface 36 between the buffer layer 14 and the drift layer 16. The upper end 42c of the high-concentration hydrogen region 40c is located in the drift layer 16, and the lower end 44c of the high-concentration hydrogen region 40c is located in the buffer layer 14. At least a part of the high-concentration hydrogen region 40b is formed in the buffer layer 14 and the drift layer 16.

[0037] The high-concentration hydrogen region 40d shown in FIG. 4(d) is formed only in the drift layer 16. The upper end 42d and the lower end 44d of the high-concentration hydrogen region 40d are located in the drift layer 16.

[0038] The high-concentration hydrogen regions 40, 40a to 40d are preferably formed at positions close to the first surface 12a of the substrate 12. At least a part of the high-concentration hydrogen regions 40, 40a to 40d is preferably formed within 5 μm from the first surface 12a of the substrate 12. The upper ends 42, 42a to 42d or the lower ends 44, 44a to 44d of the high-concentration hydrogen regions 40, 40a to 40d are preferably located within 5 μm from the first surface 12a of the substrate 12. The upper ends 42, 42a to 42d or the lower ends 44, 44a to 44d of the high-concentration hydrogen regions 40, 40a to 40d may be formed within 4 μm, 3 μm, or 2 μm from the first surface 12a of the substrate 12.

[0039] The hydrogen concentrations in the high-concentration hydrogen regions 40, 40a to 40d may be subsequently reduced by an annealing process included in the manufacturing process of the semiconductor device 10. For example, when the annealing process is performed after the irradiation of hydrogen ions, hydrogen may diffuse due to the annealing process and the hydrogen concentration may decrease. At this time, the hydrogen fixed to the partial dislocations that demarcate the stacking defect maintains the fixed state even after the annealing process. That is, the hydrogen that diffuses due to the annealing process is not fixed to the partial dislocations that demarcate the stacking defect and is considered not to contribute to the suppression of the expansion of the stacking defect. According to the present embodiment, even if the hydrogen concentration in the buffer layer 14 or the drift layer 16 at the completion of the semiconductor device 10 is 1.0×10 15 / cm 2 or less, if the hydrogen concentration in the buffer layer 14 or the drift layer 16 after the hydrogen ion irradiation exceeds 1.0×10 15 / cm 2 over a thickness of 1 μm or more, the expansion of the stacking defect can be suppressed.

[0040] Note that if the annealing process is not performed after the hydrogen ion irradiation, the hydrogen concentration in the buffer layer 14 or the drift layer 16 of the semiconductor device 10 may remain in a state exceeding 1.0×10 15 / cm 2 In this case, since the high-concentration hydrogen regions 40, 40a to 40d can be formed by the irradiation of hydrogen ions, the expansion of the stacking defect can be suppressed.

[0041] Next, a method for manufacturing the semiconductor device 10 will be described. FIGS. 5 to 11 are cross-sectional views schematically showing the manufacturing process of the semiconductor device.

[0042] First, as shown in FIG. 5, a buffer layer 14 is formed on the first surface 12a of the substrate 12, and a drift layer 16 is formed on the buffer layer 14. The buffer layer 14 and the drift layer 16 can be formed using any epitaxial growth method such as chemical vapor deposition (CVD). The growth temperature of the buffer layer 14 and the drift layer 16 is, for example, 1500° C. or higher and 1700° C. or lower.

[0043] Next, as shown in FIG. 6, hydrogen ions 50 are irradiated from above the drift layer 16 to form a high-concentration hydrogen region 40 in the buffer layer 14. The irradiation of the hydrogen ions 50 can be performed using any ion irradiation device. For example, the hydrogen ions 50 can be irradiated using an ion irradiation device of a cyclotron system or a van de Graaff system. The hydrogen ions 50 may be irradiated from the second surface 12b (back surface) of the substrate 12.

[0044] Next, as shown in FIG. 7, second impurity ions 52 serving as second-conductivity-type impurities are irradiated from above the drift layer 16 to form a base region 18 and a base contact region 22. The second impurity ions 52 are, for example, aluminum ions. The base region 18 can be formed by irradiating the entire surface of the drift layer 16 with the second impurity ions 52. The base contact region 22 can be formed by irradiating the second impurity ions 52 in a state where regions other than the region to be the base contact region 22 are masked.

[0045] Next, as shown in FIG. 8, first impurity ions 54 serving as first-conductivity-type impurities are irradiated from above the drift layer 16 to form a source region 20. The first impurity ions 54 are, for example, nitrogen ions. The source region 20 can be formed by irradiating the first impurity ions 54 in a state where regions other than the region to be the source region 20 (for example, the base contact region 22) are masked.

[0046] Subsequently, an annealing process is performed at a first temperature in order to activate the first-conductivity-type or second-conductivity-type impurities implanted in the base region 18, the source region 20, and the base contact region 22. The first temperature is 1500 ° C. or higher, for example, 1600 ° C. or higher and 1800 ° C. or lower. By performing the annealing process at the first temperature, the lattice defects formed in the buffer layer 14 by the irradiation of the hydrogen ions 50 can be recovered. Further, by performing the annealing process at the first temperature, hydrogen that is not fixed to the partial dislocations that border the extended defects diffuses, and the hydrogen concentration in the high-concentration hydrogen region 40 can decrease to 1 × 10 15 / cm 3 or less.

[0047] Next, as shown in FIG. 9, a gate trench 34 is formed. For example, a mask is formed outside the region where the gate trench 34 is to be formed, and the source region 20, the base region 18, and the drift layer 16 are dry-etched in the opening region of the mask, whereby the gate trench 34 can be formed.

[0048] Subsequently, a gate insulating film 24 is formed on the inner wall surface of the gate trench 34. The gate insulating film 24 can be formed, for example, by thermally oxidizing the inner wall surface of the gate trench 34 at a temperature of about 700°C to 1000°C. Subsequently, a gate electrode 26 is formed inside the gate insulating film 24. The gate electrode 26 can be formed using any technique such as CVD.

[0049] Next, as shown in FIG. 10, an interlayer insulating film 28 is formed on the source region 20, the base contact region 22, the gate insulating film 24, and the gate electrode 26. The interlayer insulating film 28 can be formed using any technique such as CVD. Subsequently, a drain electrode 32 (back surface metal electrode layer) is formed on the second surface 12b of the substrate 12. The drain electrode 32 can be formed using any film formation technique such as sputtering or evaporation.

[0050] After the formation of the drain electrode 32, the drain electrode 32 is annealed at a second temperature to make the drain electrode 32 have an ohmic contact with the second surface 12b of the substrate 12. The second temperature is 450°C or higher, for example, 600°C or higher and 800°C or lower.

[0051] Next, as shown in FIG. 11, a part of the interlayer insulating film 28 is removed to expose the upper surface 20a of the source region 20 and the upper surface 22a of the base contact region 22. Subsequently, the source electrode 30 (surface metal electrode layer) shown in FIG. 1 is formed. The source electrode 30 can be formed using any film formation technique such as sputtering or evaporation.

[0052] After forming the source electrode 30, anneal the source electrode 30 at a third temperature to make the source electrode 30 have an ohmic contact with the source region 20 and the base contact region 22. The third temperature is 300°C or higher, for example, 350°C or higher and 500°C or lower.

[0053] Through the above steps, the semiconductor device 10 in FIG. 1 is completed.

[0054] FIG. 12 is a flowchart showing an example of a manufacturing method of the semiconductor device 10 according to the embodiment. First, form a semiconductor layer of a first conductivity type (for example, a buffer layer 14 and a drift layer 16) on the first surface 12a of the substrate 12 (S10). Next, irradiate with hydrogen ions 50 to form a high-concentration hydrogen region 40 where the hydrogen concentration exceeds 10 15 / cm 3 over a thickness of 1 μm or more (S12). Irradiate with ions 52 of impurities of a second conductivity type to form a base region 18 and a base contact region 22 (S14), and irradiate with ions 54 of impurities of a first conductivity type to form a source region 20 (S16).

[0055] Subsequently, anneal the semiconductor device 10 at a first temperature of 1500°C or higher (S18) to activate the impurities in the base region 18, the source region 20, and the base contact region 22. Next, form a gate trench 34, and form a gate insulating film 24 and a gate electrode 26 in the gate trench 34 (S20). Next, form an interlayer insulating film 28 on the gate electrode 26 (S22).

[0056] Subsequently, form a back metal electrode layer (drain electrode 32) on the second surface 12b of the substrate 12 and anneal it at a second temperature of 450°C or higher (S24). Next, remove a part of the interlayer insulating film 28 (S26), form a surface metal electrode layer (source electrode 30) on the interlayer insulating film 28, and anneal it at a third temperature of 300°C or higher (S28).

[0057] According to the present embodiment, the hydrogen concentration is 10 over a thickness of 1 μm or more 15 / cm 3By irradiating hydrogen ions 50 so that a high-concentration hydrogen region 40 exceeding [the specified value] is formed, the expansion of stacking defects can be suppressed. In particular, it is possible to suppress the upward expansion of stacking defects existing in the buffer layer 14 and the drift layer 16, and to suppress the stacking defects from reaching the base region 18, the source region 20, and the base contact region 22. Thereby, it is possible to suppress a decrease in performance accompanying the energization and use of the semiconductor device 10.

[0058] According to the present embodiment, by performing an annealing process at a first temperature of 1500°C or higher after the irradiation of hydrogen ions 50, it is possible to recover lattice defects formed in the buffer layer 14, the drift layer 16, etc. by the irradiation of hydrogen ions 50. Thereby, it is possible to suppress a decrease in the carrier lifetime due to lattice defects, and to suppress the influence on device characteristics.

[0059] In the flow of FIG. 12, the order of the steps S12 to S16 may be changed. For example, after the irradiation of the second impurity ions 52 in S14, the irradiation of the hydrogen ions 50 in S12 may be performed, or after the irradiation of the first impurity ions 54 in S16, the irradiation of the hydrogen ions 50 in S12 may be performed. Also, after the irradiation of the first impurity ions 54 in S16, the irradiation of the second impurity ions 52 in S14 may be performed.

[0060] In the flow of FIG. 12, the irradiation of the hydrogen ions 50 in S12 may be performed after the annealing process at the first temperature in S18. In this case, the lattice defects generated by the irradiation of the hydrogen ions 50 can be recovered by the annealing process at the second temperature in S24. The irradiation step of the hydrogen ions 50 in S12 may be performed between S18 and S20, between S20 and S22, or between S22 and S24.

[0061] In the flow of FIG. 12, irradiation with 50 hydrogen ions of S12 may be performed after the annealing treatment at the second temperature of S24. In this case, the irradiation step of 50 hydrogen ions of S12 may be performed between S24 and S26, or may be performed between S26 and S28. In this case, since the third temperature of the annealing treatment of S28 is low, diffusion of hydrogen injected into the high-concentration hydrogen region 40 is suppressed. In this case, at the time of completion of the semiconductor device 10, the hydrogen concentration in the high-concentration hydrogen region 40 may be maintained in a state exceeding 1.0×10 15 / cm 2 .

[0062] In the flow of FIG. 12, the order of the steps of S22 to S28 may be changed. For example, after formation of the back surface metal electrode layer (drain electrode 32) of S24, formation of the interlayer insulating film 28 of S22 may be performed. Alternatively, the formation step of the back surface metal electrode layer (drain electrode 32) of S24 may be after the step of S26, or may be after the step of S28.

[0063] In the above-described embodiment, the case where the semiconductor device 10 is a MOSFET has been shown. This embodiment is applicable to SiC semiconductor devices other than MOSFETs as long as they have a laminated structure of a substrate, a buffer layer, and a drift layer. For example, the semiconductor device 10 may be a transistor such as a junction field effect transistor (JFET), a bipolar transistor (BJT), or an insulated gate bipolar transistor (IGBT), or may be a diode such as a Schottky barrier diode or a PIN diode.

[0064] As described above, the present invention has been described based on the embodiments. It should be understood by those skilled in the art that the present invention is not limited to the above-described embodiments, that various design changes are possible, that various modifications are possible, and that such modifications are also within the scope of the present invention.

Description of Reference Numerals

[0065] 10... Semiconductor device, 12... Substrate, 12a... First surface, 12b... Second surface, 14... Buffer layer, 16... Drift layer, 40... High-concentration hydrogen region.

Claims

1. Irradiate a semiconductor device including a substrate made of silicon carbide and a semiconductor layer of a first conductivity type on a first surface of the substrate with hydrogen ions to form a high-concentration hydrogen region having a hydrogen concentration exceeding 10 １５ / cm ３ over a thickness of 1 μm or more, and forming a metal electrode layer on a second surface opposite to the first surface of the substrate; annealing the metal electrode layer at a temperature of 450°C or higher and 800°C or lower; and performing the irradiation of hydrogen ions before annealing at a temperature of 450°C or higher and 800°C or lower, wherein the irradiation of hydrogen ions is performed from above the semiconductor layer, a method for manufacturing a semiconductor device.

2. Irradiating a semiconductor device including a substrate made of silicon carbide and a semiconductor layer of a first conductivity type on a first surface of the substrate with hydrogen ions to form a high-concentration hydrogen region having a hydrogen concentration exceeding 10 １５ / cm ３ over a thickness of 1 μm or more, irradiating ions of impurities of a second conductivity type different from the first conductivity type onto the semiconductor layer; annealing at a temperature of 1500°C or higher to activate the impurities of the second conductivity type; forming a metal electrode layer on a second surface opposite to the first surface of the substrate; annealing the metal electrode layer at a temperature of 450°C or higher and 800°C or lower; and performing the irradiation of hydrogen ions before annealing at a temperature of 450°C or higher and 800°C or lower, wherein the irradiation of hydrogen ions is performed before annealing at a temperature of 1500°C or higher, a method for manufacturing a semiconductor device.

3. The method for manufacturing a semiconductor device according to claim 1 or 2, wherein at least a part of the high-concentration hydrogen region is formed within 5 μm from the first surface.

4. The semiconductor layer of the first conductivity type includes a buffer layer on the substrate and a drift layer of the first conductivity type having a lower impurity concentration than the buffer layer on the buffer layer, The method for manufacturing a semiconductor device according to claim 1 or 2, wherein at least a part of the high-concentration hydrogen region is formed in the buffer layer.

5. The method for manufacturing a semiconductor device according to claim 4, wherein at least a part of the high-concentration hydrogen region is formed at an interface between the substrate and the buffer layer.

6. The semiconductor layer of the first conductivity type includes a buffer layer on the substrate and a drift layer of the first conductivity type having a lower impurity concentration than the buffer layer on the buffer layer, The method for manufacturing a semiconductor device according to claim 1 or 2, wherein at least a part of the high-concentration hydrogen region is formed in the drift layer.

7. The semiconductor layer of the first conductivity type includes a buffer layer on the substrate and a drift layer of the first conductivity type having a lower impurity concentration than the buffer layer on the buffer layer, The method of manufacturing a semiconductor device according to claim 1 or 2, wherein the high-concentration hydrogen region is formed over the buffer layer and the drift layer.

8. The peak value of the hydrogen concentration in the high-concentration hydrogen region is 10 １６ / cm ３ or more, and the manufacturing method of the semiconductor device according to claim 1 or 2, characterized in that it is as described above.

9. The hydrogen concentration in the high-concentration hydrogen region is 10 ２０ / cm ３ The method for manufacturing a semiconductor device according to claim 1 or 2, characterized in that it is as follows.

10. The dose amount of the hydrogen ions is 10 １２ / cm ２ or more, and the method for manufacturing a semiconductor device according to claim 1 or 2, characterized in that.

11. The dose amount of the hydrogen ions is 10 １６ / cm ２ or less, the manufacturing method of the semiconductor device according to claim 10, characterized in that.

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