JPH0864802A - Silicon carbide semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE: To provide an SiC semiconductor device, which has an electrode with small contact resistance against silicon carbide, and its manufacture and suppress reaction between the gate electrode material and the electrode wiring. CONSTITUTION: On the n-type source area 12 and the drain area 13 of a p-type SiC substrate 11, metal nitride electrodes 16a and 16b formed of TiN or ZrN or HfN or VN or TaN are formed. On the surface layer of the areas 12 and 13 whereupon the metal nitride electrodes 16a and 16b make contact, nitrogen rich layers 12a and 13a are formed. These nitrogen rich layers reduce contact resistance of the electrodes. A metal nitride layer 16c formed of TiN, ZrN or HfN or VN or TaN is provided between an Mo gate electrode 15 and Al electrode wiring 17c, and reaction between the electrode 15 and the electrode wiring 17c is suppressed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a MOSFET (Metal Oxide Semiconductor Field-Ef) using a silicon carbide substrate.
fect transistor), MESFET (MEtal Semiconduct)
or field-effect transistor), a bipolar transistor, a vertical MOS transistor, and other semiconductor devices, and a method for manufacturing the same. More specifically, it relates to a silicon carbide semiconductor device using a metal nitride as a contact electrode and a method for manufacturing the same.

[0002]

2. Description of the Related Art Silicon carbide (SiC) semiconductors are widely used at present in silicon (Si) and gallium arsenide (GaA).
The bandgap is wider than other semiconductors (2.2)
3.3 eV), it is also thermally, chemically and mechanically stable and has excellent radiation resistance. Therefore, a semiconductor device using silicon carbide can be used as an element showing high reliability and stability under severe conditions such as high temperature, large power, and radiation irradiation, which are difficult to use with other semiconductor materials, Applications in various fields are expected. In particular, the use as a light emitting device that emits blue light, which focuses on a wide band gap, is currently in the stage of practical application.

However, the application of silicon carbide as an electronic device is far behind that of its application as a light emitting element. One of the causes is that an electrode material suitable for a complicated electronic device manufacturing process, which forms an electrically favorable resistive contact with silicon carbide, and a forming method thereof have not been developed. At the research level, tungsten (W), which has been studied as an electrode material for forming a resistive contact to an n-type silicon carbide semiconductor,
There are titanium (Ti), nickel (Ni) and their silicides. These contact resistance values are roughly 1
It is about 0 ⁻¹ to 10 ⁻⁴ ohm · cm ² . This is far from the typical value (about 10 ⁻⁶ ohm · cm ² ) of a practically used Si or GaAs semiconductor device.

Further, W, Ti and their silicides deteriorate contact characteristics when heat-treated at a low temperature. At present, even Ni, which has a low contact resistance value, requires high temperature heat treatment at 1100 ° C. or higher to obtain a low contact resistance value. Thus, the above electrode material is not suitable for the device manufacturing process. TiN is disclosed as an electrode material for n-type silicon carbide resistive contact that does not require high temperature heat treatment (RCGlass et al., "Low").
energy ion-assisted deposition of titaniumnitride
ohmic contacts on alpha (6H) -silicon carbide "App
L. Phys. Lett. 59 (22), pp. 2868-2870 (1991)). According to this document, the TiN film is formed by a Ti vapor deposition method in which nitrogen ions are assisted by an ion gun.

On the other hand, as a conventional semiconductor device using a silicon carbide substrate, a MOSFET has been disclosed in, for example, JP-A-60-14.
It is disclosed in Japanese Patent No. 2568. This semiconductor device
After forming the source / drain regions on the p-type silicon carbide single crystal substrate, Ni is formed on the source / drain regions as these electrodes, and aluminum (A
l). Metal wiring is connected to these electrodes. Further, conventionally, in a semiconductor device of MESFET, platinum (Pt), gold (Au), and Al are used for the gate electrode.

[0006]

However, the TiN electrode formed by the Ti vapor deposition method assisted by nitrogen ions is
There is a drawback that the contact resistance is not low because nitrogen is not introduced into the surface layer portion of silicon carbide having a constant thickness which is in contact with the N electrode, or even if nitrogen is introduced, it is not electrically activated. In order to solve this point, n of silicon carbide
Attention has been focused on a method of electrically activating n-type carriers by introducing nitrogen, which is a type dopant, into silicon carbide, and as this method, a method of implanting nitrogen ions and then performing heat treatment has been attempted. However, according to this method, it is difficult to implant nitrogen ions into the surface layer portion of silicon carbide at a high concentration, so that there is a problem that particularly fine contacts cannot be easily formed. Further, the semiconductor device disclosed in JP-A-60-142568 has the following problems. That is, first, when Ni electrode material is used for the source / drain regions, the contact resistance is still higher than that of the semiconductor device of Si or GaAs as described above. Secondly, when Al is used as the gate electrode material, Al is melted by the high temperature heat treatment, so that a refractory metal such as molybdenum (Mo) or W must be actually used. When such a refractory metal is used, the refractory metal may be Al or tungsten silicide (WS
react with the electrode wire, such as i _x), uneven gate electrode, holes, a defect such as peeling was caused by the reaction product. Here, as a result of earnest study, the inventors of the present application
As a material for the electrode, a metal nitride made of titanium nitride (TiN), zirconium nitride (ZrN), hafnium nitride (HfN), vanadium nitride (VN) or tantalum nitride (TaN) is used, and a metal nitride layer is further used. It has been found that when a nitrogen (N) rich layer is formed on the surface layer portion of SiC in which is formed, the contact resistance becomes small. Further, by interposing between the WSi _x is a example Mo and the electrode wiring is a gate electrode material to the metal nitride layer, a gate electrode material is also finding can be suppressed from reacting with the electrode wiring.

An object of the present invention is to provide a silicon carbide semiconductor device having an electrode having a low contact resistance with respect to silicon carbide. Another object of the present invention is to provide a silicon carbide semiconductor device that suppresses the reaction between the gate electrode material and the electrode wiring. Still another object of the present invention is to provide a method for manufacturing these silicon carbide semiconductor devices.

[0008]

As shown in FIG. 1 or FIG. 7 (B), the invention according to claim 1 includes an n-type silicon carbide region 12, 13 or an n-type silicon carbide substrate 21. Metal nitride electrode 16a, 16b or 26a made of TiN, ZrN, HfN, VN or TaN formed on the silicon carbide regions 12 and 13 or the silicon carbide substrate 21.
26b, the nitrogen-rich layers 12a, 13a on the surface layer portion of the silicon carbide regions 12, 13 or the silicon carbide substrate 21 in contact with the metal nitride electrodes 16a, 16b or 26a, 26b. Or 22a, 23b
Is formed. As the n-type silicon carbide substrate 21 or the p-type silicon carbide substrate 11 for forming the n-type silicon carbide regions 12 and 13, either α-SiC or β-SiC may be used.

As shown in FIG. 1, the invention according to claim 2 is a silicon carbide semiconductor device in which a gate electrode 15 is provided on a p-type silicon carbide substrate 11 via an insulating film 14a. It is characterized in that a metal nitride layer 16c made of TiN, ZrN, HfN, VN or TaN is interposed between the electrode wiring 17c connected to the gate electrode 15. Gate electrode 1 according to claim 2
5 is made of Mo, W, a refractory metal such as silicide thereof, or polysilicon, and the electrode wiring 17c is Al or WS.
i _x .

As shown in FIG. 7B, the invention according to claim 3 is a silicon carbide semiconductor device in which a gate electrode 25 is directly provided on an n-type silicon carbide substrate 21, and the gate electrode 25 and this gate are provided. Electrode wiring 27 connected to the electrode 25
It is characterized in that a metal nitride layer 26c made of TiN, ZrN, HfN, VN or TaN is interposed between the metal nitride layer 26c and c. This semiconductor device is, for example, SiC-MES.
Applied to FET. The gate electrode 25 according to claim 3 is made of Au, Pt or Al, and the electrode wiring 27c is made of Al or WSi _x .

As shown in FIG. 1, the invention according to claim 4 is a p-type silicon carbide substrate 11, and this silicon carbide substrate 11
A gate electrode 15 provided on top of the insulating film 14a
And n-type source / drain silicon carbide regions 12 and 13 formed on the silicon carbide substrate 11, and TiN, ZrN, HfN, and V formed on the silicon carbide regions 12 and 13.
Metal Nitride Electrode 1 Made of N or TaN 1
A silicon carbide semiconductor device comprising: 6a, 16b,
TiN, ZrN, HfN, VN are provided between the gate electrode 15 and the electrode wiring 17c connected to the gate electrode 15.
Alternatively, a metal nitride layer 16c made of either TaN or TaN is interposed, and the metal nitride electrodes 16a, 1 are formed.
It is characterized in that nitrogen-rich layers 12a and 13a are formed on the surface layer portions of the silicon carbide regions 12 and 13 with which 6b is in contact.

According to a fifth aspect of the present invention, in the invention according to the fourth aspect, the gate electrode 15 is made of a refractory metal or polysilicon, and the p-type silicon carbide substrate 11 on both sides of the gate electrode 15 is n-type. Source / drain silicon carbide region 1
2, 13 are formed, and these silicon carbide regions 12, 13 are formed.
Is a silicon carbide semiconductor device in which electrodes 16a, 16b made of a metal nitride made of TiN, ZrN, HfN, VN or TaN are formed. This semiconductor device is applied to, for example, a SiC-MOSFET.

As shown in FIG. 7B, the invention according to claim 6 is an n-type silicon carbide substrate 21, and a gate electrode made of Au, Pt or Al directly provided on the silicon carbide substrate 21. 25, n-type source / drain silicon carbide regions 22 and 23 formed on the silicon carbide substrate 21, and TiN and Z formed on these silicon carbide regions 22 and 23.
A silicon carbide semiconductor device comprising electrodes 26a, 26b made of metal nitride made of any one of rN, HfN, VN, and TaN, comprising: the gate electrode 25; and an electrode wiring 27c connected to the gate electrode 25. Between TiN and Zr
Silicon carbide regions 22 and 2 in which a metal nitride layer 26c made of N, HfN, VN, or TaN is interposed and the metal nitride electrodes 26a and 26b are in contact with each other.
The nitrogen-rich layers 22a and 23b are formed in the surface layer portion of No. 3.

As shown in FIG. 1 or FIG. 7 (B), the invention according to claim 7 or 8 is the same as the invention according to claim 1, 4 or 6, and the nitrogen-rich layers 12a, 1
3a or 22a, 23a is 5 angstroms or more 50
Having a thickness of 0 angstroms or less and at least 1 ×
It contains nitrogen at a concentration of 10 ¹⁹ / cm ³ . The nitrogen-rich layers 12a, 13a or 22a, 23a preferably have a thickness of 20 angstroms or more and 500 angstroms or less and contain nitrogen at a concentration of at least 1 × 10 ²⁰ / cm ³ .

As shown in FIGS. 2A to 2I, the invention according to claim 9 is a step of forming n-type source / drain silicon carbide regions 12 and 13 on a p-type silicon carbide substrate 11. And a step of forming an insulating film 14a on the silicon carbide substrate 11 between the source / drain silicon carbide regions 12 and 13.
A step of forming a gate electrode 15 on the insulating film 14a, and a metal nitride layer 16c made of TiN, ZrN, HfN, VN or TaN on the gate electrode 15 and the source / drain silicon carbide regions 12 and 13. , 16
a and 16b respectively, and the electrode wirings 17c, 1 on the metal nitride layers 16c, 16a, 16b.
And a step of forming 7a and 17b.

The invention according to claim 10 is the metal nitride layer 1
Nitrogen-rich layers 12a, 13 are formed on the surface layer portions of the source / drain silicon carbide regions 12, 13 when forming 6a, 16b.
The method for manufacturing a silicon carbide semiconductor device according to claim 9, wherein a is formed, wherein the metal nitride layers 16c, 16a, 16b are formed in a nitrogen plasma atmosphere in a Ti, Zr, Hf, Metal target made of either V or Ta or TiN, ZrN, HfN, VN or T
The method for manufacturing a silicon carbide semiconductor device according to claim 9, wherein the method is performed by sputtering using a metal nitride target made of any of aN.

[0017]

According to the inventions of claims 1 and 10,
By forming the nitrogen-rich layers 12a, 13a or 22a, 23a in the silicon carbide region or the surface layer portion of the silicon carbide substrate, this nitrogen acts as a dopant and the contact resistance of the source / drain electrodes 16a, 16b or 26a, 26b is increased. Can be made smaller and these electrodes are made of SiC
It functions as a suitable electrode in a semiconductor device. According to the inventions of claims 2 and 3, the metal nitride layers 16c and 2 are provided between the gate electrodes 15 and 25 and the electrode wirings 17c and 27c.
By interposing 6c, the metal nitride layer 16
c and 26c act as a barrier metal layer, and the gate electrodes 15 and 25 and the electrode wirings 17c and 2 are also subjected to high temperature heat treatment.
Prevents reaction with 7c. Thereby, the gate electrode 1
No peeling occurs in No. 5, 25, and no problems such as unevenness occur. For example, the metal nitride layer functions as a reaction prevention layer between the refractory metal or polysilicon and the electrode wiring. Further, this metal nitride layer also functions as a diffusion preventing layer for impurities (P, B, As, etc.) doped in polysilicon to the outside in high temperature treatment.

According to the invention of claims 4, 5, and 6, the contact resistance of the electrodes 16a, 16b or 26a, 26b can be reduced by the nitrogen-rich layers 12a, 13a or 22a, 23a, and the metal nitride can be used. Layer 16c, 2
By interposing 6c, it is possible to completely eliminate defects such as peeling of the gate electrodes 15 and 25. According to the invention of claim 9, the contact resistance is small, and the electrodes 16a and 16b which are stable and do not react with SiC during the heat treatment in the manufacturing process are provided, and a defect such as peeling in the gate electrode 15 occurs. It is possible to easily manufacture a non-SiC semiconductor device with a small number of steps. According to the invention of claim 11, the nitrogen-rich layers 12a, 1
The nitrogen content of 3a can be made high.

In addition to the nitrogen plasma atmosphere during sputtering, a silicon carbide substrate having a thickness of 100 to 800 is used.
When the temperature is set to about 0 ° C, preferably 200 to 400 ° C, the surface layer portion is activated and the nitrogen content of the nitrogen-rich layer can be further increased. After forming the nitrogen-rich layer, when sputtering is further continued, the metal nitride is selectively formed in the activated nitrogen-rich layer to form the source electrode and the drain electrode. The interface between the metal nitride electrode and silicon carbide is not impaired even if the subsequent ambient temperature reaches about 900 ° C. due to the barrier property of the metal nitride, and the surface layer portion is also maintained. As a result, the electrical characteristics of the metal nitride electrode do not deteriorate even at high temperatures. Further, even if this electrode is not subjected to heat treatment after sputtering, that is, in a so-called "as deposited" state, since the contact resistance is small, no special heat treatment is required after sputtering.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. <Example 1> As shown in FIGS. 1 and 2, in this example, S
The iC-MOSFET silicon carbide semiconductor device 10 will be described. First, as shown in FIG. 2A, p-type SiC
An n-type source region 12 and an n-type drain region 13 are formed on a substrate 11 (hereinafter, referred to as p-SiC) by ion implantation at predetermined intervals. This SiC
An insulating film 14a made of SiO ₂ is formed on the surface of the SiC substrate 11 by thermally oxidizing the substrate 11, and then a Mo film is laminated as a gate electrode 15 on this insulating film 14a in this example. Next, as shown in FIG. 2B, an insulating film 14b made of SiO ₂ is formed on the insulating film 14a and the gate electrode 15 by a chemical vapor deposition (CVD) method, and then, as shown in FIG. ), A photoresist 14c is formed on the insulating film 14b in a predetermined pattern. As shown in FIG. 2D, the insulating films 14a and 14b not covered with the photoresist 14c are removed by etching with a hydrofluoric acid-based etchant. Thereby, the source / drain regions 12, 13 and the gate electrode 15
Is exposed.

Next, as shown in FIG. 2E, sputtering using a Ti target is performed in a nitrogen plasma atmosphere. Nitrogen-rich layers 12a and 13a are formed on the surface layers of the source / drain regions 12 and 13, and then T is formed on the entire surface including the nitrogen-rich layers 12a and 13a and the gate electrode 15.
The iN _x layer 16 is formed. SiC substrate 11 at this time
Is maintained at 200 to 400 ° C. This is because a suitable TiN _x layer cannot be formed when the substrate temperature is low. Then, as shown in FIG. 2 (F), WS is formed on the TiN _x layer 16.
After forming the i _x layer 17, as shown in FIG.
A photoresist 18 is formed on the i _x layer 17 in a predetermined pattern. As shown in FIG. 2H, only the WSi _x layer 17 is selectively etched by a hydrofluoric nitric acid-based etchant to partially expose the TiN _x layer 16. After masking only the last remaining WSi _x layer 17, the exposed TiN _{x layer}
Layer 16 is partially removed by wet etching using a mixed solution of hydrogen peroxide solution and sulfuric acid or dry etching using a fluorine-based gas to obtain silicon carbide semiconductor device 10 shown in FIGS. 2 (I) and 1.

[0022] In FIG. 1, 16a denotes a source electrode made of TiN _x, 16b drain electrode made of TiN _x,
16c is a TiN _x layer. W on the source electrode 16a
The electrode wiring 17a made of Si _x is formed on the gate electrode 15 via the TiN _x layer 16c and the electrode wiring 1 made of WSi _x 1
7c, and an electrode wiring 17b made of WSi _x is provided on the drain electrode 16b. Following the step shown in FIG. 2, an Al electrode (not shown) for fixing the potential of the SiC substrate 11 is formed on the p-SiC substrate 11. In order to secure the resistive contact between the p-SiC substrate 11 and the Al electrode, high temperature heat treatment at about 900 ° C. is performed. In this high temperature heat treatment, the TiN _x layer 16
c functions as a barrier metal that suppresses the reaction between the gate electrode 15 made of Mo and the electrode wiring 17c.

The nitrogen-rich layers 12a and 13a in the surface layer portions of the source / drain regions 12 and 13 are formed by doping nitrogen with plasma. Compared with the source / drain regions formed by ion implantation, the nitrogen-rich layers 12a and 13a are considerably shallower than the surface layer region, that is, the depth region of 500 angstroms or less from the surface.
Is formed. Further, in this plasma-assisted nitrogen doping, only the shallow outermost layer can be highly doped with nitrogen. When nitrogen is ion-implanted instead of plasma-assisted nitrogen doping, high-concentration doping cannot be performed only on the outermost surface layer. Therefore, the plasma-assisted nitrogen doping makes it possible to obtain good contact characteristics without substantially changing the sheet resistance value of the source / drain regions.

Example 2 In order to form the source electrode 16a and the drain electrode 16b made of TiN _{x on} the source region 12 and the drain region 13 of the SiC substrate 11 of Example 1, radio frequency (RF) sputtering is performed under the following conditions. went. At this time, the source region 12 and the drain region 13 each had a nitrogen concentration of 2 to 8 × 10 ¹⁸ / cm ³ .・ Target: Ti target ・ SiC substrate bias: None ・ SiC substrate temperature: 300 ° C. ・ RF power: 400 W ・ Nitrogen partial pressure: 0.5 Pa ・ TiN _x film: 1000 Å <Example 3> Nitrogen partial pressure of 2.0 Pa Under the same conditions as in Example 2, except that
RF sputtering was performed to form an electrode made of N _x .

After forming a 1000 Å thick TiN _x film on a SiC substrate, WSi _x 5000 was deposited on the TiN _x film to measure the contact resistance of the samples of Examples 2 and 3. It was formed to a thickness of angstrom. This WSi _x film is a protective film for preventing the TiN _x film from being damaged by the probe needle during contact measurement. After forming the WSi _x film, a predetermined electrode was formed and heat-treated at 400 ° C. for 1 hour in an argon atmosphere. The contact resistance value of the two samples after the heat treatment at room temperature was measured by the four-terminal cross bridge Kelvin method. The results are shown in Table 1.

[0026]

[Table 1]

On the other hand, the SiC substrates of Examples 2 and 3 immediately after the TiN _x film was formed under the above conditions were washed with a mixed solution of hydrogen peroxide and sulfuric acid to remove the TiN _x film and to remove secondary ions. Secondary Ion Mass Spectroscopy;
The concentration distribution of nitrogen from the SiC surface to the inside of the SiC was measured by SIMS). The results are shown in FIGS. 3 and 4.
For the sample of Example 3, room temperature (25 ° C.), 5
0 ° C, 100 ° C, 150 ° C, 200 ° C, 250 ° C, 30
Heat to 0 ℃, 350 ℃, 400 ℃ and 450 ℃ in sequence,
The contact resistance value was measured at each temperature. The result is shown in FIG. As is clear from Table 1, the contact resistance values of Example 2 and Example 3 were about one digit smaller than the conventional contact resistance value (10 ⁻⁴ ohm · cm ² ). Further, as is clear from FIGS. 3 and 4, in both the samples of Examples 2 and 3, nitrogen was introduced at a high concentration of 2 × 10 ¹⁹ / cm ³ over a depth of 200 Å from the SiC surface. Particularly, at a depth of about 5 angstroms from the SiC surface, the sample of Example 2 has a high concentration of 1 × 10 ²¹ / cm ³ and the sample of Example 3 has a high concentration of 1 × 10 ²⁰ / cm ^3. Was introduced. Furthermore, as is clear from FIG.
The contact resistance value of the electrode made of iN _x is 5.5 × 10 ⁻⁵ ohm · cm ² even when the temperature is changed from room temperature to 450 ° C.
To 5.0 × 10 ⁻⁵ ohm · cm ² only slightly. The contact resistance value showed a reversible change with temperature.

<Embodiment 4> FIG. 6 shows S of Embodiment 4 of the present invention.
The iC bipolar transistor and its manufacturing method are shown. Also in this embodiment, as in the case of the first embodiment, the TiN _x layer is formed between the electrode wiring and the electrode. In addition, TiN _x is used as an electrode for an n-type SiC (hereinafter referred to as n-SiC) substrate. Formation of TiN _x is performed in the same manner as in Example 1. Also, as the wiring on TiN _x , W
Using the Si _x or the like. As shown in FIG. 6 (A), this S
iC bipolar transistor is Si substrate, 4H-SiC
It is made by heteroepitaxially growing 3C-SiC (β-SiC) on either a (α-SiC) substrate or a 6H-SiC (α-SiC) substrate. Note that this transistor may be manufactured by homoepitaxially growing 4H-SiC or 6H-SiC on a 4H-SiC substrate or 6H-SiC substrate. Specifically, n− on the substrate
SiC, p-SiC, and n-SiC are grown in this order. Then, as shown in FIG. 6B, n-SiC and p-Si
Part of C is dry-etched using a fluorine-based gas,
Part of the upper surfaces of the lower two epitaxial layers, the p-SiC layer and the n-SiC layer thereabove are exposed. Further, as shown in FIG. 6C, A is formed on the p-SiC layer.
An electrode containing Al or Al such as Al-Si is formed.
Then, heat treatment is performed at a high temperature of 900 ° C. or higher. Figure 6
As shown in (D), a TiN _x film is formed by the same process as in the first embodiment. And Ti after this etching
Electrode wiring, such as WSi _x, is formed on the N _x layer. The WSi _x film may be continuously formed on the TiN _x film, and these may be simultaneously etched.

<Embodiment 5> FIG. 7 shows M of Embodiment 5 of the present invention.
The manufacturing method of the silicon carbide semiconductor device 20 of ESFET is shown. As shown in FIG. 7A, the same n-type Si as in Example 1 is used.
A gate electrode 25 of Au, Pt or Al is directly provided on the C substrate 21 by vapor deposition or sputtering. Figure 7
As shown in (B), the n-type source region 22 and the drain region 2 are formed in the silicon carbide substrate 21 on both sides of the gate electrode 25.
3 is formed. Perform sputtering Ti as a target in a nitrogen plasma atmosphere as in Example 1, the source electrode layer 26a made of each TiN _x on the source and drain regions 22, 23 and the gate electrode 25, the drain electrode 26b and the TiN _x layer 26c is formed.
At this time, the nitrogen-rich layers 22a, 2 are formed on the surface layers of the source / drain regions 22, 23 in contact with the electrode poles 26a, 26b.
3a is formed. Also in this example, TiN _x is used as a resistive contact electrode material to the SiC substrate. <Sixth Embodiment> FIG. 8 shows a sixth embodiment of the present invention. This is an example in which the present invention is applied to a so-called vertical MOS transistor. TiN for gate electrode and source region
_This is an example of forming _x . This vertical MOS transistor is manufactured as follows. First, n ⁺ -SiC substrate 3
An n-SiC layer 32 and a p-SiC layer 33 are formed on the surface of No. 1 by epitaxial growth in this order. Next, nitrogen is ion-implanted into these SiC layers 33 to form n ⁺ -SiC.
After the layer 34 is formed, it is annealed to repair the damage of the ion implantation. Next, reactive ion etching (Re
After the anisotropic dry etching of the SiC layer into a U shape by active-ion etching (RIE), an insulating film 35 made of SiO ₂ is formed. Then after forming the gate electrode 36 in a U-shaped portion, a contact hole is formed in the source region, the source electrode layer 37a made of TiN _x in the same manner as in Example 1 on the source region and the gate electrode 36 and the TiN _x
Form layer 37c. At this time, the nitrogen-rich layer 38 is formed in the surface layer portion of the source region in contact with the source electrode layer 37a. Further subsequently, the source electrode layer 37a and the TiN _x layer 3
The electrode wirings 39a and 39b made of WSi _x are formed on the 7c, and finally the drain electrode 40 is formed on the back surface of the SiC substrate 31.
To form.

Although TiN _x is exemplified as the metal nitride in the above Examples 1 to 6, TiN _x is used in Examples 1 to 6.
Instead of N _x , a metal nitride such as ZrN, HfN, VN, TaN may be used.

[0031]

As described above, according to the present invention, a source / drain electrode material having a low contact resistance can be obtained. Further, it is possible to form the gate electrode of the SiC semiconductor device in which defects such as peeling, unevenness and holes due to high temperature heat treatment do not occur. Further, it is possible to provide a method for manufacturing such a practicable SiC semiconductor device.

[Brief description of drawings]

FIG. 1 is a SiC-MOSFET according to a first embodiment of the present invention.
3 is a cross-sectional view showing the schematic structure of FIG.

FIG. 2 is a cross-sectional view for explaining the manufacturing process of the SiC-MOSFET.

FIG. 3 is a nitrogen concentration distribution diagram in a surface layer portion of a silicon carbide region of Example 2 of the present invention.

FIG. 4 is a nitrogen concentration distribution chart in a surface layer portion of a silicon carbide region of Example 3 of the present invention.

FIG. 5 is a graph showing the temperature dependence of the contact resistance value of the electrode made of TiN _{x of} Example 3 of the present invention.

FIG. 6 is a cross-sectional view for explaining the manufacturing process of the SiC bipolar transistor according to the fourth embodiment of the present invention.

FIG. 7 is a SiC-MESFET according to a fifth embodiment of the present invention.
FIG. 6 is a cross-sectional view for explaining the manufacturing process of.

FIG. 8 is a sectional view showing a vertical MOS transistor according to a sixth embodiment of the present invention.

[Explanation of symbols]

10, 20 Silicon carbide semiconductor device 11, 21 SiC (silicon carbide) substrate 12, 22 Source region (silicon carbide region) 13, 23 Drain region (silicon carbide region) 12a, 13a, 22a, 23a Nitrogen-rich layer 14a, 14b Insulation Films 15, 25 Gate electrodes 16, 16c, 26c TiN _x layers (metal nitride layers) 16a, 26a Source electrodes 16b, 26b Drain electrodes 17 WSi _x layers 17a, 17b, 17c, 27a, 27b, 27c Electrode wiring

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[Procedure amendment]

[Submission date] June 27, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008]

As shown in FIG. 1 or FIG. 7 (B), the invention according to claim 1 includes an n-type silicon carbide region 12, 13 or an n-type silicon carbide substrate 21. Metal nitride electrode 16a, 16b or 26a made of TiN, ZrN, HfN, VN or TaN formed on the silicon carbide regions 12 and 13 or the silicon carbide substrate 21.
26b, the nitrogen-rich layers 12a, 13a on the surface layer portion of the silicon carbide regions 12, 13 or the silicon carbide substrate 21 in contact with the metal nitride electrodes 16a, 16b or 26a, 26b. Or 22a, 23a
Is formed. As the n-type silicon carbide substrate 21 or the p-type silicon carbide substrate 11 for forming the n-type silicon carbide regions 12 and 13, either α-SiC or β-SiC may be used.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

As shown in FIG. 7B, the invention according to claim 6 is an n-type silicon carbide substrate 21, and a gate electrode made of Au, Pt or Al directly provided on the silicon carbide substrate 21. 25, n-type source / drain silicon carbide regions 22 and 23 formed on the silicon carbide substrate 21, and TiN and Z formed on these silicon carbide regions 22 and 23.
A silicon carbide semiconductor device comprising electrodes 26a, 26b made of metal nitride made of any one of rN, HfN, VN, and TaN, comprising: the gate electrode 25; and an electrode wiring 27c connected to the gate electrode 25. Between TiN and Zr
Silicon carbide regions 22 and 2 in which a metal nitride layer 26c made of N, HfN, VN, or TaN is interposed and the metal nitride electrodes 26a and 26b are in contact with each other.
Nitrogen-rich layers 22a and 23a are formed on the surface layer portion of No. 3.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location H01L 29/78 301 B (72) Inventor Toyama Noh, 1297 Kitabukuro-cho, Omiya City, Saitama Prefecture Mitsubishi Central Research Laboratory, Materials Co., Ltd.

Claims (11)

[Claims] 1. An n-type silicon carbide region (12, 13) or an n-type silicon carbide substrate (21), and TiN formed on the silicon carbide region (12, 13) or silicon carbide substrate (21). , ZrN, Hf
A silicon carbide semiconductor device comprising a metal nitride electrode (16a, 16b or 26a, 26b) made of N, VN or TaN, wherein the metal nitride electrode (16a, 16b or 26a) , 26b) are in contact with the silicon carbide region (12, 13) or a surface portion of the silicon carbide substrate (21) a nitrogen-rich layer (12a, 13a or 22a, 23b) is formed, a silicon carbide semiconductor characterized by apparatus. 2. An insulating film (14) is formed on a p-type silicon carbide substrate (11).
In a silicon carbide semiconductor device provided with a gate electrode (15) made of refractory metal or polysilicon via a), the gate electrode (15) and an electrode wiring (17c) connected to the gate electrode (15) Between TiN, ZrN, HfN, VN
A silicon carbide semiconductor device characterized in that a metal nitride layer (16c) made of either TaN or TaN is interposed. 3. Au, Pt on an n-type silicon carbide substrate (21)
Alternatively, in a silicon carbide semiconductor device in which the Al gate electrode (25) is directly provided, TiN, ZrN, HfN, between the gate electrode (25) and the electrode wiring (27c) connected to the gate electrode (25), VN
A silicon carbide semiconductor device characterized in that a metal nitride layer (26c) made of either TaN or TaN is interposed. 4. A p-type silicon carbide substrate (11), a gate electrode (15) provided on the silicon carbide substrate (11) via an insulating film (14a), and the silicon carbide substrate (11). N-type source / drain silicon carbide regions (12, 13) formed above, and TiN, ZrN, Hf formed on the silicon carbide regions (12, 13)
A silicon carbide semiconductor device comprising: a metal nitride electrode (16a, 16b) made of N, VN or TaN, the gate electrode (15) being connected to the gate electrode (15). TiN, ZrN, HfN, VN between electrode wiring (17c)
Or a metal nitride layer (16c) made of TaN is interposed, and the metal nitride electrodes (16a, 16b)
A silicon carbide semiconductor device, wherein a nitrogen-rich layer (12a, 13a) is formed on a surface layer portion of the silicon carbide region (12, 13) in contact with each other. 5. The gate electrode (15) is made of a refractory metal or polysilicon, and an n-type source / drain silicon carbide region is formed on the p-type silicon carbide substrate (11) on both sides of the gate electrode (15).
(12,13) are formed, and Ti is formed on the silicon carbide region (12,13).
The electrode (16a, 16b) made of a metal nitride made of any one of N, ZrN, HfN, VN and TaN is formed.
The silicon carbide semiconductor device described. 6. An n-type silicon carbide substrate (21), a gate electrode (25) made of Au, Pt or Al directly provided on the silicon carbide substrate (21), and the silicon carbide substrate (21). N-type source / drain silicon carbide regions (22, 23) formed in
TiN, Zr formed on the silicon carbide regions (22, 23)
A silicon carbide semiconductor device comprising a metal nitride electrode (26a, 26b) made of N, HfN, VN or TaN, the gate electrode being connected to the gate electrode (25) and the gate electrode (25). TiN, ZrN, HfN, VN between the electrode wiring (27c)
Or a metal nitride layer (26c) made of TaN is interposed and the metal nitride electrodes (26a, 26b)
A silicon carbide semiconductor device characterized in that a nitrogen-rich layer (22a, 23a) is formed on a surface layer portion of the silicon carbide region (22, 23) in contact with each other. 7. A metal nitride electrode (16a, 16b or 26a, 26)
b) a nitrogen-rich layer (12a, 13a) formed in the surface layer portion of the silicon carbide region (12, 13 or 22, 23) or the silicon carbide substrate (21) in contact with
Or 22a, 23a) has a thickness of at least 5 angstroms and contains nitrogen at a concentration of at least 1 × 10 ¹⁹ / cm ³ , silicon carbide semiconductor device according to any one of claims 1, 4 and 6. . 8. A metal nitride electrode (16a, 16b or 26a, 26)
b) a nitrogen-rich layer (12a, 13a) formed in the surface layer portion of the silicon carbide region (12, 13 or 22, 23) or the silicon carbide substrate (21) in contact with
Or 22a, 23a) has a thickness of at least 20 angstroms and contains nitrogen in a concentration of at least 1 × 10 ²⁰ / cm ³ . 9. A step of forming n-type source / drain silicon carbide regions (12, 13) on a p-type silicon carbide substrate (11), and carbonization between the source / drain silicon carbide regions (12, 13). Forming an insulating film (14a) on a silicon substrate (11); forming a gate electrode (15) on the insulating film (14a); forming the gate electrode (15) and a source / drain silicon carbide region;
TiN, ZrN, HfN, VN or TaN on (12,13)
A step of forming a metal nitride layer (16c, 16a, 16b) consisting of any of the above, electrode wiring (17c, 17a, on the metal nitride layer (16c, 16a, 16b) (17c, 17a,
17b) is formed, The manufacturing method of the silicon carbide semiconductor device characterized by the above-mentioned. 10. The nitrogen-rich layer (12a, 13a) is formed on the surface layer portion of the source / drain silicon carbide regions (12, 13) when the metal nitride layer (16a, 16b) is formed. Manufacturing method of silicon carbide semiconductor device. 11. Ti, Zr, H in a nitrogen plasma atmosphere
The metal nitride layer (16c, 16a, 16b) is formed by sputtering using a metal target made of f, V or Ta or a metal nitride target made of TiN, ZrN, HfN, VN or TaN. Claim 9
A method for manufacturing the described silicon carbide semiconductor device.