WO2010058610A1 - 炭化ケイ素半導体装置およびその製造方法 - Google Patents
炭化ケイ素半導体装置およびその製造方法 Download PDFInfo
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- WO2010058610A1 WO2010058610A1 PCT/JP2009/051762 JP2009051762W WO2010058610A1 WO 2010058610 A1 WO2010058610 A1 WO 2010058610A1 JP 2009051762 W JP2009051762 W JP 2009051762W WO 2010058610 A1 WO2010058610 A1 WO 2010058610A1
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- 239000004065 semiconductor Substances 0.000 title claims abstract description 271
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 125
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- H01L29/16—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only elements of Group IV of the Periodic Table
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Definitions
- the present invention relates to a silicon carbide semiconductor device and a method for manufacturing the same, and more specifically to a silicon carbide semiconductor device exhibiting excellent electrical characteristics and a method for manufacturing the same.
- Patent Document 1 a semiconductor device using silicon carbide (SiC) is known (for example, International Publication WO01 / 018872 pamphlet (hereinafter referred to as Patent Document 1)).
- a MOS field effect transistor (MOSFET) as a semiconductor device is formed using a 4H polytype SiC substrate having a plane orientation of approximately ⁇ 03-38 ⁇ .
- the gate oxide film is formed by dry oxidation.
- a large channel mobility about 100 cm 2 / Vs
- the present invention has been made to solve the above problems, and an object of the present invention is to provide a silicon carbide semiconductor device having excellent electrical characteristics such as channel mobility and a method for manufacturing the same. That is.
- the inventor has completed the present invention as a result of earnestly studying the cause of the decrease in channel mobility in order to achieve high channel mobility with high reproducibility in a semiconductor device using SiC as described above. That is, in the above-described semiconductor device, the gate oxide film is formed by dry oxidation, but by such dry oxidation, a trap (interface) is formed at the interface between the gate oxide film and the SiC semiconductor film located under the gate oxide film. Many levels are considered to be formed. The presence of such interface states can be a factor for reducing the above-described channel mobility. This is also estimated from the fact that the threshold voltage of the MOSFET described above is significantly higher than the theoretical value.
- the silicon carbide semiconductor device includes a substrate made of silicon carbide having an off angle of 50 ° or more and 65 ° or less with respect to the plane orientation ⁇ 0001 ⁇ , a semiconductor layer, and an insulating film. Is provided.
- the semiconductor layer is formed on the substrate and is made of silicon carbide.
- the insulating film is formed in contact with the surface of the semiconductor layer.
- the maximum value of the nitrogen atom concentration in a region within 10 nm from the interface between the semiconductor layer and the insulating film is 1 ⁇ 10 21 cm ⁇ 3 or more.
- the silicon carbide semiconductor device includes a substrate made of silicon carbide having an off angle of 50 ° or more and 65 ° or less with respect to the plane orientation ⁇ 0001 ⁇ , a semiconductor layer, and an insulating film.
- the semiconductor layer is formed on the substrate and is made of silicon carbide.
- the insulating film is formed in contact with the surface of the semiconductor layer.
- the maximum value of the hydrogen atom concentration in a region within 10 nm from the interface between the semiconductor layer and the insulating film is 1 ⁇ 10 21 cm ⁇ 3 or more.
- the silicon carbide semiconductor device includes a substrate made of silicon carbide having an off angle of 50 ° or more and 65 ° or less with respect to the plane orientation ⁇ 0001 ⁇ , a semiconductor layer, and an insulating film.
- the semiconductor layer is formed on the substrate and is made of silicon carbide.
- the insulating film is formed in contact with the surface of the semiconductor layer.
- the maximum value of the total concentration of nitrogen atoms and hydrogen atoms in a region within 10 nm from the interface between the semiconductor layer and the insulating film is 1 ⁇ 10 21 cm ⁇ 3 or more.
- carrier mobility in the semiconductor layer in the vicinity of the interface between the insulating film and the semiconductor layer (for example, channel mobility when the insulating film is used as a gate insulating film) It can be made larger than the case where no hydrogen atom is contained, and an on-resistance lower than that of a conventional semiconductor device using silicon can be realized. Therefore, it is possible to obtain a silicon carbide semiconductor device having a sufficiently high carrier mobility (channel mobility) and excellent electrical characteristics.
- the lower limit of the off angle is set to 50 °, as shown in the data described later, from the (01-14) plane having an off angle of 43.3 ° to an (01 ⁇ ) 13)
- a significant increase in carrier mobility was observed with an increase in off-angle toward the surface, and a natural surface was present in the off-angle range between the (01-14) surface and the (01-13) surface. This is because there is no such thing.
- the upper limit of the off-angle is 65 ° because the off-angle increases and the carrier mobility increases from the (01-12) plane with an off-angle of 62.1 ° to the (01-10) plane with an off-angle of 90 °. This is due to the fact that there is a significant decrease in the above-mentioned values and that there is no natural surface in the range of the off angle between the (01-12) surface and the (01-10) surface.
- a step of preparing a substrate made of silicon carbide having an off angle of 50 ° to 65 ° with respect to the plane orientation ⁇ 0001 ⁇ is performed.
- a step of forming a semiconductor layer on the substrate is performed.
- a step of forming an insulating film so as to be in contact with the surface of the semiconductor layer is performed.
- a step of adjusting the nitrogen atom concentration is performed so that the maximum value of the nitrogen atom concentration in a region within 10 nm from the interface between the semiconductor layer and the insulating film is 1 ⁇ 10 21 cm ⁇ 3 or more.
- a step of preparing a substrate made of silicon carbide having an off angle of 50 ° to 65 ° with respect to the plane orientation ⁇ 0001 ⁇ is performed.
- a step of forming a semiconductor layer on the substrate is performed.
- a step of forming an insulating film so as to be in contact with the surface of the semiconductor layer is performed.
- a step of adjusting the hydrogen atom concentration is performed so that the maximum value of the hydrogen atom concentration in a region within 10 nm from the interface between the semiconductor layer and the insulating film is 1 ⁇ 10 21 cm ⁇ 3 or more.
- a step of preparing a substrate made of silicon carbide having an off angle of 50 ° to 65 ° with respect to the plane orientation ⁇ 0001 ⁇ is performed.
- a step of forming a semiconductor layer on the substrate is performed.
- a step of forming an insulating film so as to be in contact with the surface of the semiconductor layer is performed.
- a step of adjusting the total concentration so that the maximum value of the total concentration of nitrogen atoms and hydrogen atoms in a region within 10 nm from the interface between the semiconductor layer and the insulating film is 1 ⁇ 10 21 cm ⁇ 3 or more is performed.
- the silicon carbide semiconductor device with increased carrier mobility (channel mobility) according to the present invention can be easily manufactured.
- a silicon carbide semiconductor device having a high carrier mobility can be obtained.
- FIG. 2 is a flowchart for explaining a method of manufacturing the semiconductor device shown in FIG. It is a cross-sectional schematic diagram for demonstrating each process of the manufacturing method shown in FIG. It is a cross-sectional schematic diagram for demonstrating each process of the manufacturing method shown in FIG. It is a cross-sectional schematic diagram for demonstrating each process of the manufacturing method shown in FIG. It is a cross-sectional schematic diagram for demonstrating each process of the manufacturing method shown in FIG. It is a cross-sectional schematic diagram for demonstrating each process of the manufacturing method shown in FIG. It is a cross-sectional schematic diagram for demonstrating each process of the manufacturing method shown in FIG. It is a cross-sectional schematic diagram which shows Embodiment 2 of the semiconductor device by this invention.
- FIG. 9 is a schematic cross-sectional view for illustrating the method for manufacturing the semiconductor device shown in FIG. 8.
- FIG. 9 is a schematic cross-sectional view for illustrating the method for manufacturing the semiconductor device shown in FIG. 8.
- FIG. 9 is a schematic cross-sectional view for illustrating the method for manufacturing the semiconductor device shown in FIG. 8.
- FIG. 9 is a schematic cross-sectional view for illustrating the method for manufacturing the semiconductor device shown in FIG. 8.
- 14 is a flowchart for explaining a manufacturing method of the semiconductor device shown in FIG. 13; It is a cross-sectional schematic diagram which shows Embodiment 4 of the semiconductor device by this invention.
- 16 is a flowchart for explaining a manufacturing method of the semiconductor device shown in FIG. 15; 17 is a flowchart showing a modification of the method for manufacturing the semiconductor device shown in FIG. It is a graph which shows the nitrogen atom concentration in the depth direction of the sample in Example 1 of this invention. It is a graph which shows the relationship between the value of the peak of the measured nitrogen atom concentration, and channel mobility. It is a graph which shows the relationship between the off-angle of a board
- 10 is a schematic cross-sectional view showing a semiconductor device prepared for measurement in Example 6.
- SYMBOLS 1 Semiconductor device, 2 board
- a semiconductor device 1 shown in FIG. 1 is a lateral MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) as a silicon carbide semiconductor device, and includes a substrate 2 made of silicon carbide (SiC) and a substrate 2.
- An epitaxial layer 3 made of silicon carbide formed, a p-type layer 4 made of silicon carbide formed on the epitaxial layer 3, and an n + region 5 formed on the surface of the p-type layer 4 at an interval; 6, oxide film 8 as a gate insulating film located on the channel region between n + regions 5 and 6, gate electrode 10 formed on oxide film 8, and n + regions 5 and 6.
- a source electrode 11 and a drain electrode 12 formed on each are provided.
- the substrate 2 is a substrate whose main surface is a (03-38) plane having an off angle of about 53 ° with respect to the plane orientation ⁇ 0001 ⁇ .
- the substrate 2 contains n-type conductive impurities.
- the epitaxial layer 3 made of silicon carbide formed on the substrate 2 is an undoped layer.
- the p-type layer 4 formed on the epitaxial layer 3 contains p-type conductive impurities.
- the n + regions 5 and 6 are implanted with n-type conductive impurities.
- Oxide films 7 and 8 are formed so as to cover p-type layer 4 and n + regions 5 and 6. Openings are formed in the oxide films 7 and 8 in regions located on the n + regions 5 and 6. Inside the opening, a source electrode 11 and a drain electrode 12 electrically connected to each of the n + regions 5 and 6 are formed.
- a gate electrode 10 is disposed on the oxide film 8 that acts as a gate insulating film.
- the channel length L g which is the distance between the n + regions 5 and 6 can be set to about 100 ⁇ m, for example.
- the channel width may be, for example, about 2 times the channel length L g (about 200 [mu] m).
- the maximum value of the nitrogen atom concentration in the region within 10 nm from the interface between the p-type layer 4 as the semiconductor layer and the oxide film 8 is 1 ⁇ 10 21 cm ⁇ 3 or more.
- the mobility (channel mobility) in the channel region having the channel length L g (the region between the n + regions 5 and 6 in the p-type layer 4) can be made sufficiently large.
- the interface state density at 0.1 eV below the conduction band is smaller than 1 ⁇ 10 12 cm ⁇ 2 eV ⁇ 1 .
- a substrate preparation step (S10) is performed.
- an n-type silicon carbide substrate having a plane orientation (03-38) plane as the main surface is prepared as the substrate 2.
- Such a substrate can be obtained by, for example, a method of cutting a substrate from an ingot having the (0001) plane as the main surface so that the (03-38) plane is exposed as the main surface.
- an epitaxial layer forming step (S20) is performed. Specifically, as shown in FIG. 3, an undoped silicon carbide epitaxial layer 3 is formed on the substrate 2.
- an injection step (S30) is performed. Specifically, first, a p-type layer 4 is formed as shown in FIG. 4 by injecting a conductive impurity (for example, aluminum (Al)) having p-type conductivity into the epitaxial layer 3. Next, n + regions 5 and 6 are formed as shown in FIG. 5 by implanting an impurity having n type conductivity.
- a conductive impurity for example, aluminum (Al)
- n + regions 5 and 6 are formed as shown in FIG. 5 by implanting an impurity having n type conductivity.
- the n-type conductive impurity for example, phosphorus (P) can be used.
- any conventionally known method can be used.
- the opening having the same planar shape pattern as the planar shape pattern of the region where the n + regions 5 and 6 are to be formed by photolithography and etching Is formed on the oxide film. Further, conductive impurities are implanted using the oxide film on which this pattern is formed as a mask. In this way, the n + regions 5 and 6 described above can be formed.
- an activation annealing process is performed to activate the implanted impurities.
- this activation annealing treatment for example, conditions where the heating temperature is 1700 ° C. and the heating time is 30 minutes may be used.
- a gate insulating film forming step (S40) is performed. Specifically, after sacrificial oxidation treatment is performed on the upper surfaces of the p-type layer 4 and the n + regions 5 and 6, an oxide film 7 as a gate insulating film is formed as shown in FIG. As the thickness of the oxide film 7, for example, a value of 40 nm can be used.
- a nitrogen annealing step (S50) is performed as shown in FIG. Specifically, heat treatment is performed using nitrogen monoxide (NO) gas as the atmospheric gas.
- NO nitrogen monoxide
- conditions for this heat treatment for example, a condition in which the heating temperature is 1100 ° C. and the heating time is 1 hour can be used.
- nitrogen atoms can be introduced into the interface region between oxide film 7 and p-type layer 4 and n + regions 5 and 6.
- an annealing process using an inert gas for example, an annealing process using argon (Ar) gas as the atmospheric gas is performed. May be.
- an electrode formation step (S60) is performed as shown in FIG. Specifically, a resist film having a pattern is formed on the oxide film 7 by photolithography. Using this resist film as a mask, the oxide film 7 is partially removed to form an opening 15 in a region located above the n + regions 5 and 6. Inside the opening 15, a conductor film to be the source electrode 11 and the drain electrode 12 is formed as shown in FIG. This conductor film is formed with the above-described resist film remaining. Thereafter, the resist film is removed, and the conductive film located on the oxide film 7 is removed (lifted off) together with the resist film, whereby the source electrode 11 and the drain electrode 12 can be formed as shown in FIG. it can. At this time, the oxide film 8 (a part of the oxide film 7 shown in FIG. 6) located between the source electrode 11 and the drain electrode 12 becomes a gate insulating film of the semiconductor device to be formed.
- a gate electrode 10 (see FIG. 1) is further formed on the oxide film 8 acting as a gate insulating film.
- the following method can be used. For example, a resist film having an opening pattern located in a region on the oxide film 8 is formed in advance, and a conductor film constituting the gate electrode is formed so as to cover the entire surface of the resist film. Then, by removing the resist film, the conductor film other than the portion of the conductor film to be the gate electrode is removed (lifted off). As a result, the gate electrode 10 is formed as shown in FIG. In this way, a semiconductor device as shown in FIG. 1 can be obtained.
- a semiconductor device 1 is a vertical DiMOSFET (Double Implanted MOSFET), and includes a substrate 2, a buffer layer 21, a breakdown voltage holding layer 22, a p region 23, an n + region 24, and a p +.
- the region 25, the oxide film 26, the source electrode 11 and the upper source electrode 27, the gate electrode 10, and the drain electrode 12 formed on the back side of the substrate 2 are provided.
- the buffer layer 21 made of silicon carbide is formed on the surface of the substrate 2 made of silicon carbide of n conductivity type.
- Buffer layer 21 is n-type in conductivity type and has a thickness of 0.5 ⁇ m, for example.
- the concentration of the n-type conductive impurity in the buffer layer can be set to 5 ⁇ 10 17 cm ⁇ 3 , for example.
- a breakdown voltage holding layer 22 is formed on the buffer layer 21.
- the breakdown voltage holding layer 22 is made of silicon carbide of n-type conductivity, and has a thickness of 10 ⁇ m, for example. Further, as the concentration of the n-type conductive impurity in the breakdown voltage holding layer 22, a value of 5 ⁇ 10 15 cm ⁇ 3 can be used.
- p regions 23 having a p-type conductivity are formed at intervals. Inside the p region 23, an n + region 24 is formed in the surface layer of the p region 23. A p + region 25 is formed at a position adjacent to the n + region 24. From the n + region 24 in one p region 23 to the p region 23, the breakdown voltage holding layer 22 exposed between the two p regions 23, the other p region 23, and the n + region 24 in the other p region 23 An oxide film 26 is formed so as to extend up to. A gate electrode 10 is formed on the oxide film 26. Further, the source electrode 11 is formed on the n + region 24 and the p + region 25. An upper source electrode 27 is formed on the source electrode 11. In the substrate 2, the drain electrode 12 is formed on the back surface opposite to the surface on which the buffer layer 21 is formed.
- the maximum value of the nitrogen atom concentration in the region within 10 nm from the interface between the oxide film 26 and the n + region 24, p + region 25, p region 23 and the breakdown voltage holding layer 22 as the semiconductor layer is 1 ⁇ 10 21 cm ⁇ 3. That's it.
- the mobility of the channel region under the oxide film 26 (part of the p region 23 that is in contact with the oxide film 26 and between the n + region 24 and the breakdown voltage holding layer 22) is shown in FIG. This can be improved in the same manner as the semiconductor device shown in FIG.
- the interface state density at 0.1 eV below the conduction band is smaller than 1 ⁇ 10 12 cm ⁇ 2 eV ⁇ 1 .
- the substrate preparation step (S10) is performed in the same manner as in the semiconductor device manufacturing method shown in FIG.
- substrate 2 made of silicon carbide having a (03-38) plane as a main surface is prepared.
- the substrate 2 for example, a substrate having an n-type conductivity and a substrate resistance of 0.02 ⁇ cm may be used.
- an epitaxial layer forming step (S20) is performed. Specifically, the buffer layer 21 is formed on the surface of the substrate 2.
- an epitaxial layer made of silicon carbide of n-type conductivity for example, having a thickness of 0.5 ⁇ m is formed. For example, a value of 5 ⁇ 10 17 cm ⁇ 3 can be used as the concentration of the conductive impurity in the buffer layer 21.
- a breakdown voltage holding layer 22 is formed on the buffer layer 21 as shown in FIG.
- a layer made of silicon carbide of n-type conductivity is formed by an epitaxial growth method. For example, a value of 10 ⁇ m can be used as the thickness of the breakdown voltage holding layer 22.
- concentration of the n-type conductive impurity in the breakdown voltage holding layer 22 for example, a value of 5 ⁇ 10 15 cm ⁇ 3 can be used.
- an implantation step (S30) is performed in the same manner as the step shown in FIG. Specifically, by using an oxide film formed by photolithography and etching as a mask, an impurity having a conductivity type of p-type is implanted into the breakdown voltage holding layer 22, thereby forming the p region 23 as shown in FIG. Form. Further, after removing the used oxide film, an oxide film having a new pattern is formed again by photolithography and etching. Then, using the oxide film as a mask, an n-type conductive impurity is implanted into a predetermined region, thereby forming an n + region 24. Further, p @ + region 25 is formed by implanting a p-type conductive impurity by the same method. As a result, a structure as shown in FIG. 10 is obtained.
- activation annealing is performed.
- this activation annealing treatment for example, argon gas is used as an atmospheric gas, and conditions such as a heating temperature of 1700 ° C. and a heating time of 30 minutes can be used.
- a gate insulating film forming step (S40) is performed as in the step shown in FIG. Specifically, as shown in FIG. 11, an oxide film 26 is formed so as to cover the breakdown voltage holding layer 22, the p region 23, the n + region 24, and the p + region 25.
- a condition for forming this oxide film 26 for example, dry oxidation (thermal oxidation) may be performed.
- dry oxidation thermal oxidation
- conditions for this dry oxidation conditions such as a heating temperature of 1200 ° C. and a heating time of 30 minutes can be used.
- a nitrogen annealing step (S50) is performed as in the step shown in FIG. Specifically, the annealing process is performed using nitrogen monoxide (NO) as the atmosphere gas.
- NO nitrogen monoxide
- the heating temperature is 1100 ° C. and the heating time is 120 minutes.
- nitrogen atoms are introduced near the interface between the oxide film 26 and the underlying breakdown voltage holding layer 22, p region 23, n + region 24, and p + region 25.
- annealing using nitrogen monoxide as an atmospheric gas annealing using nitrogen monoxide as an atmospheric gas.
- argon (Ar) gas which is an inert gas may be performed.
- argon gas may be used as the atmosphere gas
- the heating temperature may be 1100 ° C. and the heating time may be 60 minutes.
- an electrode formation step (S60) is performed in the same manner as the step shown in FIG. Specifically, a resist film having a pattern is formed on the oxide film 26 by using a photolithography method. Using the resist film as a mask, portions of the oxide film located on n + region 24 and p + region 25 are removed by etching. Thereafter, a conductor film such as a metal is formed so as to be in contact with n + region 24 and p + region 25 on the resist film and inside the opening formed in oxide film 26. Thereafter, by removing the resist film, the conductor film located on the resist film is removed (lifted off).
- nickel (Ni) can be used as the conductor.
- the source electrode 11 and the drain electrode 12 can be obtained as shown in FIG.
- an argon (Ar) gas that is an inert gas is used as the atmosphere gas, and a heat treatment (alloying treatment) is performed with a heating temperature of 950 ° C. and a heating time of 2 minutes.
- the upper source electrode 27 (see FIG. 8) is formed on the source electrode 11. Further, the drain electrode 12 (see FIG. 8) is formed on the back surface of the substrate 2. In this way, the semiconductor device shown in FIG. 8 can be obtained.
- a semiconductor device 1 according to the present invention basically has the same configuration as that of the semiconductor device 1 shown in FIG. 1, but an interface between a p-type layer 4 as a semiconductor layer and an oxide film 8. 1 differs from the semiconductor device 1 shown in FIG. 1 in that the maximum value of the hydrogen atom concentration is 1 ⁇ 10 21 cm ⁇ 3 or more in the boundary region 41 including the region within 10 nm from the region. Even in this case, similarly to the semiconductor device shown in FIG. 1, the mobility (channel mobility) in the channel region including the boundary region 41 can be set to a sufficiently large value. In the semiconductor device 1 shown in FIG.
- the hydrogen atoms contained in the boundary region 41 are in a region within 10 nm from the interface between the p-type layer 4 and the oxide film 8 of the semiconductor device 1 shown in FIG. 1. This is presumably because the interface state is reduced similarly to the nitrogen atom contained. That is, also in the semiconductor device shown in FIG. 13, the interface state density at 0.1 eV below the conduction band is smaller than 1 ⁇ 10 12 cm ⁇ 2 eV ⁇ 1 .
- the manufacturing method of Embodiment 3 of the semiconductor device by this invention is demonstrated.
- the manufacturing method of the semiconductor device shown in FIG. 14 is basically the same as the manufacturing method of the semiconductor device shown in FIG. 2, but a hydrogen annealing step (S70) is performed instead of the nitrogen annealing step (S50) in FIG.
- a hydrogen annealing step (S70) is performed instead of the nitrogen annealing step (S50) in FIG.
- the substrate preparation step (S10), the epitaxial layer formation step (S20), the implantation step (S30), and the gate insulating film formation step (S40) are performed as in the manufacturing method shown in FIG.
- a hydrogen annealing step (S70) is performed.
- heat treatment is performed using hydrogen gas (H 2 ) gas as the atmosphere gas.
- a condition in which the heating temperature is 1100 ° C. and the heating time is 1 hour can be used.
- hydrogen atoms can be introduced into the interface region between oxide film 7 and p-type layer 4 and n + regions 5 and 6.
- an annealing process using an inert gas for example, an annealing process using argon (Ar) gas as the atmosphere gas is performed. May be.
- water vapor or water vapor-containing hydrogen gas may be used as the atmospheric gas instead of hydrogen gas.
- the semiconductor device 1 shown in FIG. 13 can be obtained by performing the electrode forming step (S60) in the same manner as the manufacturing method shown in FIG.
- the semiconductor device 1 basically has the same configuration as that of the semiconductor device 1 shown in FIG. 1, but the interface between the p-type layer 4 and the oxide film 8 as a semiconductor layer. 1 differs from the semiconductor device 1 shown in FIG. 1 in that the maximum value of the total concentration of nitrogen atoms and hydrogen atoms is 1 ⁇ 10 21 cm ⁇ 3 or more in the boundary region 51 including the region within 10 nm from the region. Even in this case, similarly to the semiconductor device shown in FIG. 1, the mobility (channel mobility) in the channel region including the boundary region 41 can be set to a sufficiently large value. Also in the semiconductor device shown in FIG. 15, the interface state density at 0.1 eV below the conduction band is smaller than 1 ⁇ 10 12 cm ⁇ 2 eV ⁇ 1 .
- the manufacturing method of Embodiment 4 of the semiconductor device by this invention is demonstrated.
- the manufacturing method of the semiconductor device shown in FIG. 16 is basically the same as the manufacturing method of the semiconductor device shown in FIG. 2, but after the nitrogen annealing step (S50) in FIG.
- the hydrogen annealing step (S70) is performed before ().
- the substrate preparation step (S10), the epitaxial layer formation step (S20), the implantation step (S30), the gate insulating film formation step (S40), the nitrogen annealing step ( S50) is carried out. Thereafter, a hydrogen annealing step (S70) is performed.
- this step (S70) the same conditions (annealing conditions using hydrogen gas) as in the hydrogen annealing step (S70) in the manufacturing method of Embodiment 3 can be used.
- nitrogen atoms and hydrogen atoms can be introduced into the interface region between oxide film 7 and p-type layer 4 and n + regions 5 and 6.
- water vapor or water vapor-containing oxygen gas may be used as the atmospheric gas instead of hydrogen gas.
- the hydrogen annealing step (S70) may be performed prior to the nitrogen annealing step (S50).
- the hydrogen annealing step (S70) and the nitrogen annealing step (S50) may be performed simultaneously by performing a heat treatment using an atmosphere gas containing hydrogen atoms and nitrogen atoms.
- the semiconductor device 1 shown in FIG. 15 can be obtained by performing the electrode forming step (S60) in the same manner as the manufacturing method shown in FIG.
- the manufacturing method of the semiconductor device shown in FIG. 17 is basically the same as the manufacturing method of the semiconductor device shown in FIG. 16, but after the hydrogen annealing step (S70) in FIG. ) Is different in that a post heat treatment step (S80) is performed. Specifically, similarly to the manufacturing method shown in FIG. 16, the substrate preparation step (S10), the epitaxial layer formation step (S20), the implantation step (S30), the gate insulating film formation step (S40), the nitrogen annealing step ( S50), a hydrogen annealing step (S70) is performed. Thereafter, a post heat treatment step (S80) is performed. Specifically, an annealing process using an inert gas is performed.
- an inert gas for example, argon (Ar)
- the heating temperature is 1100 ° C.
- the heating time is 60 minutes.
- the semiconductor device 1 shown in FIG. 15 can be obtained by performing the electrode forming step (S60) in the same manner as the manufacturing method shown in FIG.
- a heat treatment step similar to the above-described post heat treatment step (S80) may be additionally performed between the nitrogen annealing step (S50) and the hydrogen annealing step (S70).
- the hydrogen annealing step (S70) may be performed prior to the nitrogen annealing step (S50).
- the hydrogen annealing step (S70) and the nitrogen annealing step (S50) may be performed simultaneously by performing a heat treatment using an atmosphere gas containing hydrogen atoms and nitrogen atoms.
- the lateral MOSFET is shown as the semiconductor device 1.
- the features of the third and fourth embodiments may be applied to the vertical DiMOSFET shown in FIG. That is, in the semiconductor device 1 shown in FIG. 8, hydrogen atoms in a region within 10 nm from the interface between the oxide film 26 and the n + region 24, p + region 25, p region 23, and breakdown voltage holding layer 22 as semiconductor layers.
- the maximum value of the concentration or the maximum value of the total concentration of nitrogen atoms and hydrogen atoms can be 1 ⁇ 10 21 cm ⁇ 3 or more.
- the off orientation of the substrate 2 is in the range of ⁇ 11-20> ⁇ 5 ° or less, or the off orientation of the substrate 2 is ⁇ The range is preferably within the range of 01-10> direction ⁇ 5 ° or less.
- the surface orientation of the main surface of the substrate 2 is -3 ° or more and + 5 ° or less with respect to the surface orientation ⁇ 03-38 ⁇ . It is more preferable that
- a semiconductor device 1 as a silicon carbide semiconductor device includes a substrate 2 made of silicon carbide having an off angle of 50 ° or more and 65 ° or less with respect to the plane orientation ⁇ 0001 ⁇ , and a semiconductor layer (p in FIG. 1).
- the mold layer 4 includes a p region 23 in FIG. 8 and an insulating film (the oxide film 8 in FIG. 1 and the oxide film 26 in FIG. 8).
- the semiconductor layer (p-type layer 4, p region 23) is formed on the substrate 2 and is made of silicon carbide.
- the insulating films (oxide films 8 and 26) are formed in contact with the surface of the semiconductor layer (p-type layer 4 including channel region, p region 23).
- the maximum value of the nitrogen atom concentration in a region within 10 nm from the interface between the semiconductor layer and the insulating film (interface between the channel region and the oxide films 8 and 26) is 1 ⁇ 10 21 cm ⁇ 3 or more.
- the carrier mobility (channel mobility) in the channel region in the vicinity of the interface between the oxide films 8 and 26 acting as the gate insulating film and the channel region is not included in the vicinity of the interface. It is possible to realize a lower on-resistance than a conventional semiconductor device using silicon. For this reason, it is possible to obtain a semiconductor device 1 that exhibits sufficiently large channel mobility and excellent electrical characteristics.
- the maximum value of the nitrogen atom concentration is set to 1 ⁇ 10 21 cm ⁇ 3 or more because the channel mobility is a practically sufficient value by setting the nitrogen atom concentration to the above value or more. It is because it can be set to 2 / Vs or more.
- hydrogen atoms are contained in a region within 10 nm from the interface between the semiconductor layer (p-type layer 4 in FIG. 1 and p region 23 in FIG. 8) and the insulating film (oxide films 8 and 26). May be. In this case, the interface state in the region can be more reliably reduced.
- a semiconductor device 1 as a silicon carbide semiconductor device includes a substrate 2 made of silicon carbide having an off angle of 50 ° to 65 ° with respect to the plane orientation ⁇ 0001 ⁇ , and a semiconductor layer (p in FIG. 13).
- the mold layer 4 includes a p region 23 in FIG. 8 and an insulating film (the oxide film 8 in FIG. 13 and the oxide film 26 in FIG. 8).
- the semiconductor layer (p-type layer 4, p region 23) is formed on the substrate 2 and is made of silicon carbide.
- the insulating films (oxide films 8 and 26) are formed in contact with the surface of the semiconductor layer (p-type layer 4 including channel region, p region 23).
- the maximum value of the hydrogen atom concentration in a region within 10 nm from the interface between the semiconductor layer and the insulating film is 1 ⁇ 10 21 cm. -3 or higher.
- the carrier mobility in the channel region in the vicinity of the interface between the oxide films 8 and 26 acting as the gate insulating film and the channel region is made larger than in the case where hydrogen atoms are not contained in the vicinity of the interface, Lower on-resistance than conventional semiconductor devices using silicon can be realized.
- the maximum value of the hydrogen atom concentration is set to 1 ⁇ 10 21 cm ⁇ 3 or more because the channel mobility is a practically sufficient value by setting the hydrogen atom concentration to the above value or more. It is because it can be set to 2 / Vs or more.
- a semiconductor device 1 as a silicon carbide semiconductor device includes a substrate 2 made of silicon carbide having an off angle of 50 ° or more and 65 ° or less with respect to the plane orientation ⁇ 0001 ⁇ , and a semiconductor layer (p in FIG. 15).
- the mold layer 4 includes a p region 23 in FIG. 8 and an insulating film (the oxide film 8 in FIG. 15 and the oxide film 26 in FIG. 8).
- the semiconductor layer (p-type layer 4, p region 23) is formed on the substrate 2 and is made of silicon carbide.
- the insulating films (oxide films 8 and 26) are formed in contact with the surface of the semiconductor layer (p-type layer 4 including channel region, p region 23).
- the maximum value of the total concentration of nitrogen atoms and hydrogen atoms in a region within 10 nm from the interface between the semiconductor layer and the insulating film is 1 ⁇ 10 21 cm ⁇ 3 or more.
- the carrier mobility in the channel region in the vicinity of the interface between the oxide films 8 and 26 acting as the gate insulating film and the channel region can be made higher than in the case where nitrogen and hydrogen atoms are not included in the vicinity of the interface.
- the on-resistance can be increased and lower than that of a conventional semiconductor device using silicon. Note that, as described above, the maximum value of the total concentration of nitrogen atoms and hydrogen atoms is set to 1 ⁇ 10 21 cm ⁇ 3 or more because channel mobility is practically sufficient when the total concentration is set to the above value or more. It is because it can be set to 50 cm 2 / Vs or more which is a small value.
- the interface state density at 0.1 eV below the conduction band is preferably smaller than 1 ⁇ 10 12 cm ⁇ 2 eV ⁇ 1 .
- carrier mobility in the channel region can be sufficiently increased by setting the interface state density as described above.
- the interface state density is higher than 1 ⁇ 10 12 cm ⁇ 2 eV ⁇ 1
- the channel mobility in the semiconductor device 1 is 50 cm 2 / Vs, which is considered to be a practically sufficient value. Therefore, the value of the interface state density is preferably smaller than 1 ⁇ 10 12 cm ⁇ 2 eV ⁇ 1 as described above.
- the off orientation of the substrate 2 may be in the range of ⁇ 11-20> direction ⁇ 5 ° or less.
- the substrate 2 made of silicon carbide may be a 4H polytype SiC substrate.
- the off orientation of the substrate 2 may be in a range of ⁇ 5 ° or less in the ⁇ 01-10> direction.
- the above-described off orientation is a typical off orientation in a 4H polytype SiC substrate, and an epitaxial layer can be easily formed on the SiC substrate.
- the reason why the range of the off orientation is set to ⁇ 5 ° or less is that the processing variation at the time of slicing the substrate is taken into consideration.
- the surface orientation of the main surface of the substrate 2 may be an off angle of ⁇ 3 ° to + 5 ° with respect to the surface orientation ⁇ 03-38 ⁇ . More preferably, the plane orientation of the main surface of the substrate is substantially ⁇ 03-38 ⁇ , and more preferably the plane orientation of the main surface of the substrate is ⁇ 03-38 ⁇ .
- the main surface of the substrate being substantially ⁇ 03-38 ⁇ means that the main surface of the substrate is within an off-angle range in which the plane orientation can be substantially regarded as ⁇ 03-38 ⁇ due to the processing accuracy of the substrate.
- the plane orientation is included, and the range of the off angle in this case is, for example, a range where the off angle is ⁇ 2 ° with respect to ⁇ 03-38 ⁇ .
- the above-described carrier mobility channel mobility
- the range of the off angle in an arbitrary direction with respect to the plane orientation ⁇ 03-38 ⁇ is set to ⁇ 3 ° or more and + 5 ° or less is that, as will be apparent from the data described later, good carrier mobility (channel movement) This is because the range of the off angle showing the channel mobility of about 90 cm 2 / Vs or more, which is considered to be (degree), is considered to be at least the above range.
- a step of preparing a substrate 2 made of silicon carbide having an off angle of 50 ° to 65 ° with respect to the plane orientation ⁇ 0001 ⁇ substrate preparation step (S10 )).
- a step of forming a semiconductor layer on the substrate 2 is performed.
- a step of forming an insulating film so as to be in contact with the surface of the semiconductor layer is performed.
- a step of adjusting the nitrogen atom concentration (nitrogen annealing step (S50)) so that the maximum value of the nitrogen atom concentration in the region within 10 nm from the interface between the semiconductor layer and the insulating film is 1 ⁇ 10 21 cm ⁇ 3 or more is performed. To do. In this way, the semiconductor device 1 with increased carrier mobility (channel mobility) according to the present invention can be easily manufactured.
- the method for manufacturing the silicon carbide semiconductor device includes a step of containing hydrogen atoms in a region within 10 nm from the interface between the semiconductor layer (p-type layer 4, p region 23) and the insulating film (oxide films 8, 26) (for example, FIG. 16 or the hydrogen annealing step (S70) of FIG. 17 may be further provided.
- a silicon carbide semiconductor device containing hydrogen atoms in addition to nitrogen atoms can be easily manufactured in the above region.
- the step of containing hydrogen atoms (hydrogen annealing step (S70)) is performed by applying a gas containing hydrogen atoms to the substrate on which the insulating films (oxide films 8 and 26) are formed. Including a step of heat treatment using the gas. In this case, the hydrogen atom concentration in the vicinity of the interface between the semiconductor layer (p-type layer 4 including channel region, p region 23) and oxide films 8 and 26 can be easily adjusted.
- the step of containing hydrogen atoms includes a step of performing heat treatment using a gas containing hydrogen atoms as an atmospheric gas, and then using an inert gas as an atmospheric gas. And a step of heat-treating the substrate.
- the carrier mobility of the semiconductor device 1 can be further increased.
- the nitrogen annealing step (S50) is a step of heat-treating the substrate 2 on which the insulating films (oxide films 8 and 26) are formed using a gas containing nitrogen atoms as an atmospheric gas. May be included. In this case, the nitrogen atom concentration in the vicinity of the interface between the semiconductor layer (the p-type layer 4 including the channel region and the p region 23) and the oxide films 8 and 26 can be easily adjusted.
- the nitrogen annealing step (S50) uses an inert gas (Ar gas) as the atmospheric gas after the above-described heat treatment using the gas containing nitrogen atoms as the atmospheric gas.
- a step of heat-treating the substrate 2 may be included. In this case, the carrier mobility of the semiconductor device 1 can be further increased.
- a step of preparing a substrate 2 made of silicon carbide having an off angle of 50 ° to 65 ° with respect to the plane orientation ⁇ 0001 ⁇ substrate preparation step (S10 )).
- a step of forming a semiconductor layer on the substrate 2 is performed.
- a step of forming an insulating film so as to be in contact with the surface of the semiconductor layer is performed.
- a step of adjusting the hydrogen atom concentration (hydrogen annealing step (S70)) so that the maximum value of the hydrogen atom concentration in the region within 10 nm from the interface between the semiconductor layer and the insulating film is 1 ⁇ 10 21 cm ⁇ 3 or more. carry out. In this way, the semiconductor device 1 with increased carrier mobility (channel mobility) according to the present invention can be easily manufactured.
- the method for manufacturing the silicon carbide semiconductor device includes a step of containing nitrogen atoms in a region within 10 nm from the interface between the semiconductor layer (p-type layer 4 and p region 23) and the insulating film (oxide films 8 and 26) (nitrogen annealing). Step (S50)) may be further provided.
- a silicon carbide semiconductor device containing nitrogen atoms in addition to hydrogen atoms can be easily manufactured in the above region.
- the step of containing nitrogen atoms is performed by applying a gas containing nitrogen atoms to the substrate on which the insulating films (oxide films 8 and 26) are formed. Including a step of heat treatment using the gas.
- the nitrogen atom concentration in the vicinity of the interface between the semiconductor layer (the p-type layer 4 including the channel region and the p region 23) and the oxide films 8 and 26 can be easily adjusted.
- the step of containing nitrogen atoms includes a step of performing heat treatment using a gas containing nitrogen atoms as an atmospheric gas, and then using an inert gas as an atmospheric gas. And the step of heat-treating the substrate may be included. In this case, the carrier mobility of the semiconductor device 1 can be further increased.
- the step of adjusting the hydrogen atom concentration is performed by applying a gas containing hydrogen atoms to the substrate on which the insulating films (oxide films 8 and 26) are formed.
- a step of heat treatment using the atmospheric gas may be included.
- the hydrogen atom concentration in the vicinity of the interface between the semiconductor layer (p-type layer 4 including channel region, p region 23) and oxide films 8 and 26 can be easily adjusted.
- the step of adjusting the hydrogen atom concentration is performed after the step of performing heat treatment using a gas containing hydrogen atoms as the atmospheric gas, A step of heat-treating the substrate using a gas may be included.
- the carrier mobility of the semiconductor device 1 can be further increased.
- the gas containing hydrogen atoms may be water vapor or water vapor-containing oxygen gas.
- the hydrogen annealing step (S70) can be performed relatively easily.
- a step of preparing a substrate 2 made of silicon carbide having an off angle of 50 ° to 65 ° with respect to the plane orientation ⁇ 0001 ⁇ substrate preparation step (S10 )).
- a step of forming a semiconductor layer on the substrate 2 is performed.
- a step of forming an insulating film so as to be in contact with the surface of the semiconductor layer is performed.
- the semiconductor device 1 with increased carrier mobility (channel mobility) according to the present invention can be easily manufactured.
- a semiconductor device having the structure shown in FIG. 1 was fabricated as a sample as follows. That is, an epitaxial layer 3 having a thickness of 10 ⁇ m was formed on an n-type silicon carbide substrate 2 having a thickness of 400 ⁇ m, and a p-type layer 4 having a thickness of 1 ⁇ m was formed on the epitaxial layer 3. Then, phosphorus (P) was implanted as an n-type conductive impurity in the n + regions 5 and 6, and a value of 1 ⁇ 10 20 cm ⁇ 3 was used as the impurity concentration.
- the gate length (channel length L g ), which is the distance between the n + regions 5 and 6, was set to 100 ⁇ m.
- the gate width (channel width) was 200 ⁇ m.
- Example 1 of the present invention a sample was formed by performing nitrogen annealing after forming an oxide film by dry oxidation treatment.
- Example 2 of the present invention a sample was formed by performing an annealing process (argon annealing process) using nitrogen gas as an inert gas atmosphere after forming an oxide film and then performing nitrogen annealing. did.
- the heating temperature was 1200 ° C. and the heating time was 30 minutes.
- nitrogen monoxide gas was used as the atmosphere gas, the heating temperature was 1100 ° C., and the heating time was 60 minutes.
- nitrogen monoxide gas was used as the atmosphere gas, the heating temperature was 1100 ° C., and the heating time was 120 minutes.
- argon gas was used as atmospheric gas, the conditions of heating temperature 1100 degreeC and heating time 60 minutes were used.
- a sample that was not subjected to the nitrogen annealing step after the gate insulating film was formed was prepared as a sample for comparison.
- the thickness of the oxide film of Example 1 described above was 40 nm
- the thickness of the oxide film of Example 2 was 46 nm
- the thickness of the oxide film of the comparative example was 33 nm.
- a gate electrode 10 was formed thereon.
- the material of the source electrode 11 and the drain electrode 12 was nickel (Ni), and the thickness thereof was 0.1 ⁇ m.
- the gate electrode 10 is made of aluminum (Al) and has a thickness of 1 ⁇ m.
- the distribution in the depth direction of the nitrogen atom concentration in the interface vicinity of the oxide film 8 and the p-type layer 4 as a semiconductor layer was measured.
- a measuring method it measured by SIMS (secondary ion mass spectrometry).
- channel mobility was measured in the formed semiconductor device.
- the concentration distribution of nitrogen atoms in the depth direction is basically as shown in FIG.
- the horizontal direction indicates the depth from the surface of the oxide film, and the unit is nm.
- the vertical axis indicates the nitrogen atom concentration (unit: cm ⁇ 3 ).
- the nitrogen atom concentration is highest at the interface between the oxide film 8 and the p-type layer 4 as the semiconductor layer. It can be seen that the nitrogen atoms are distributed within a range of ⁇ 10 nm centering on the interface between the oxide film 8 and the p-type layer 4.
- FIG. 18 shows the measurement data for Example 1, but Example 2 also showed a substantially similar nitrogen atom concentration distribution. However, in Example 2, the maximum value (peak value) of the nitrogen atom concentration was higher than in Example 1.
- the horizontal axis in FIG. 19 represents the peak value of nitrogen atom concentration (nitrogen atom peak concentration) measured in each sample.
- the unit is cm ⁇ 3 .
- the vertical axis in FIG. 19 indicates the measured channel mobility (MOS channel mobility) of the semiconductor device.
- the unit is cm 2 / Vs.
- Example 19 in the sample of the comparative example, the peak concentration of nitrogen atoms was the lowest, and the value of the channel mobility was the lowest.
- the peak concentration of nitrogen atoms was higher than that of the sample of Comparative Example, and at the same time, the value of channel mobility was also large.
- Example 1 and Example 2 are compared, the value of channel mobility is higher in Example 2 where the peak concentration of nitrogen atoms is higher than in Example 1.
- the minimum necessary value for the channel mobility is considered to be 50 cm 2 / Vs. For this reason, it is considered that a sufficient channel mobility value can be realized if the peak concentration of nitrogen atoms is set to 1 ⁇ 10 21 cm ⁇ 3 or more from FIG. .
- Example 2 Next, the relationship between the off angle of the substrate 2 and the channel mobility was confirmed. This will be specifically described below.
- sample A sample was manufactured using the same manufacturing method as the sample manufacturing method of Example 2 described above. Specifically, four types of samples as comparative examples and three types of samples as examples of the present invention were prepared using substrates having different main surface orientations. That is, as Comparative Example 1, a silicon carbide substrate (8 ° off substrate of (0001)) in which the plane angle of the main surface of the substrate is (0001) is 8 °, and Comparative Example 2 is used.
- Channel mobility was measured for each sample described above.
- the channel mobility measurement method was basically the same as the channel mobility measurement method in the first embodiment.
- the measurement results are shown in FIG.
- the horizontal axis in FIG. 20 indicates the off angle (unit: °) with respect to the plane orientation ⁇ 0001 ⁇ of the main surface of the substrate constituting each sample, and the vertical axis indicates the channel mobility (unit) in the same manner as the vertical axis in FIG. : Cm 2 / Vs).
- the value of channel mobility is higher than that of the comparative example. It turns out that it is improving greatly.
- Example 3 Next, the contents of an experiment conducted to confirm the effect when hydrogen atoms are contained in a region within 10 nm from the interface between the semiconductor layer and the insulating film will be described.
- a semiconductor device having the structure shown in FIG. 1 was fabricated as a sample as follows. That is, an epitaxial layer 3 having a thickness of 10 ⁇ m was formed on an n-type silicon carbide substrate 2 having a thickness of 400 ⁇ m, and a p-type layer 4 having a thickness of 1 ⁇ m was formed on the epitaxial layer 3. Then, phosphorus (P) was implanted as an n-type conductive impurity in the n + regions 5 and 6, and a value of 1 ⁇ 10 20 cm ⁇ 3 was used as the impurity concentration.
- the gate length (channel length L g ), which is the distance between the n + regions 5 and 6, was set to 100 ⁇ m.
- the gate width (channel width) was 200 ⁇ m.
- Example 1 of the present invention an oxide film was formed by dry oxidation treatment, and then a sample subjected to hydrogen annealing was produced.
- Example 2 of the present invention a sample was formed by performing an annealing process (argon annealing process) using an argon gas as an atmosphere after performing hydrogen annealing after forming an oxide film. did.
- the heating temperature was 1200 ° C. and the heating time was 30 minutes.
- hydrogen gas was used as the atmosphere gas, the heating temperature was 1100 ° C., and the heating time was 60 minutes.
- Example 2 of the present invention hydrogen gas was used as the atmosphere gas for the hydrogen annealing conditions, the heating temperature was 1100 ° C., and the heating time was 120 minutes.
- argon gas was used as the atmosphere gas, the heating temperature was 1100 ° C., and the heating time was 60 minutes.
- a sample that was not subjected to the hydrogen annealing step after the gate insulating film was formed was prepared as a sample for comparison.
- the thickness of the oxide film of Example 1 mentioned above was 40 nm
- the thickness of the oxide film of Example 2 was 45 nm
- the thickness of the oxide film of the comparative example was 33 nm.
- a gate electrode 10 was formed thereon.
- the material of the source electrode 11 and the drain electrode 12 was nickel (Ni), and the thickness thereof was 0.1 ⁇ m.
- the gate electrode 10 is made of aluminum (Al) and has a thickness of 1 ⁇ m.
- the concentration distribution of hydrogen atoms in the depth direction was basically the same as the concentration distribution of nitrogen atoms shown in FIG. That is, similarly to the distribution of the nitrogen atom concentration shown in FIG. 18, the hydrogen atom concentration is highest at the interface between the oxide film 8 and the p-type layer 4 as the semiconductor layer, and the value is also 1 ⁇ 10 21 cm ⁇ . It was 3 or more.
- the hydrogen atoms were distributed within a range of ⁇ 10 nm around the interface between the oxide film 8 and the p-type layer 4. Note that both the samples of Example 1 and Example 2 described above showed substantially the same hydrogen atom concentration distribution. However, in the sample of Example 2, the maximum value (peak value) of the hydrogen atom concentration was higher than that of the sample of Example 1.
- the measurement result of the mobility in the channel also showed a similar relationship to the relationship between the peak value of the nitrogen atom concentration and the channel mobility shown in FIG.
- the minimum necessary value for the channel mobility is considered to be 50 cm 2 / Vs. For this reason, even if process variations are taken into account, as in the case of the peak concentration of nitrogen atoms, if the peak concentration of hydrogen atoms is 1 ⁇ 10 21 cm ⁇ 3 or more, a sufficient channel mobility value can be obtained. It can be realized.
- Example 4 Next, the contents of an experiment in which water vapor is used as an atmosphere gas for heat treatment and hydrogen atoms are contained in a region within 10 nm from the interface between the semiconductor layer and the insulating film will be described.
- a semiconductor device having the structure shown in FIG. 1 was manufactured as a sample.
- the sample preparation method is basically the same as the sample preparation method in Example 3 described above. That is, an epitaxial layer 3 having a thickness of 10 ⁇ m was formed on an n-type silicon carbide substrate 2 having a thickness of 400 ⁇ m, and a p-type layer 4 having a thickness of 1 ⁇ m was formed on the epitaxial layer 3. Then, phosphorus (P) was implanted as an n-type conductive impurity in the n + regions 5 and 6, and a value of 1 ⁇ 10 20 cm ⁇ 3 was used as the impurity concentration.
- the gate width (channel width) was 200 ⁇ m.
- Example 1 of the present invention a sample was formed by performing an oxygen gas annealing after forming an oxide film by dry oxidation treatment. Moreover, after forming an oxide film as a sample of Example 2 of the present invention, water vapor-containing oxygen gas annealing was performed, and further, annealing treatment using argon gas as an inert gas as an atmosphere (argon annealing treatment) was performed. A sample was prepared.
- the heating temperature was 1200 ° C. and the heating time was 30 minutes.
- a sample that was not subjected to the water vapor-containing oxygen gas annealing step after the gate insulating film was formed was prepared as a comparative sample.
- the thickness of the oxide film of Example 1 mentioned above was 40 nm
- the thickness of the oxide film of Example 2 was 44 nm
- the thickness of the oxide film of the comparative example was 33 nm.
- a gate electrode 10 was formed thereon.
- the material of the source electrode 11 and the drain electrode 12 was nickel (Ni), and the thickness thereof was 0.1 ⁇ m.
- the gate electrode 10 is made of aluminum (Al) and has a thickness of 1 ⁇ m.
- the concentration distribution of hydrogen atoms in the depth direction was basically the same as the concentration distribution of nitrogen atoms shown in FIG. 18, as in the case of the test of Example 3. That is, similarly to the distribution of the nitrogen atom concentration shown in FIG. 18, the hydrogen atom concentration is highest at the interface between the oxide film 8 and the p-type layer 4 as the semiconductor layer, and the value is also 1 ⁇ 10 21 cm ⁇ . It was 3 or more.
- the hydrogen atoms were distributed within a range of ⁇ 10 nm around the interface between the oxide film 8 and the p-type layer 4. Note that both the samples of Example 1 and Example 2 described above showed substantially the same hydrogen atom concentration distribution. However, in the sample of Example 2, the maximum value (peak value) of the hydrogen atom concentration was higher than that of the sample of Example 1.
- the measurement result of the mobility in the channel also showed a similar relationship to the relationship between the peak value of the nitrogen atom concentration and the channel mobility shown in FIG.
- the minimum necessary value for the channel mobility is considered to be 50 cm 2 / Vs. For this reason, even if process variations are taken into account, as in the case of the peak concentration of nitrogen atoms, if the peak concentration of hydrogen atoms is 1 ⁇ 10 21 cm ⁇ 3 or more, a sufficient channel mobility value can be obtained. It can be realized.
- Example 5 Next, the contents of the experiment in which nitrogen atoms and hydrogen atoms are contained in a region within 10 nm from the interface between the semiconductor layer and the insulating film using a gas containing nitrogen atoms and hydrogen atoms as the atmosphere gas for heat treatment will be described. .
- a semiconductor device having the structure shown in FIG. 1 was manufactured as a sample.
- the sample preparation method is basically the same as the sample preparation method in Example 3 described above. That is, an epitaxial layer 3 having a thickness of 10 ⁇ m was formed on an n-type silicon carbide substrate 2 having a thickness of 400 ⁇ m, and a p-type layer 4 having a thickness of 1 ⁇ m was formed on the epitaxial layer 3. Then, phosphorus (P) was implanted as an n-type conductive impurity in the n + regions 5 and 6, and a value of 1 ⁇ 10 20 cm ⁇ 3 was used as the impurity concentration.
- the gate width (channel width) was 200 ⁇ m.
- a sample was formed by performing nitrogen annealing after forming an oxide film by dry oxidation treatment. Further, as a sample of Example 1 of the present invention, after forming an oxide film, a nitrogen anneal was performed, and a sample was further subjected to a hydrogen anneal. Further, as a sample of Example 2 of the present invention, after forming an oxide film, a sample subjected to nitrogen annealing under a condition different from that of the sample of the reference example was prepared.
- Example 3 of the present invention after forming an oxide film, nitrogen annealing was performed under conditions different from those of Example 1 above, and a sample was further subjected to hydrogen annealing.
- the heating temperature was 1200 ° C. and the heating time was 30 minutes.
- nitrogen monoxide (NO) gas was used as the atmosphere gas, the heating temperature was 1100 ° C., and the heating time was 20 minutes.
- Example 1 of the present invention As the conditions for the nitrogen annealing step, nitrogen monoxide gas was used as the atmosphere gas, the heating temperature was 1100 ° C., and the heating time was 20 minutes. Moreover, about the hydrogen annealing process in the sample of Example 1, hydrogen gas was used for atmospheric gas, heating temperature was 1100 degreeC and heating time was 30 minutes. Further, in the nitrogen annealing step for the sample of Example 2, nitrogen monoxide (NO) gas was used as the atmosphere gas, the heating temperature was 1100 ° C., and the heating time was 60 minutes.
- NO nitrogen monoxide
- Example 3 of the present invention As the conditions for the nitrogen annealing step, a nitric oxide gas was used as the atmosphere gas, the heating temperature was 1100 ° C., and the heating time was 60 minutes. Moreover, about the hydrogen annealing process in the sample of Example 3, hydrogen gas was used for atmospheric gas, heating temperature was 1100 degreeC and heating time was 30 minutes.
- the thickness of the oxide film of the reference example described above is 41 nm
- the thickness of the oxide film of Example 1 is 45 nm
- the thickness of the oxide film of Example 2 is 41 nm
- the thickness of the oxide film of Example 3 is 45 nm
- the thickness of the oxide film was 33 nm.
- each sample is used as the source electrode 11 and the drain electrode 12 as shown in FIG.
- a gate electrode 10 was formed on the oxide film 8.
- the material of the source electrode 11 and the drain electrode 12 was nickel (Ni), and the thickness thereof was 0.1 ⁇ m.
- the gate electrode 10 is made of aluminum (Al) and has a thickness of 1 ⁇ m.
- the depth of the total concentration of nitrogen atoms and hydrogen atoms in the vicinity of the interface between the oxide film 8 and the p-type layer 4 as the semiconductor layer is measured by the same method as the measurement method in the test of Example 1 already described.
- the distribution in the vertical direction was measured. That is, SIMS (secondary ion mass spectrometry) was used as a measurement method.
- channel mobility was measured in the formed semiconductor device. As a measuring method, the same method as the measuring method in the test of Example 1 was used.
- the total concentration distribution of nitrogen atoms and hydrogen atoms in the depth direction was basically the same as the concentration distribution of nitrogen atoms shown in FIG. That is, similar to the distribution of nitrogen atom concentration shown in FIG. 18, the total concentration of nitrogen atoms and hydrogen atoms was highest at the interface between the oxide film 8 and the p-type layer 4 as the semiconductor layer.
- the nitrogen atoms and hydrogen atoms were distributed within a range of ⁇ 10 nm around the interface between the oxide film 8 and the p-type layer 4.
- the peak value (maximum value) of the nitrogen atom concentration in the sample of the reference example described above was 7 ⁇ 10 20 cm ⁇ 3 . Further, the peak value of the nitrogen atom concentration in the sample of Example 1 was 7 ⁇ 10 20 cm ⁇ 3 , and the peak value (maximum value) of the hydrogen atom concentration was 7 ⁇ 10 20 cm ⁇ 3 . Moreover, the positions of the concentration peaks of nitrogen atoms and hydrogen atoms overlapped. That is, the peak value of the total concentration of nitrogen atoms and hydrogen atoms in the sample of Example 1 was 1.4 ⁇ 10 21 cm ⁇ 3 .
- the peak value (maximum value) of the nitrogen atom concentration in the sample of Example 2 described above was 2 ⁇ 10 21 cm ⁇ 3 .
- the peak value of the nitrogen atom concentration in the sample of Example 3 was 2 ⁇ 10 21 cm ⁇ 3
- the peak value (maximum value) of the hydrogen atom concentration was 1 ⁇ 10 21 cm ⁇ 3 .
- the positions of the concentration peaks of nitrogen atoms and hydrogen atoms overlapped. That is, the peak value of the total concentration of nitrogen atoms and hydrogen atoms in the sample of Example 3 was 3 ⁇ 10 21 cm ⁇ 3 .
- the measurement result of the mobility in the channel also showed a relationship similar to the relationship between the peak value of the nitrogen atom concentration and the channel mobility shown in FIG.
- the measurement result of the mobility in the channel is shown in FIG.
- the horizontal axis in FIG. 21 indicates the peak value (peak concentration) of the total concentration of nitrogen atoms and hydrogen atoms measured in each sample.
- the unit is cm ⁇ 3 .
- the vertical axis in FIG. 21 indicates the measured channel mobility (MOS channel mobility) of the semiconductor device.
- the unit is cm 2 / Vs.
- the peak concentration of nitrogen atoms was the lowest and the value of the channel mobility was the lowest.
- the peak value of the total concentration of nitrogen atoms and hydrogen atoms was higher than that of the sample of Comparative Example, and at the same time, the value of channel mobility was also large.
- the sample having a larger peak value (peak concentration) of the total concentration of nitrogen atoms and hydrogen atoms has a larger channel mobility value. Yes.
- the minimum value necessary for channel mobility is considered to be 50 cm 2 / Vs as described above.
- the peak value (peak concentration) of the total concentration of nitrogen atoms and hydrogen atoms is 1 ⁇ 10 21 cm ⁇ 3 or more, as in the case of the peak concentration of nitrogen atoms.
- Example 6 In order to confirm the effect of the present invention, a semiconductor device was prototyped and the interface state of the interface between the semiconductor layer and the insulating film of the semiconductor device was evaluated.
- the semiconductor device shown in FIG. 22 is a MOS capacitor, which is an n-type silicon carbide substrate 2, a buffer layer 21 formed on the substrate 2, and a breakdown voltage holding layer 22 formed on the buffer layer 21. And the oxide film 26 formed on the breakdown voltage holding layer 22, the gate electrode 10 formed on the oxide film, and the back surface of the substrate 2 (the back surface opposite to the surface on which the buffer layer 21 is formed).
- the back electrode 31 is provided.
- the semiconductor device was manufactured by the following process. That is, the buffer layer 21 made of an n-type silicon carbide epitaxial layer was formed on the surface of the substrate 2 made of n-type silicon carbide having a thickness of 400 ⁇ m. The specific resistance of the substrate 2 is 0.02 ⁇ ⁇ cm.
- the buffer layer 21 had a thickness of 0.5 ⁇ m and an n-type impurity concentration of 5 ⁇ 10 17 cm ⁇ 3 .
- an n-type silicon carbide epitaxial layer 3 having a thickness of 10 ⁇ m was formed on the buffer layer 21, thereby forming a pressure resistant holding layer 22.
- the n-type impurity concentration of the breakdown voltage holding layer 22 was 5 ⁇ 10 15 cm ⁇ 3 .
- the heating temperature was 1200 ° C. and the heating time was 30 minutes.
- nitrogen monoxide (NO) gas was used as the atmosphere gas, the heating temperature was 1100 ° C., and the heating time was 60 minutes.
- a sample that was not subjected to the nitrogen annealing step after the oxide film 26 was formed was prepared as a sample for the comparative example. Note that the thickness of the oxide film 26 of the above-described embodiment was 40 nm, and the thickness of the oxide film 26 of the comparative example was 33 nm.
- the back electrode 31 as an ohmic electrode is formed on the back surface of the substrate 2 as shown in FIG. 22, and the gate is formed on the oxide film 26 as a gate insulating film.
- An electrode 10 was formed.
- the material constituting the back electrode 31 was nickel (Ni), and its thickness was 0.1 ⁇ m.
- the back electrode 31 was subjected to an alloying process (heat treatment) in a argon (Ar) atmosphere with a heating temperature of 950 ° C. and a heating time of 2 minutes.
- the material which comprises the gate electrode 10 was aluminum (Al), and the thickness was 1 micrometer.
- the planar shape of the gate electrode 10 is circular, and its diameter is 800 ⁇ m.
- Capacitance-voltage characteristics were measured for the samples of the above examples and comparative examples having the configuration of the semiconductor device (MOS capacitor) shown in FIG.
- the measurement frequency was 1 MHz.
- the low frequency CV measurement was performed by the quasistatic CV measurement method.
- the capacitance Cs due to the depletion layer formed on the semiconductor side of the MOS interface was obtained by solving the Poisson equation. At this time, a deep depletion state was assumed without considering the inversion state.
- the interface state density was calculated using the High-Low method for the samples of the above Examples and Comparative Examples.
- the outline of a method for calculating the interface state density using the High-Low method will be described below.
- the capacitance Cit due to the interface state having a relatively large emission time constant does not appear as a capacitance component.
- the CV measurement low frequency CV measurement
- the capacitance obtained by the low-frequency CV measurement includes information on oxide film capacitance, depletion layer capacitance, and interface state capacitance. Therefore, the capacitance C LF obtained by the low frequency CV measurement is
- the horizontal axis represents voltage
- the vertical axis represents capacity
- the capacitance is expressed by normalizing the entire capacitance C by the oxide film capacitance C ox .
- the comparative sample shown in FIG. 24 shows a relatively large difference between the high frequency CV characteristics and the low frequency CV characteristics. This is probably because the sample of the comparative example is more influenced by the capacity due to the interface state (interface state capacity) than the sample of the example.
- FIG. 25 shows the result of calculating the interface quasi-density for the samples of Examples and Comparative Examples by the above-described High-Low method.
- the vertical axis represents the interface state density
- the horizontal axis represents the energy value based on the conduction band.
- the sample of the example (with nitrogen annealing) has a lower interface state density than the sample of the comparative example (without nitrogen annealing) at any energy level. Further, even at an energy level 0.1 eV below the conduction band, the interface state density of the sample of the example is smaller than 1 ⁇ 10 12 cm ⁇ 2 eV ⁇ 1.
- Example 7 In order to confirm the effect of the present invention, a sample was prepared and the relationship between the interface state density and the MOS channel mobility was evaluated.
- a semiconductor device having the structure shown in FIG. 1 was fabricated as a sample as follows. That is, an epitaxial layer 3 having a thickness of 10 ⁇ m was formed on an n-type silicon carbide substrate 2 having a thickness of 400 ⁇ m, and a p-type layer 4 having a thickness of 1 ⁇ m was formed on the epitaxial layer 3. Then, phosphorus (P) was implanted as an n-type conductive impurity in the n + regions 5 and 6, and a value of 1 ⁇ 10 20 cm ⁇ 3 was used as the impurity concentration.
- the gate length (channel length L g ), which is the distance between the n + regions 5 and 6, was set to 100 ⁇ m.
- the gate width (channel width) was 200 ⁇ m.
- Example 1 of the present invention a sample was formed by performing nitrogen annealing after forming an oxide film by dry oxidation treatment.
- Example 2 of the present invention a sample was formed by performing nitrogen annealing after forming an oxide film and further performing annealing (argon annealing) using an argon gas as an inert gas as an atmosphere. did.
- the heating temperature was 1200 ° C. and the heating time was 30 minutes.
- NO gas was used as the atmosphere gas, the heating temperature was 1100 ° C., and the heating time was 60 minutes.
- the conditions for the nitrogen annealing step were NO gas as the atmosphere gas, heating temperature of 1100 ° C., and heating time of 120 minutes.
- NO gas as the atmosphere gas
- heating temperature was 1100 ° C.
- heating time was 60 minutes.
- a sample that was not subjected to the hydrogen annealing step after the gate insulating film was formed was prepared as a sample for comparison.
- the thickness of the oxide film of Example 1 mentioned above was 40 nm
- the thickness of the oxide film of Example 2 was 46 nm
- the thickness of the oxide film of the comparative example was 33 nm.
- a gate electrode 10 was formed thereon.
- the material of the source electrode 11 and the drain electrode 12 was nickel (Ni), and the thickness thereof was 0.1 ⁇ m.
- the gate electrode 10 is made of aluminum (Al) and has a thickness of 1 ⁇ m.
- measuring method In the formed semiconductor device sample, channel mobility was measured. As a measuring method, the same method as the measuring method in the test of Example 1 was used.
- the interface state density is calculated by the same method as in the test of Example 6 (that is, using the High-Low method based on the data of the high-frequency CV characteristics and the low-frequency CV characteristics). did.
- the measurement results are shown in FIG.
- the horizontal axis in FIG. 26 indicates the value of the interface state density at an energy level 0.1 eV below the conduction band.
- the unit is cm ⁇ 2 eV ⁇ 1 .
- the vertical axis in FIG. 26 indicates the measured channel mobility (MOS channel mobility) of the semiconductor device.
- the unit is cm 2 / Vs.
- the channel mobility increases as the interface state density decreases.
- the minimum value necessary for channel mobility is considered to be 50 cm 2 / Vs as described above.
- the range of the interface state density where the channel mobility is 50 cm 2 / Vs can be regarded as a range of 7 ⁇ 10 11 cm ⁇ 2 eV ⁇ 1 or less.
- the interface state density (under 0.1 eV from the conduction band) is 1 ⁇ 10 12. It can be considered that sufficient channel mobility can be realized if it is smaller than cm ⁇ 2 eV ⁇ 1 .
- the present invention is advantageously applied to a silicon carbide semiconductor device formed by contacting an insulating film with a semiconductor layer made of silicon carbide, such as a MOSFET or a DiMOSFET.
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Abstract
Description
図1を参照して、本発明による半導体装置の実施の形態1を説明する。
図8を参照して、本発明による半導体装置の実施の形態2を説明する。
まず、図2に示した半導体装置の製造方法と同様に、基板準備工程(S10)を実施する。ここでは、本発明の実施の形態1における半導体装置の製造方法と同様に、(03-38)面が主表面となった炭化ケイ素からなる基板2(図9参照)を準備する。
図13を参照して、本発明による半導体装置の実施の形態3を説明する。
図14に示す半導体装置の製造方法は、基本的には図2に示した半導体装置の製造方法と同様であるが、図2における窒素アニール工程(S50)に変えて水素アニール工程(S70)が実施される点が異なっている。具体的には、図2に示した製造方法と同様に、基板準備工程(S10)、エピタキシャル層形成工程(S20)、注入工程(S30)、ゲート絶縁膜形成工程(S40)を実施する。その後、水素アニール工程(S70)を実施する。具体的には、雰囲気ガスとして水素ガス(H2)ガスを用い、熱処理を行なう。この熱処理の条件としては、たとえば加熱温度を1100℃、加熱時間を1時間とする条件を用いることができる。この結果、酸化膜7とp型層4およびn+領域5、6との界面領域に水素原子を導入することができる。また、この水素アニール工程においては、上述した水素原子を含む雰囲気ガスを用いたアニール工程の後に、不活性ガスを用いたアニール工程、たとえばアルゴン(Ar)ガスを雰囲気ガスとして用いたアニール工程を実施してもよい。また、上述した水素アニール工程(S70)においては、水素ガスに代えて水蒸気もしくは水蒸気含有水素ガスを雰囲気ガスとして用いてもよい。
図15を参照して、本発明による半導体装置の実施の形態4を説明する。
図16に示す半導体装置の製造方法は、基本的には図2に示した半導体装置の製造方法と同様であるが、図16における窒素アニール工程(S50)の後であって電極形成工程(S60)の前に、水素アニール工程(S70)を行なっている点が異なっている。具体的には、図2に示した製造方法と同様に、基板準備工程(S10)、エピタキシャル層形成工程(S20)、注入工程(S30)、ゲート絶縁膜形成工程(S40)、窒素アニール工程(S50)を実施する。その後、水素アニール工程(S70)を実施する。この工程(S70)においては、実施の形態3の製造方法における水素アニール工程(S70)と同様の条件(水素ガスを用いたアニール条件)を用いることができる。この結果、酸化膜7とp型層4およびn+領域5、6との界面領域に窒素原子および水素原子を導入することができる。なお、上述した水素アニール工程(S70)においては、水素ガスに代えて水蒸気もしくは水蒸気含有酸素ガスを雰囲気ガスとして用いてもよい。また、水素アニール工程(S70)を、窒素アニール工程(S50)より先に実施してもよい。また、水素原子および窒素原子を含有する雰囲気ガスを用いる熱処理を実施することにより、水素アニール工程(S70)と窒素アニール工程(S50)とを同時に実施してもよい。
以下、本発明の効果を確認するために行なった実験の内容を説明する。
図1に示した構造の半導体装置を、試料として以下のように作製した。すなわち、厚みが400μmのn型炭化ケイ素基板2に、厚みが10μmのエピタキシャル層3を形成し、当該エピタキシャル層3上に厚みが1μmのp型層4を形成した。そして、n+領域5、6のn型の導電性不純物としてリン(P)を注入し、この不純物濃度として1×1020cm-3といった値を用いた。また、このn+領域5、6の間の距離であるゲート長(チャネル長Lg)を100μmとした。また、ゲート幅(チャネル幅)を200μmとした。
上述した各試料について、酸化膜8と半導体層としてのp型層4との界面近傍における窒素原子濃度の深さ方向での分布を測定した。測定方法としては、SIMS(二次イオン質量分析)により測定を行なった。また、形成された半導体装置において、チャネル移動度の測定を行なった。測定方法としては、以下のような方法を用いた。すなわち、ソース-ドレイン間電圧VDS=0.1Vとし、ゲート電圧VGを印加してソース-ドレイン間電流IDSを測定した(ゲート電圧依存性を測定した)。そして、gm=(δIDS)/(δVG)として、
チャネル移動度μ=gm×(L×d)/(W×ε×VDS)
(ここで、L:ゲート長、d:酸化膜厚、W:ゲート幅、ε:酸化膜の誘電率)
という式からチャネル移動度のゲート電圧に対する最大値を求めた。
深さ方向における窒素原子の濃度分布は、基本的には図18に示すような分布となった。図18において、横方向は酸化膜の表面からの深さを示し、単位はnmである。また、縦軸は窒素原子濃度(単位はcm-3)を示す。図18からわかるように、窒素原子濃度は酸化膜8と半導体層としてのp型層4との界面部において最も高くなっている。そして、当該窒素原子は、酸化膜8とp型層4との界面を中心として±10nmの範囲内に分布していることがわかる。なお、図18には実施例1についての測定データを示したが、実施例2についてもほぼ同様の窒素原子濃度分布を示した。ただし、実施例2では、窒素原子濃度の最大値(ピーク値)は実施例1よりも高くなっていた。
次に、基板2のオフ角度とチャネル移動度との関係を確認した。以下具体的に説明する。
上述した実施例2の試料の製造方法と同様の製造方法を用いて、試料を作製した。具体的には、用いる主表面の面方位が異なる基板を用いて、比較例としての試料を4種類、本発明の実施例としての試料を3種類作製した。すなわち、比較例1として、基板の主表面の面方位が(0001)のオフ角が8°となっている炭化ケイ素基板((0001)の8°オフ基板)を用いたもの、比較例2として基板の主表面の面方位が(01-15)で表わされる基板を用いたもの、比較例3として基板の主表面の面方位が(01-14)で表わされる基板を用いたもの、比較例4として、基板の主表面を表わす面方位が(0001)のオフ角が70°となっている基板を用いたものを準備した。また、本発明の実施例としては、実施例1として基板の主表面の面方位が(01-13)で表わされる基板を用いたもの、実施例2として基板の主表面の面方位が(03-38)で表わされる基板を用いたもの、実施例3として基板の主表面の面方位が(01-12)で表わされる基板を用いたものを準備した。そして、これらの異なる基板を用いて、同様の構造の半導体装置を上述した試料として形成した。
上述した各試料について、チャネル移動度を測定した。チャネル移動度の測定方法は、基本的には実施例1におけるチャネル移動度の測定方法と同様の方法を用いた。
測定結果を図20に示す。図20における横軸は、各試料を構成する基板の主表面の、面方位{0001}に対するオフ角度(単位:°)を示し、縦軸は図19の縦軸と同様にチャネル移動度(単位:cm2/Vs)を示している。図20からもわかるように、本発明の実施例に対応するオフ角度(50°以上65°以下)の範囲の実施例1~3の試料においては、チャネル移動度の値が比較例に比べて大きく向上していることがわかる。
次に、水素原子を半導体層と絶縁膜との界面から10nm以内の領域に含有させた場合の効果を確認するため行なった実験の内容を説明する。
図1に示した構造の半導体装置を、試料として以下のように作製した。すなわち、厚みが400μmのn型炭化ケイ素基板2に、厚みが10μmのエピタキシャル層3を形成し、当該エピタキシャル層3上に厚みが1μmのp型層4を形成した。そして、n+領域5、6のn型の導電性不純物としてリン(P)を注入し、この不純物濃度として1×1020cm-3といった値を用いた。また、このn+領域5、6の間の距離であるゲート長(チャネル長Lg)を100μmとした。また、ゲート幅(チャネル幅)を200μmとした。
上述した各試料について、すでに述べた実施例1の試験における測定方法と同様の方法により、酸化膜8と半導体層としてのp型層4との界面近傍における水素原子濃度の深さ方向での分布を測定した。つまり、測定方法としては、SIMS(二次イオン質量分析)を用いた。また、形成された半導体装置において、チャネル移動度の測定を行なった。測定方法としては、実施例1の試験における測定方法と同様の方法を用いた。
深さ方向における水素原子の濃度分布は、基本的には図18に示した窒素原子の濃度分布と同様の分布となった。つまり、図18に示した窒素原子濃度の分布と同様に、水素原子濃度は酸化膜8と半導体層としてのp型層4との界面部において最も高くなり、その値も1×1021cm-3以上となっていた。そして、当該水素原子は、酸化膜8とp型層4との界面を中心として±10nmの範囲内に分布していた。なお、上述した実施例1および実施例2の両方の試料とも、ほぼ同様の水素原子濃度分布を示した。ただし、実施例2の試料では、水素原子濃度の最大値(ピーク値)は実施例1の試料よりも高くなっていた。
次に、熱処理の雰囲気ガスとして水蒸気を用いて、水素原子を半導体層と絶縁膜との界面から10nm以内の領域に含有させた実験の内容を説明する。
図1に示した構造の半導体装置を、試料として作製した。試料の作成方法は、基本的には上述した実施例3における試料の作成方法と同様である。すなわち、厚みが400μmのn型炭化ケイ素基板2に、厚みが10μmのエピタキシャル層3を形成し、当該エピタキシャル層3上に厚みが1μmのp型層4を形成した。そして、n+領域5、6のn型の導電性不純物としてリン(P)を注入し、この不純物濃度として1×1020cm-3といった値を用いた。また、このn+領域5、6の間の距離であるゲート長(チャネル長Lg)を100μmとした。また、ゲート幅(チャネル幅)を200μmとした。
上述した各試料について、すでに述べた実施例1の試験における測定方法と同様の方法により、酸化膜8と半導体層としてのp型層4との界面近傍における水素原子濃度の深さ方向での分布を測定した。つまり、測定方法としては、SIMS(二次イオン質量分析)を用いた。また、形成された半導体装置において、チャネル移動度の測定を行なった。測定方法としては、実施例1の試験における測定方法と同様の方法を用いた。
深さ方向における水素原子の濃度分布は、実施例3の試験の場合と同様に、基本的には図18に示した窒素原子の濃度分布と同様の分布となった。つまり、図18に示した窒素原子濃度の分布と同様に、水素原子濃度は酸化膜8と半導体層としてのp型層4との界面部において最も高くなり、その値も1×1021cm-3以上となっていた。そして、当該水素原子は、酸化膜8とp型層4との界面を中心として±10nmの範囲内に分布していた。なお、上述した実施例1および実施例2の両方の試料とも、ほぼ同様の水素原子濃度分布を示した。ただし、実施例2の試料では、水素原子濃度の最大値(ピーク値)は実施例1の試料よりも高くなっていた。
次に、熱処理の雰囲気ガスとして窒素原子および水素原子を含有するガスを用いて、窒素原子および水素原子を半導体層と絶縁膜との界面から10nm以内の領域に含有させた実験の内容を説明する。
図1に示した構造の半導体装置を、試料として作製した。試料の作成方法は、基本的には上述した実施例3における試料の作成方法と同様である。すなわち、厚みが400μmのn型炭化ケイ素基板2に、厚みが10μmのエピタキシャル層3を形成し、当該エピタキシャル層3上に厚みが1μmのp型層4を形成した。そして、n+領域5、6のn型の導電性不純物としてリン(P)を注入し、この不純物濃度として1×1020cm-3といった値を用いた。また、このn+領域5、6の間の距離であるゲート長(チャネル長Lg)を100μmとした。また、ゲート幅(チャネル幅)を200μmとした。
上述した各試料について、すでに述べた実施例1の試験における測定方法と同様の方法により、酸化膜8と半導体層としてのp型層4との界面近傍における窒素原子および水素原子の合計濃度の深さ方向での分布を測定した。つまり、測定方法としては、SIMS(二次イオン質量分析)を用いた。また、形成された半導体装置において、チャネル移動度の測定を行なった。測定方法としては、実施例1の試験における測定方法と同様の方法を用いた。
深さ方向における窒素原子および水素原子の合計濃度分布は、基本的には図18に示した窒素原子の濃度分布と同様の分布となった。つまり、図18に示した窒素原子濃度の分布と同様に、窒素原子および水素原子の合計濃度は酸化膜8と半導体層としてのp型層4との界面部において最も高くなっていた。そして、当該窒素原子および水素原子は、酸化膜8とp型層4との界面を中心として±10nmの範囲内に分布していた。
本発明の効果を確認するため、半導体装置を試作し、当該半導体装置の半導体層と絶縁膜との界面の界面準位を評価した。
図22に示した半導体装置はMOSキャパシタであって、n型炭化ケイ素基板である基板2と、当該基板2上に形成されたバッファ層21と、バッファ層21上に形成された耐圧保持層22と、耐圧保持層22上に形成された酸化膜26と、酸化膜上に形成されたゲート電極10と、基板2の裏面(バッファ層21が形成された表面と反対側の裏面)に形成された裏面電極31とを備える。
図22に示した半導体装置(MOSキャパシタ)の構成を備える上記実施例及び比較例の試料について、容量-電圧特性(CV特性)を測定した。なお、高周波CV測定は測定周波数を1MHzとした。また、低周波CV測定は、QuasistaticCV測定法により行なった。なお、MOS界面の半導体側に形成される空乏層による容量Csについては、ポアソン方程式を解くことにより求めた。このとき、反転状態は考慮せず、深い空乏状態を仮定した。
しかし、上述のように高周波CV測定では界面準位容量は応答しない(検出されない)ので、高周波CV測定により得られた容量CHFは、
したがって、上記数式(1)、(2)より、
(測定結果)
図23~図25を参照して、上記測定の結果を説明する。
本発明の効果を確認するため、試料を作成して界面準位密度とMOSチャネル移動度との関係を評価した。
図1に示した構造の半導体装置を、試料として以下のように作製した。すなわち、厚みが400μmのn型炭化ケイ素基板2に、厚みが10μmのエピタキシャル層3を形成し、当該エピタキシャル層3上に厚みが1μmのp型層4を形成した。そして、n+領域5、6のn型の導電性不純物としてリン(P)を注入し、この不純物濃度として1×1020cm-3といった値を用いた。また、このn+領域5、6の間の距離であるゲート長(チャネル長Lg)を100μmとした。また、ゲート幅(チャネル幅)を200μmとした。
形成された半導体装置の試料において、チャネル移動度の測定を行なった。測定方法としては、実施例1の試験における測定方法と同様の方法を用いた。
測定結果を図26に示す。図26の横軸は、伝導帯より0.1eV下のエネルギーレベルにおける界面準位密度の値を示している。単位はcm-2eV-1である。また、図26の縦軸は、測定した半導体装置のチャネル移動度(MOSチャネル移動度)を示している。単位はcm2/Vsである。
Claims (30)
- 面方位{0001}に対しオフ角が50°以上65°以下である、炭化ケイ素からなる基板(2)と、
前記基板(2)上に形成され、炭化ケイ素からなる半導体層(4、23)と、
前記半導体層(4、23)の表面に接触するように形成された絶縁膜(8、26)とを備え、
前記半導体層(4、23)と前記絶縁膜(8、26)との界面から10nm以内の領域における窒素原子濃度の最大値が1×1021cm-3以上である、炭化ケイ素半導体装置(1)。 - 前記半導体層(4、23)と前記絶縁膜(8、26)との界面から10nm以内の前記領域には水素原子が含有されている、請求の範囲第1項に記載の炭化ケイ素半導体装置(1)。
- 伝導帯より0.1eV下での界面準位密度が1×1012cm-2eV-1よりも小さいことを特徴とする、請求の範囲第1項に記載の炭化ケイ素半導体装置(1)。
- 前記基板(2)のオフ方位が<11-20>方向±5°以下の範囲である、請求の範囲第1項に記載の炭化ケイ素半導体装置(1)。
- 前記基板(2)のオフ方位が<01-10>方向±5°以下の範囲である、請求の範囲第1項に記載の炭化ケイ素半導体装置(1)。
- 前記基板(2)の主表面の面方位は、面方位{03-38}に対しオフ角が-3°以上+5°以下である、請求の範囲第5項に記載の炭化ケイ素半導体装置(1)。
- 面方位{0001}に対しオフ角が50°以上65°以下である、炭化ケイ素からなる基板(2)と、
前記基板(2)上に形成され、炭化ケイ素からなる半導体層(4、23)と、
前記半導体層(4、23)の表面に接触するように形成された絶縁膜(8、26)とを備え、
前記半導体層(4、23)と前記絶縁膜(8、26)との界面から10nm以内の領域における水素原子濃度の最大値が1×1021cm-3以上である、炭化ケイ素半導体装置(1)。 - 前記半導体層(4、23)と前記絶縁膜(8、26)との界面から10nm以内の前記領域には窒素原子が含有されている、請求の範囲第7項に記載の炭化ケイ素半導体装置(1)。
- 伝導帯より0.1eV下での界面準位密度が1×1012cm-2eV-1よりも小さいことを特徴とする、請求の範囲第7項に記載の炭化ケイ素半導体装置(1)。
- 前記基板(2)のオフ方位が<11-20>方向±5°以下の範囲である、請求の範囲第7項に記載の炭化ケイ素半導体装置(1)。
- 前記基板(2)のオフ方位が<01-10>方向±5°以下の範囲である、請求の範囲第7項に記載の炭化ケイ素半導体装置(1)。
- 前記基板(2)の主表面の面方位は、面方位{03-38}に対しオフ角が-3°以上+5°以下である、請求の範囲第11項に記載の炭化ケイ素半導体装置(1)。
- 面方位{0001}に対しオフ角が50°以上65°以下である、炭化ケイ素からなる基板(2)と、
前記基板(2)上に形成され、炭化ケイ素からなる半導体層(4、23)と、
前記半導体層(4、23)の表面に接触するように形成された絶縁膜(8、26)とを備え、
前記半導体層(4、23)と前記絶縁膜(8、26)との界面から10nm以内の領域における窒素原子および水素原子の合計濃度の最大値が1×1021cm-3以上である、炭化ケイ素半導体装置(1)。 - 伝導帯より0.1eV下での界面準位密度が1×1012cm-2eV-1よりも小さいことを特徴とする、請求の範囲第13項に記載の炭化ケイ素半導体装置(1)。
- 前記基板(2)のオフ方位が<11-20>方向±5°以下の範囲である、請求の範囲第13項に記載の炭化ケイ素半導体装置(1)。
- 前記基板(2)のオフ方位が<01-10>方向±5°以下の範囲である、請求の範囲第13項に記載の炭化ケイ素半導体装置(1)。
- 前記基板(2)の主表面の面方位は、面方位{03-38}に対しオフ角が-3°以上+5°以下である、請求の範囲第16項に記載の炭化ケイ素半導体装置(1)。
- 面方位{0001}に対しオフ角が50°以上65°以下である、炭化ケイ素からなる基板(2)を準備する工程(S10)と、
前記基板(2)上に半導体層(4、23)を形成する工程(S20)と、
前記半導体層(4、23)の表面に接触するように絶縁膜(8、26)を形成する工程(S40)と、
前記半導体層(4、23)と前記絶縁膜(8、26)との界面から10nm以内の領域における窒素原子濃度の最大値が1×1021cm-3以上となるように窒素原子濃度を調整する工程(S50)とを備える、炭化ケイ素半導体装置の製造方法。 - 前記半導体層(4、23)と前記絶縁膜(8、26)との界面から10nm以内の前記領域に水素原子を含有させる工程(S70)をさらに備える、請求項18に記載の炭化ケイ素半導体装置の製造方法。
- 前記水素原子を含有させる工程は、前記絶縁膜(8、26)が形成された前記基板(2)を、水素原子を含有するガスを雰囲気ガスとして用いて熱処理する工程を含む、請求の範囲第19項に記載の炭化ケイ素半導体装置の製造方法。
- 前記水素原子を含有するガスは水蒸気または水蒸気含有酸素である、請求の範囲第20項に記載の炭化ケイ素半導体装置の製造方法。
- 前記窒素原子濃度を調整する工程(S50)は、前記絶縁膜(8、26)が形成された前記基板(2)を、窒素原子を含有するガスを雰囲気ガスとして用いて熱処理する工程を含む、請求の範囲第18項に記載の炭化ケイ素半導体装置の製造方法。
- 前記窒素原子濃度を調整する工程(S50)は、前記窒素原子を含有するガスを雰囲気ガスとして用いて熱処理する工程の後、不活性ガスを雰囲気ガスとして用いて前記基板を熱処理する工程を含む、請求の範囲第22項に記載の炭化ケイ素半導体装置の製造方法。
- 面方位{0001}に対しオフ角が50°以上65°以下である、炭化ケイ素からなる基板(2)を準備する工程(S10)と、
前記基板(2)上に半導体層(4、23)を形成する工程(S20)と、
前記半導体層(4、23)の表面に接触するように絶縁膜(8、26)を形成する工程(S40)と、
前記半導体層(4、23)と前記絶縁膜(8、26)との界面から10nm以内の領域における水素原子濃度の最大値が1×1021cm-3以上となるように水素原子濃度を調整する工程(S70)とを備える、炭化ケイ素半導体装置の製造方法。 - 前記半導体層(4、23)と前記絶縁膜(8、26)との界面から10nm以内の前記領域に窒素原子を含有させる工程(S50)をさらに備える、請求の範囲第24項に記載の炭化ケイ素半導体装置の製造方法。
- 前記窒素原子を含有させる工程(S50)は、前記絶縁膜(8、26)が形成された前記基板(2)を、窒素原子を含有するガスを雰囲気ガスとして用いて熱処理する工程を含む、請求の範囲第25項に記載の炭化ケイ素半導体装置の製造方法。
- 前記水素原子濃度を調整する工程(S70)は、前記絶縁膜(8、26)が形成された前記基板(2)を、水素原子を含有するガスを雰囲気ガスとして用いて熱処理する工程を含む、請求の範囲第24項に記載の炭化ケイ素半導体装置の製造方法。
- 前記水素原子濃度を調整する工程(S70)は、前記水素原子を含有するガスを雰囲気ガスとして用いて熱処理する工程の後、不活性ガスを雰囲気ガスとして用いて前記基板(2)を熱処理する工程を含む、請求の範囲第27項に記載の炭化ケイ素半導体装置の製造方法。
- 前記水素原子を含有するガスは水蒸気または水蒸気含有酸素である、請求の範囲第28項に記載の炭化ケイ素半導体装置の製造方法。
- 面方位{0001}に対しオフ角が50°以上65°以下である、炭化ケイ素からなる基板(2)を準備する工程(S10)と、
前記基板(2)上に半導体層(4、23)を形成する工程(S20)と、
前記半導体層(4、23)の表面に接触するように絶縁膜(8、26)を形成する工程(S40)と、
前記半導体層(4、23)と前記絶縁膜(8、26)との界面から10nm以内の領域における窒素原子および水素原子の合計濃度の最大値が1×1021cm-3以上となるように前記合計濃度を調整する工程(S50、S70)とを備える、炭化ケイ素半導体装置の製造方法。
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CN200980146557.3A CN102224594B (zh) | 2008-11-20 | 2009-02-03 | 碳化硅半导体器件及其制造方法 |
KR1020117007375A KR101225332B1 (ko) | 2008-11-20 | 2009-02-03 | 탄화규소 반도체 장치 및 그 제조 방법 |
US13/063,083 US8686434B2 (en) | 2007-12-04 | 2009-02-03 | Silicon carbide semiconductor device and method for manufacturing the same |
US14/179,371 US20140159057A1 (en) | 2008-11-20 | 2014-02-12 | Silicon carbide semiconductor device and method for manufacturing the same |
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US20110186862A1 (en) | 2011-08-04 |
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US8686434B2 (en) | 2014-04-01 |
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