JP2003100658A - Electronic device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic device in which the contact resistance across an SiC semiconductor and an electrode is reduced. SOLUTION: The electronic device is provided with a p-type or n-type SiC semiconductor part and a carbon electrode which is installed on the SiC semiconductor part and which contains a carbon nanotube extended from the surface of the SiC semiconductor part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device and a manufacturing method thereof, and more particularly to an electronic device having a SiC semiconductor portion and a manufacturing method thereof.

[0002]

2. Description of the Related Art A SiC semiconductor has large physical properties such as a melting point, an energy bandgap, a dielectric breakdown electric field, a thermal conductivity, and a saturation speed as compared with other semiconductors which are commonly used at present (for example, Si). It is stable mechanically, chemically and mechanically and has excellent radiation resistance. Therefore, it is expected to realize an electronic device with ultra-low loss and capable of operating at high temperature using a SiC semiconductor.

In order to apply the above-mentioned SiC semiconductor to an electronic device, a low resistance ohmic contact forming technique is indispensable. For example, if a large contact resistance is parasitic on the current path of the device, power proportional to the product of the square of the current and the resistance is wasted as heat. Since this heat heats the device, it is also a cause of hindering the reduction and integration of the device. Further, since contact resistance decreases the switching speed of the device, it is important to reduce the contact resistance especially in high frequency applications.

As a method of forming an ohmic electrode on a SiC semiconductor, for example, for n-type SiC, Ni is used.
Alternatively, it is known that a Ni / Ti / W laminated film or the like is vapor-deposited on the SiC surface and then subjected to a high temperature alloying treatment at 900 ° C to 1100 ° C. On the other hand, for p-type SiC, A
It is known that a high temperature alloying process is performed after vapor deposition of 1 or Al / Ti, an Al-Ti alloy or the like on the SiC surface.

However, in the above method, n-type ρc
= 1 × 10 ⁻⁵ Ωcm ² , p-type ρc = 1 × 10 ⁻⁴ Ω
Only a contact resistance of about cm ² has been achieved. With respect to the n-type electrode, when SiC and Ni react with each other to generate nickel silicide, excess C remains on the ohmic interface, and a void is generated. Is believed to be diffused in SiC and cause a spike phenomenon. On the other hand, regarding the p-type, it is considered that the natural oxide film existing on the SiC surface or the oxygen remaining in the chamber during the Al film formation oxidizes Al and deteriorates the characteristics.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides an electronic device in which the contact resistance between a SiC semiconductor and an electrode is reduced, and a method for manufacturing the same. To aim.

[0007]

In order to solve the above-mentioned problems, the present invention provides a p-type or n-type SiC semiconductor portion, and a SiC semiconductor portion provided on the SiC semiconductor portion and extending from the surface of the SiC semiconductor portion. There is provided a carbon electrode containing the carbon nanotubes described above.

The present invention also provides p-type or n-type SiC.
The method includes the step of forming a carbon electrode containing carbon nanotubes extending from the surface of the SiC semiconductor part on the semiconductor part, and the step of forming the carbon electrode includes vacuum heating the SiC semiconductor part to form the SiC semiconductor part. A method for manufacturing an electronic device, comprising desorbing Si atoms contained in the surface region of C and bonding C atoms together to grow carbon nanotubes.

Furthermore, the present invention provides p-type or n-type Si.
A C semiconductor substrate, a cathode electrode provided on the SiC semiconductor substrate, and an anode electrode provided on the SiC semiconductor substrate, wherein at least one of the cathode electrode and the anode electrode is the SiC semiconductor substrate. There is provided a semiconductor device including a carbon electrode including a carbon nanotube provided on the SiC semiconductor portion and extending from a surface of the SiC semiconductor portion.

The present invention also provides p-type or n-type SiC.
A semiconductor substrate; a source electrode provided on the SiC semiconductor substrate; a drain electrode provided on the SiC semiconductor substrate; and a gate electrode provided on the SiC semiconductor substrate. At least one of the drain electrode and the gate electrode is the Si
There is provided a semiconductor device comprising a carbon electrode including a carbon nanotube provided on a C semiconductor substrate and extending from a surface of the SiC semiconductor portion.

The term "electronic device" as used herein means a device using electrical conduction such as a semiconductor device such as a high breakdown voltage semiconductor device, a light emitting diode, and an LSI.

In the present invention, a metal layer may be provided on the carbon electrode. In addition, in the present invention, the carbon electrode may further include graphite in addition to the carbon nanotube. In this case, the carbon electrode can have, for example, a laminated structure of a carbon nanotube layer containing carbon nanotubes and a graphite layer interposed between the carbon nanotube layer and the SiC semiconductor portion and containing graphite.

In the method of the present invention, for heating the SiC semiconductor portion in vacuum, for example, a laser, an electric furnace, or a combination thereof can be used. In the method of the present invention, the step of forming the carbon electrode may further include supplying carbon to the surface of the SiC semiconductor portion to form an initial carbon nucleus prior to vacuum heating of the SiC semiconductor portion. In this case, the growth of the carbon nanotubes can be generated from the initial carbon nuclei, and therefore, the carbon electrode can be formed on the Si surface of the SiC semiconductor portion. In addition, in order to form the carbon initial nucleus on the surface of the SiC semiconductor part,
For example, C ion implantation, CVD using a C-based gas, PVD, or the like can be used.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or similar components are designated by the same reference numerals, and duplicated description will be omitted.

(First Embodiment) In the first embodiment,
A method of forming carbon nanotubes on a SiC substrate and a method of applying the same to form a carbon electrode will be described.

1 (a) to 1 (e) are schematic views showing a method of forming a carbon electrode according to the first embodiment of the present invention. 1 (a), 1 (c) to 1 (e) are sectional views, and FIG. 1 (b) is a perspective view of FIG. 1 (c). Further, FIG. 1E illustrates a wider range than that of FIGS. 1A to 1D.

In the method according to the present embodiment, first, as shown in FIG.
As shown in (a), a SiC substrate 1 having a Si (silicon) surface on the front surface and a C (carbon) surface on the back surface is prepared. Next, the SiC substrate 1 is cleaned with RCA (H ₂
O ₂ + H ₂ SO ₄ cleaning, water cleaning, diluted HF cleaning, water cleaning, NH ₄ O
H + H ₂ O ₂ + H ₂ O cleaning, water cleaning, diluted HF cleaning, water cleaning, H
Cl + H ₂ O ₂ + H ₂ O washing, washing with water, and dilute HF washing in this order).

Then, as shown in FIG.
Initial carbon nuclei 2 are formed on the Si surface of the substrate 1. This initial carbon nucleus 2 can be formed by using, for example, the CVD apparatus shown in FIG.

FIG. 2 shows the method shown in FIGS. 1 (a) to 1 (e).
It is a figure which shows schematically an example of the CVD apparatus which can be used.
The CVD apparatus shown in FIG. 2 has a circular tube type CVD furnace 51.
There is. The CVD furnace 51 includes a mass flow controller 52.
Gas supply via a, 52b and valves 53a, 53b
Sources 54a and 54b are connected to each other, gas supply
Source 52a to propane (C₃H₈) Gas and gas source
From 52b, hydrogen (H ₂) CVD furnace with gas at desired flow rate
It can be supplied within 51. In the CVD furnace 51,
A rotary pump 55 is connected to the CVD furnace 51.
The internal gas pressure can be controlled.

In forming the initial carbon nuclei 2 by using this CVD apparatus, first, the SiC substrate 1 which has been subjected to the above-mentioned cleaning treatment is carried into the CVD furnace 51. Then, the pump 55
C to drive the inside of the CVD furnace 51 to a predetermined depressurized state, and
By supplying H ₂ gas and C ₃ H ₈ gas into the VD furnace 51 and thermally decomposing these gases, Si of the SiC substrate 1
A carbon cluster having a particle size of several Å to several tens of Å is formed on the surface as an initial carbon nucleus 2. Specifically, after the SiC substrate 1 is mounted on the mounting table of the CVD furnace 51 shown in FIG. 2, the atmosphere in the CVD furnace 51 is exhausted by the pump 55 (1.0 × 10 5
^-2 Pa or less) and replacement with H ₂ gas are repeated,
The inside of the CVD furnace 51 is heated while supplying H ₂ gas at a flow rate of 500 sccm. Circular tube temperature is 500 ℃ ~ 1100 ℃,
Preferably, when the temperature reaches 800 ° C to 1000 ° C, CV
By introducing C ₃ H ₈ gas into the D furnace 51 at a flow rate of 50 sccm and thermally decomposing them, carbon of several Å to several tens of Å is formed on the Si surface of the SiC substrate 1 as shown in FIG. 1B. Clusters 2 can be formed.

Although propane (C ₃ H ₈ ) was used as the carbon source here, other hydrocarbons such as ethylene and acetylene can also be used. Next, the SiC substrate 1 having the carbon clusters 2 formed on the Si surface is carried into an electric furnace equipped with an induction heating type carbon heater, for example. Then, the pressure inside the electric furnace was reduced to 1.0 × 10 ^-2 Pa or less,
The temperature is raised to 1200 to 1800 ° C.

When such a vacuum heat treatment is performed, first,
As shown in FIG. 1C, Si atoms are selectively desorbed from the surrounding portion of the carbon clusters 2 of the SiC substrate 1, and along with that, the C atoms having a bond due to the desorption of Si are recombined with each other. . As a result, as shown in FIG.
A large number of carbon nanotubes 3 extending from the Si surface of the C substrate 1 are formed. These carbon nanotubes 3
1 by continuing the above vacuum heat treatment.
As shown in (e), the surface region of the SiC substrate 1 is used as a raw material for further growth. As described above, the SiC substrate 1
A carbon electrode 5 containing the carbon nanotubes 3 extending from the surface of the carbon nanotube is obtained.

The fact that the carbon electrode 5 contains the carbon nanotube 3 can be easily confirmed by observing with a TEM. According to TEM observation, usually, in the carbon electrode 5 obtained by such a method, the carbon nanotubes 3 are oriented substantially perpendicular to the substrate surface, and there is almost no space between the adjacent carbon nanotubes 3. Are arranged so densely that there are no. The carbon nanotubes 3 obtained by such a method have a diameter of about 3 nm to 12 nm and a density of about 1 × 10 ^{11 to} 5 × 10 ¹³ pieces / cm ² .

In the method described above, the carbon clusters 2 are formed by using thermal CVD, but the carbon clusters 2 can be formed by using plasma CVD. For example, the SiC substrate 1 that has been subjected to RCA cleaning is subjected to plasma CV
He gas, H ₂ gas, CH ₄ gas, and CF ₄ gas are loaded into the D chamber and 50 sccm and 5 sc, respectively.
cm, 1 sccm, 30 sccm, the total temperature is 4.0 × 10 ⁴ Pa, the substrate temperature is 300 ° C.,
The carbon cluster 2 can be formed on the surface of the SiC substrate 1 by performing a deposition process for about 10 to 100 seconds with an input power of 100 W. Even when the carbon clusters 2 are formed by such a method, thermal CV
The same effect as when D is used can be obtained.

The carbon clusters 2 can also be formed by using sputtering. Similar results can be obtained by using sputtering. For example, RC
After the cleaned SiC substrate 1 was loaded into the sputtering chamber, the back pressure inside the chamber was 1.0 × 10 ⁻³ Pa.
Further, the inside of the chamber is set to an Ar atmosphere of 6.7 × 10 ⁻¹ Pa, a discharge is generated with an input power of 100 W, and plasma is made to collide with a carbon target, whereby carbon clusters are formed on the Si surface of the SiC substrate 1. 2 can be formed. Even when the carbon cluster 2 is formed by such a method, it is possible to obtain the same effect as in the case of using the thermal CVD.

Although carbon clusters are formed as the initial carbon nuclei 2 by the vapor deposition method as described above, the initial carbon nuclei 2 can also be formed by C ion implantation. This will be described with reference to FIG.

FIG. 3 is a cross-sectional view schematically showing a method of forming initial carbon nuclei using the ion implantation method. The initial carbon nucleus 2 is formed by C ion implantation, for example, by the following method. First, the RCA-cleaned SiC substrate 1 is carried into the ion implantation apparatus. Next, C is implanted into the Si surface of the SiC substrate 1 at an acceleration voltage of C ion implantation of 10 to 50 keV, more preferably about 30 keV, and a total dose amount of 1 × 10 ¹⁶ to 1 × 10 ¹⁷ cm ^−3. . afterwards,
The SiC substrate 1 is heat-treated at about 1200 to 1500 ° C. Thereby, as shown in FIG. 3, C injected into the surface region of SiC substrate 1 changes to carbon cluster 2. Even when the carbon cluster 2 is formed by such a method, it is possible to obtain the same effect as in the case of using the thermal CVD.

The formation of the carbon electrode 5 containing the carbon nanotubes 3 on the Si surface of the SiC substrate 1 has been described above, but the carbon nanotubes 3 are also formed on the C surface of the SiC substrate 1 by the same method as described above. The included carbon electrode 5 can be formed. In addition, S of the SiC substrate 1
Unlike the i-plane, since carbon is present on the C-plane of the SiC substrate 1, it is not necessary to form the initial carbon nuclei 2 when forming the carbon electrode 5 on the C-plane of the SiC substrate 1. That is,
For example, the SiC substrate 1 is placed under a pressure of 1.0 × 10 ^-2 Pa or less in an electric furnace equipped with an induction heating type carbon heater.
By heating to 200 to 1800 ° C., the carbon electrode 5 similar to the above can be formed on the C surface of the SiC substrate 1.

It has been conventionally known that carbon nanotubes can be formed on the C surface of a SiC substrate by vacuum heat treatment, but it cannot be formed on the Si surface. (M. Kusunokiet al. Appl.
Phys. Lett. , Vol. 77, No. 4,
531 (2000)). However, as described above, by forming the carbon initial nucleus 2, Si of the SiC substrate 1
It becomes possible to form the carbon nanotubes 3 on the surface as well. That is, the carbon nanotubes can be formed without being restricted by the surface, and thus the combination of the SiC substrate 1 and the carbon electrode 5 described above can be used in various electronic devices.

In the method described above, the carbon nanotubes 3 are formed by recombining C atoms existing in the SiC substrate 1. Therefore, the SiC substrate 1 and the carbon nanotubes 3 are atomically bound to each other. ing. Therefore, the contact resistance between the carbon electrode 5 and the SiC substrate 1 obtained by such a method is extremely low.

For example, when the carbon electrode 5 is formed on the Si surface of the SiC substrate 1 having the n-type impurity concentration of 1 × 10 ¹⁸ cm ⁻³ or more by the above method, the SiC substrate 1 and the carbon electrode 5 are formed.
The contact resistance ρc with is 1 × 10 ⁻⁶ Ωcm ² or less, and the p-type impurity concentration is 1 × 10 ¹⁸ cm 2 by the above method.
^-3 or more, when the carbon electrode 5 is formed on the Si surface of the SiC substrate 1, the contact resistance ρc between the SiC substrate 1 and the carbon electrode 5
Was 1 × 10 ⁻⁵ Ωcm ² or less. On the other hand, when the carbon electrode 5 is formed on the C surface of the SiC substrate 1 having the n-type impurity concentration of 1 × 10 ¹⁸ cm ⁻³ or more by the above method, Si
The contact resistance ρc between the C substrate 1 and the carbon electrode 5 is 1 × 10 ^-6 Ω
cm ² or less, and when the carbon electrode 5 is formed on the C surface of the SiC substrate 1 having the p-type impurity concentration of 1 × 10 ¹⁸ cm ⁻³ or more by the above method, the SiC substrate 1 and the carbon electrode 5 are Had a contact resistance ρc of 1 × 10 ⁻⁵ Ωcm ² or less.

On the other hand, Japanese Patent Laid-Open No. 2000-294119
The carbon nanotube film obtained by preliminarily forming carbon nanotubes by the method disclosed in Japanese Patent Laid-Open Publication No.
The contact resistance with the iC substrate was examined. As a result, their contact resistance ρc was a very large value of 1 × 10 ⁻¹ Ωcm ² or more.

From the above, it can be seen that when the SiC substrate and the carbon nanotubes are atomically bonded, a contact resistance much lower than that when the SiC substrate and the carbon nanotubes are simply contacted with each other can be realized. .

Further, the carbon electrode 5 obtained by the method according to the present embodiment has a structure in which a large number of carbon nanotubes 3 are juxtaposed on the SiC substrate 1, and therefore has a very large surface area. Therefore, the carbon electrode 5 has excellent heat dissipation. Further, as described above, in the structure obtained in the present embodiment, since the SiC substrate and the carbon nanotubes are atomically bonded to each other, compared to the structure obtained by adhering the carbon nanotubes to the SiC substrate, etc. The adhesion between the substrate and the carbon nanotube is much higher. Therefore, in the structure obtained in the present embodiment, peeling of the carbon electrode 5 from the SiC substrate is unlikely to occur. Thus, according to the present embodiment, it is possible to form a carbon electrode having a low contact resistance with the SiC substrate and excellent heat dissipation and mechanical strength.

In the method according to this embodiment, the length of the carbon nanotube 3 can be controlled according to the temperature and time of the vacuum heat treatment. That is, usually, the longer carbon nanotube 3 is obtained by performing the vacuum heat treatment at a higher temperature and / or for a longer time.
Can be formed. For example, when the above vacuum heat treatment is carried out at a temperature of 1200 ° C. for 0.5 hours under a pressure of 1.0 × 10 ⁻² Pa or less, carbon nanotubes 3 having a length of about 5 nm can be obtained. When the vacuum heat treatment is performed at a temperature of 1400 ° C. for 0.5 hours, carbon nanotubes 3 having a length of about 50 nm can be obtained, and the vacuum heat treatment is performed at a temperature of 1600 ° C. for 0.5 hours.
The carbon nanotubes 3 having a length of about 300 nm can be obtained when the process is performed for a long time.

However, when the thickness of the carbon electrode 5 (average length of the carbon nanotubes 3) exceeds 1 μm,
The difference in the coefficient of thermal expansion between the SiC substrate 1 and the carbon electrode 5 causes strain in the joint between them, resulting in S
A crack may occur in the carbon electrode 5 in the vicinity of the iC substrate 1 and a part thereof may be peeled off. If such peeling occurs,
The contact resistance increases to about 1.0 × 10 ^-2 Ωcm ^2, for example. Therefore, the thickness of the carbon electrode 5 (average length of the carbon nanotubes 3) is preferably 1 μm or less.

In the method according to this embodiment, graphite can be mixed in the carbon electrode 5. Normally,
As shown in (b), when the SiC substrate 1 having the carbon clusters 2 formed on the Si surface is heated to a temperature of 1800 to 2000 ° C. higher than the formation temperature of carbon nanotubes, the SiC
Rather than carbon nanotubes, randomly oriented graphite is formed on the substrate 1. On the other hand, unlike the case of the Si surface, graphite can be formed on the C surface of the SiC substrate 1 by the same heat treatment regardless of the presence or absence of the carbon cluster 2.

Therefore, for example, by setting the heating temperature at the time of the vacuum heat treatment as a temperature at which carbon nanotubes are mainly formed and then at a temperature at which graphite is mainly formed, for example, from the SiC substrate 1 side to the graphite layer. The carbon electrode 5 having a structure in which the carbon nanotube layers are sequentially stacked can be formed. Even when such a carbon electrode 5 is formed,
It was possible to obtain almost the same effect as when the carbon electrode 5 contained only the carbon nanotube 3.

(Second Embodiment) In the second embodiment,
The method of forming the carbon electrode described in the first embodiment is used for manufacturing the n-type Schottky diode.

FIGS. 4A to 4F are sectional views schematically showing a method for manufacturing an n-type Schottky diode according to the second embodiment of the present invention. In the present embodiment, FIG.
The n-type Schottky diode shown in (f) is manufactured by the method described below.

First, as shown in FIG. 4A, an n-type SiC substrate 12 having a Si surface on one surface is prepared. Here, the SiC substrate 12 has an n-type impurity concentration of 1 × 1.
An n-type high resistance layer having an impurity concentration of 5 × 10 ¹⁵ cm ⁻³ and a thickness of 10 μm is formed by an epitaxial method on a low resistance substrate 10 made of SiC having a thickness of 0 ¹⁹ cm ⁻³ and a thickness of 300 μm. What formed 11 is used. Instead of using N (nitrogen) as the n-type impurity, another n-type impurity such as P (phosphorus) may be used. Alternatively, both of them may be used.

Next, regarding the carbon electrode 5 in the first embodiment,
As shown in Fig. 4 (b), using the same method as described above.
Surface of the low resistance substrate 10 on which the n-type high resistance layer 11 is formed
The carbon electrode 13 is formed on the back surface (C surface) of the. This carbon electric
The electrode 13 is used as a cathode electrode. Then, n-type high resistance
A thin film made of an oxide film or metal is formed on the anti-layer 11.
Form turn 18. Furthermore, this thin film pattern 18
N-type high resistance by using ion implantation as a mask
A p-type impurity ion such as B (boron) is formed in the surface region of the layer 11.
Inject. After that, heat treatment at about 1600 ° C
Guard ring 14 is activated by activating the implanted ions.
Form. Here, B (boron) ions are added
Fast energy of 10 to 350 keV, total dose of 1.
6 x 10 ¹³cm^-2N-type high resistance layer
11 into the region from the surface to a depth of about 0.7 μm
It was As a result, the impurity concentration is 2 × 10.¹⁷cm^-3Guard
Ring 14 was obtained.

After removing the thin film pattern 18 from the n-type high resistance layer 11, as shown in FIG. 4 (c), the n-type high resistance layer 1 is formed.
Thin film pattern 1 made of oxide film or metal on 1
9 is formed. Next, using this thin film pattern 19 as a mask, n-type impurity ions such as P (phosphorus) are implanted into the surface region of the n-type high resistance layer 11 by an ion implantation method. Then, heat treatment is performed to activate the implanted ions, so that the depletion layer limiting region 15 is formed outside the guard ring 14. Here, P (phosphorus) ions have an acceleration energy of 10 to 200 keV and a total dose of 5 × 10 ¹⁵ cm ^-2.
Then, the multi-stage implantation was performed to the region from the surface of the n-type high resistance layer 11 to a depth of about 0.3 μm. As a result, a depletion layer confined region 15 having an impurity concentration of 1 × 10 ²⁰ cm ⁻³ was obtained.

In the above process, the activation process for forming the guard ring 14 and the activation process for forming the depletion layer limiting region 15 are separately performed.
You may go at the same time. Further, as p-type impurity ions, B
(Boron) ion is used, and P is used as an n-type impurity ion.
Although (phosphorus) is used, the present invention is not limited thereto, and Al (aluminum) or the like may be used as the p-type impurity ion and N (nitrogen) or the like as the n-type impurity ion.

After removing the thin film pattern 19 from the n-type high resistance layer 11, as shown in FIG. 4 (d), an insulating film 16 such as a silicon oxide film is formed by photolithography and RIE. The high-resistance layer 11 is formed so as to cover the exposed surface between the guard ring 14 and the depletion layer limiting region 15. The insulating film 16 may cover a part of the guard ring 14 or the depletion layer limiting region 15.

Next, as shown in FIG. 4E, a Ti film 20 used as an anode electrode is formed on the surface of the SiC substrate 12 on which the insulating film 16 is formed. For forming the Ti film 20, electron beam evaporation, CVD method, sputtering method, or the like can be used.

Further, as shown in FIG. 4F, the Ti film 20 is patterned by using the photolithography method and the RIE method to form the anode electrode 20. Specifically, first, a thin film pattern is formed on the Ti film 20 corresponding to the region where the anode electrode is to be formed. Then, the Ti film 20 is etched using this thin film pattern as an etching mask to form an anode electrode. Then, the thin film pattern is removed from the anode electrode 20 to obtain an n-type Schottky diode in which the anode electrode 20 and the n-type high resistance layer 11 are Schottky junctions.

In the Schottky diode obtained by the above-mentioned method, the cathode electrode 13 is formed by the same method as described for the carbon electrode 5 in the first embodiment. Therefore, in this diode, the contact resistance between the cathode electrode 13 and the low resistance substrate 10 is 1 × 10 ^−6.
It was an extremely low value of about Ωcm ⁻² . Moreover, when this diode was subjected to a high temperature operation test at 300 ° C., the contact resistance between the cathode electrode 13 and the low resistance substrate 10 was 1 or less.
It did not change for more than 000 hours. in this way,
According to this embodiment, a Schottky diode having excellent long-term stability under high temperature conditions can be realized.

In the second embodiment, a carbon electrode containing only carbon nanotubes was formed as the cathode electrode 13, but a carbon electrode further containing a randomly oriented graphite layer between the substrate 12 and the carbon nanotube layer. Even in the case of forming, it is possible to obtain substantially the same effect. Further, a metal film may be formed on the surface of the carbon electrode, and a combination of the carbon electrode and the metal film may be used as the cathode electrode. In this case, the electrical characteristics and heat dissipation of the cathode electrode are made uniform over the entire electrode, which is advantageous from the viewpoint of high-temperature operation of the device. Further, in the above-described embodiment, the case where the n-type SiC semiconductor substrate is used as the SiC substrate 12 has been described, but the same effect can be obtained even when the p-type SiC semiconductor substrate is used.

A pn diode can be manufactured by slightly modifying a part of the process described with reference to FIGS. 4 (a) to 4 (f). This will be described with reference to FIG.

FIG. 5 shows p according to the second embodiment of the present invention.
It is sectional drawing which shows an n-diode schematically. The pn diode shown in FIG. 5 has, for example, the p-type region 21 and the p ⁺ -type low region shown in FIG. 5 instead of the p-type guard ring region 14 in the step of forming the guard ring 14 shown in FIG. It can be obtained by forming the resistance region 17.

(Third Embodiment) In the third embodiment,
The method of forming the carbon electrode described in the first embodiment is used for manufacturing the n-type Schottky diode. Unlike the second embodiment, the third embodiment applies the technique described in the first embodiment to not only the cathode electrode but also the anode electrode.

6A to 6C are sectional views schematically showing a method of manufacturing an n-type Schottky diode according to the third embodiment of the present invention. The method according to this embodiment is the same as the method for manufacturing the n-type Schottky diode according to the second embodiment up to the step shown in FIG. 4D. Therefore, here, only differences from the manufacturing method according to the second embodiment will be described.

In manufacturing the n-type Schottky diode shown in FIG. 6C, first, the structure shown in FIG. 4D is obtained. Next, as shown in FIG. 6A, the surface (Si surface) of the n-type high resistance layer 11 is formed by the same method as described in the first embodiment using the CVD apparatus shown in FIG. The carbon clusters 2 are formed on.

Next, the laser beam is irradiated to the n-type high resistance layer 11 having the carbon clusters 2 formed on the surface thereof. Here, for example, a YAG laser is used and its output is 0.5 to 2.5 Jcm ^-2 , preferably 1.0 to
It will be 2.0 Jcm ^-2 . As a result, as shown in FIG. 6B, the carbon nanotubes 3 are formed on the n-type high resistance layer 11.
Carbon electrode containing carbon nanotubes that grows carbon
3 is formed. In this embodiment, this carbon electrode 23 is used as an anode electrode.

Further, as shown in FIG. 6C, the carbon clusters 2 remaining on the insulating film 16 are removed by photolithography and RIE. As described above, a Schottky diode in which the anode electrode 23 and the n-type high resistance layer 11 have a Schottky junction is obtained.

In the Schottky diode obtained by the above-mentioned method, both the cathode electrode 13 and the anode electrode 23 are formed by the same method as described for the carbon electrode 5 in the first embodiment. Therefore, in this diode, the contact resistance between the cathode electrode 13 and the low resistance substrate 10 was a sufficiently low value of about 1 × 10 ⁻⁶ Ωcm ⁻² . Further, when this diode was subjected to a high temperature operation test at 300 ° C., the contact resistance between the cathode electrode 13 and the low resistance substrate 10 and the contact resistance between the anode electrode 23 and the n-type high resistance layer 11 were both determined. Also did not change for more than 1000 hours. As described above, according to the present embodiment, it is possible to realize a Schottky diode having excellent long-term stability under high temperature conditions.

In the third embodiment, carbon electrodes containing only carbon nanotubes are formed as the cathode electrode 13 and the anode electrode 23, but a graphite layer randomly oriented is further provided between the substrate 12 and the carbon nanotube layer. Even when a carbon electrode containing carbon is formed, substantially the same effect can be obtained. Further, a metal film may be formed on the surface of the carbon electrode, and a combination of the carbon electrode and the metal film may be used as the cathode electrode or the anode electrode. In this case, the electrical characteristics and heat dissipation of the cathode electrode or the anode electrode are made uniform over the entire electrode, which is advantageous from the viewpoint of high-temperature operation of the device. further,
In the above embodiment, n-type SiC is used as the SiC substrate 12.
The case where a semiconductor substrate is used has been described, but p-type Si is used.
Similar effects can be obtained when a C semiconductor substrate is used.

Similar to the second embodiment, a pn diode can be manufactured by slightly changing a part of the above-mentioned process. This will be described with reference to FIG.

FIG. 7 shows p according to the third embodiment of the present invention.
It is sectional drawing which shows an n-diode schematically. In the pn diode shown in FIG. 7, for example, in the process of forming the guard ring 14 shown in FIG. 4B, instead of the p-type guard ring region 14, the p-type region 21 and the p ⁺ -type low region shown in FIG. It can be obtained by forming the resistance region 17 and carrying out otherwise the same process as described above.

(Fourth Embodiment) In the fourth embodiment,
The method of forming the carbon electrode described in the first embodiment is used for manufacturing the n-type Schottky diode. In the fourth embodiment, the technique described in the first embodiment is applied to both the cathode electrode and the anode electrode similarly to the third embodiment, but unlike the third embodiment, those electrodes are simultaneously applied. Form.

8A to 8D are sectional views schematically showing a method of manufacturing an n-type Schottky diode according to the fourth embodiment of the present invention. In manufacturing the n-type Schottky diode shown in FIG. 8D, first, as shown in FIG.
The structure shown in (a) is obtained. 8A except that the cathode electrode 13 is not provided.
It is similar to the structure shown in (d). Here, a silicon nitride film is used as the insulating film 16.

Next, by using the CVD apparatus shown in FIG. 2 and by the same method as described in the first embodiment, as shown in FIG.
As shown in (b), the surface of the n-type high resistance layer 11 (Si
A carbon cluster 2 is formed on the surface.

Next, the substrate 12 having the carbon clusters 2 formed on its surface is subjected to vacuum heat treatment in an electric furnace equipped with an induction heating type carbon heater. As a result, FIG.
As shown in (c), carbon nanotubes 3 are grown on the surfaces of the low resistance substrate 10 and the n-type high resistance layer 11, respectively, to form carbon electrodes 13 and 23 containing carbon nanotubes, respectively. In this embodiment, these carbon electrodes 13 and 23 are used as a cathode electrode and an anode electrode, respectively.

Further, as shown in FIG. 8D, the carbon clusters 2 remaining on the insulating film 16 are removed by photolithography and RIE. As described above, a Schottky diode in which the anode electrode 23 and the n-type high resistance layer 11 have a Schottky junction is obtained.

In the Schottky diode obtained by the above-mentioned method, both the cathode electrode 13 and the anode electrode 23 are formed by the same method as described for the carbon electrode 5 in the first embodiment. Therefore, in this diode, the contact resistance between the cathode electrode 13 and the low resistance substrate 10 was a sufficiently low value of about 1 × 10 ⁻⁶ Ωcm ⁻² . Further, when this diode was subjected to a high temperature operation test at 300 ° C., the contact resistance between the cathode electrode 13 and the low resistance substrate 10 and the contact resistance between the anode electrode 23 and the n-type high resistance layer 11 were both determined. Also did not change for more than 1000 hours. As described above, according to the present embodiment, it is possible to realize a Schottky diode having excellent long-term stability under high temperature conditions.

In the fourth embodiment, a metal film may be formed on the surface of the carbon electrode, and the combination of the carbon electrode and the metal film may be used as the cathode electrode or the anode electrode. In this case, the electrical characteristics and heat dissipation of the cathode electrode or the anode electrode are made uniform over the entire electrode, which is advantageous from the viewpoint of high-temperature operation of the device. Further, in the above-described embodiment, the case where the n-type SiC semiconductor substrate is used as the SiC substrate 12 has been described, but the same effect can be obtained even when the p-type SiC semiconductor substrate is used.

Further, similar to the third embodiment, p shown in FIG. 7 is obtained by slightly changing a part of the above-mentioned process.
n-diodes can be manufactured. That is, FIG.
In the pn diode shown in FIG. 4A, for example, in the step of forming the guard ring 14 shown in FIG. The region 17 is formed, and otherwise, it can be formed by performing the same process as described above.

As described above, in this embodiment, the vacuum heat treatment for forming the cathode electrode 13 and the vacuum heat treatment for forming the anode electrode 23 are simultaneously performed. That is, according to the present embodiment, the Schottky diode can be manufactured by a more simplified process.

(Fifth Embodiment) In the fifth embodiment,
The method of forming the carbon electrode described in the first embodiment is used for manufacturing the n-type static induction transistor.

9A to 9G are sectional views schematically showing a method of manufacturing an n-type static induction transistor according to the fifth embodiment of the present invention. In the present embodiment, FIG.
The n-type static induction transistor shown in is manufactured by the method described below.

First, as shown in FIG. 9A, S is formed on one surface.
An n-type SiC substrate 12 having an i-plane is prepared. Here, as the SiC substrate 12, the n-type impurity concentration is 1 × 10.
^{On the} low resistance substrate 10 made of SiC having a thickness of ¹⁹ cm ⁻³ and a thickness of 300 μm, an n-type impurity concentration of 5 × 10 ¹⁵ cm ⁻³ and a thickness of 10 μm was obtained by an epitaxial method.
It is assumed that the mold high resistance layer 11 is used.
Instead of using N (nitrogen) as the n-type impurity,
Other n-type impurities such as P (phosphorus) may be used. Also, both of them may be used. Next, this SiC substrate 1
By subjecting 2 to a vacuum heating treatment in an electric furnace equipped with an induction heating type carbon heater, a carbon electrode 31 containing carbon nanotubes is formed as a drain electrode on the back surface (C surface) of the SiC substrate 12.

Next, the surface of the SiC substrate 12 (Si surface)
By sequentially performing ion implantation into the substrate and activation heat treatment, n ⁺ becomes a source region in the surface region of the SiC substrate 12.
Form an area. Specifically, first, as shown in FIG. 9B, a thin film pattern 33 made of metal or oxide is formed on the surface of the substrate 12. Then, using the thin film pattern 33 as a mask, P is formed by an ion implantation method.
An n-type impurity such as (phosphorus) is injected into the surface region of the n-type high resistance layer 11. Further, the substrate 12 is subjected to heat treatment at about 1600 ° C. to activate the implanted ions and form the source region 32. Here, P (phosphorus) ions have an acceleration energy of 10 to 200 keV and a total dose of 5 ×.
The n-type high resistance layer 11 is formed by multi-step implantation at 10 ¹⁵ cm ^-2.
Was injected into the region from the surface of the to a depth of about 0.3 μm.
As a result, the source region 32 having an impurity concentration of 1 × 10 ²⁰ cm ⁻³ was obtained.

After removing the thin film pattern 33 from the n-type high resistance layer 11, as shown in FIG. 9C, the n-type high resistance layer 1 is formed.
A p-type impurity is diffused at a high concentration in the surface region 1 to form a gate region 34 outside the n-type source region 32. Specifically, first, an insulating film 35 such as a patterned oxide film or nitride film is formed on the upper surface of the n-type high resistance SiC substrate. Then, using the patterned insulating film 35 as a mask, p-type impurities such as B (boron) are implanted into the surface region of the n-type high resistance layer 11 by an ion implantation method.
Further, the substrate 12 is heat-treated at about 1600 ° C. to activate the implanted ions and form the gate region 34.

Here, B (boron) ions have an acceleration energy of 10 to 350 keV and a total dose of 8 × 10.
^It was implanted at a depth of about 0.7 μm from the surface of the n-type high resistance layer 11 by multi-stage implantation at ¹⁴ cm ⁻² . As a result, the gate region 34 having an impurity concentration of 1 × 10 ¹⁹ cm ⁻³
was gotten.

Next, as shown in FIG. 9D, the insulating film 35 is formed by photolithography and RIE.
Of the n-type source region 32 is selectively removed. The insulating film 35 patterned in this way
Is at least the n-type source region 32 of the n-type high resistance layer 11.
And the p-type gate region 34, the n-type source region 32 or the p-type gate region 34 may be formed.
May be partially covered.

Next, in the first embodiment, as shown in FIG.
By the same method as described with reference to FIG.
As shown in (e), the surface of the n-type high resistance layer 11 (Si
A carbon cluster 2 having a particle size of several Å to several tens of Å is formed on the surface. Further, as shown in FIG. 9F, the n-type high resistance layer 11 having the carbon clusters 2 formed on the surface is irradiated with a laser beam. Here, for example, using the YAG laser, the output 0.5～2.5Jcm ^-2, preferably a 1.0~2.0Jcm ^-2. As a result, the carbon nanotubes 3 are grown on the n-type high resistance layer 11, and the carbon electrodes 39 containing the carbon nanotubes 3,
Get 40. In this embodiment, the carbon electrode 39 is used as a source electrode and the carbon electrode 40 is used as a gate electrode.

Further, as shown in FIG. 9G, the carbon clusters 2 remaining on the insulating film 35 are removed by the photolithography method and the RIE method. As described above, the static induction transistor shown in FIG. 9G is obtained.

In the electrostatic induction transistor obtained by the method described above, the drain electrode 31, the source electrode 39, and the gate electrode 40 are all formed by the same method as described for the carbon electrode 5 in the first embodiment. is doing. Therefore, in this transistor, the contact resistance between the source electrode 39 and the n-type source region 32 is 1 × 10 ⁻⁶ Ωc.
The contact resistance between the gate electrode 40 and the p-type gate region 34 is 1 × 10 ⁻⁵ Ωcm ⁻² , which is a sufficiently low value of m ⁻² or less.
The contact resistance between the low resistance substrate 10 and the drain electrode 31 was 1 × 10 ⁻⁶ Ωcm ⁻² or less, which was a sufficiently low value.

In the fifth embodiment, the drain electrode 31,
In the case where a carbon electrode containing only carbon nanotubes was formed as the source electrode 39 and the gate electrode 40, but a carbon electrode further containing a randomly oriented graphite layer was formed between the substrate 12 and the carbon nanotube layer. Can obtain almost the same effect. Alternatively, a metal film may be formed on the surface of the carbon electrode, and a combination of the carbon electrode and the metal film may be used as the drain electrode, the source electrode, or the gate electrode. In this case, the electrical characteristics and heat dissipation of these electrodes are made uniform over the entire electrodes, which is advantageous from the viewpoint of high-temperature operation of the device.
Furthermore, in the above embodiment, the case where an n-type SiC semiconductor substrate is used as the SiC substrate 12 has been described.
Similar effects can be obtained even when a type SiC semiconductor substrate is used.

(Sixth Embodiment) In the sixth embodiment,
The method of forming the carbon electrode described in the first embodiment is used for manufacturing the n-type static induction transistor. In the sixth embodiment, similar to the fifth embodiment, the technique described in the first embodiment is applied to the drain electrode, the source electrode, and the gate electrode, but unlike the fifth embodiment, those electrodes are used. Are formed at the same time.

10A to 10C are sectional views schematically showing a method for manufacturing an n-type static induction transistor according to the sixth embodiment of the present invention. In the present embodiment, FIG.
The n-type static induction transistor shown in (c) is manufactured by the method described below.

First, the structure shown in FIG. 10A is formed by the same method as described with reference to FIGS. 9A to 9E in the fifth embodiment except that the carbon electrode 31 is not formed. obtain. Note that here, a silicon nitride film is used as the insulating film 35.

Then, the substrate 12 having the carbon clusters 2 formed on its surface is subjected to a vacuum heating treatment in an electric furnace equipped with an induction heating type carbon heater. Thereby, the carbon nanotubes 3 are grown on the surfaces of the low resistance substrate 10 and the n-type high resistance layer 11, respectively, and the carbon electrodes 31, 39, 40 containing the carbon nanotubes are formed. In the present embodiment, these carbon electrodes 31, 39, 40
Are used as a drain electrode, a source electrode, and a gate electrode, respectively.

Further, as shown in FIG. 10C, the carbon cluster 2 remaining on the insulating film 35 is removed by the photolithography method and the RIE method. As described above, the static induction transistor shown in FIG. 10C is obtained.

In the electrostatic induction transistor obtained by the above-mentioned method, the drain electrode 31, the source electrode 39, and the gate electrode 40 are all formed by the same method as described for the carbon electrode 5 in the first embodiment. is doing. Therefore, in this transistor, the contact resistance between the source electrode 39 and the n-type source region 32 is 1 × 10 ⁻⁶ Ωc.
The contact resistance between the gate electrode 40 and the p-type gate region 34 is 1 × 10 ⁻⁵ Ωcm ⁻² , which is a sufficiently low value of m ⁻² or less.
The contact resistance between the low resistance substrate 10 and the drain electrode 31 was 1 × 10 ⁻⁶ Ωcm ⁻² or less, which was a sufficiently low value.

In the sixth embodiment, a metal film may be formed on the surface of the carbon electrode, and the combination of the carbon electrode and the metal film may be used as the drain electrode, the source electrode or the gate electrode. In this case, the electrical characteristics and heat dissipation of these electrodes are made uniform over the entire electrodes, which is advantageous from the viewpoint of high-temperature operation of the device. Further, in the above-described embodiment, the case where the n-type SiC semiconductor substrate is used as the SiC substrate 12 has been described, but the same effect can be obtained even when the p-type SiC semiconductor substrate is used.

Further, in the sixth embodiment, as described above, the vacuum heat treatment for forming the drain electrode 31 and the vacuum heat treatment for forming the source electrode 39,
The vacuum heat treatment for forming the gate electrode 40 is performed at the same time. That is, according to this embodiment, a more simplified electrostatic induction transistor can be manufactured.

[0089]

As described above, according to the present invention, Si
By desorbing Si atoms contained in the surface region of the C semiconductor portion and bonding the C atoms to each other, a carbon electrode containing carbon nanotubes extending from the surface is formed on the SiC semiconductor portion. Such carbon electrode and SiC
The contact resistance with the semiconductor part is extremely low. That is, according to the present invention, an electronic device in which the contact resistance between the SiC semiconductor and the electrode is reduced and a method for manufacturing the same are provided.

[Brief description of drawings]

1A to 1E are diagrams schematically showing a carbon electrode forming method according to a first embodiment of the present invention.

FIG. 2 is a C usable in the method shown in FIGS.
The figure which shows an example of a VD apparatus roughly.

FIG. 3 is a cross-sectional view schematically showing a method for forming initial carbon nuclei using an ion implantation method.

4A to 4F are cross-sectional views schematically showing a method for manufacturing an n-type Schottky diode according to the second embodiment of the present invention.

FIG. 5 is a sectional view schematically showing a pn diode according to a second embodiment of the present invention.

6A to 6C are sectional views schematically showing a method for manufacturing an n-type Schottky diode according to the third embodiment of the present invention.

FIG. 7 is a sectional view schematically showing a pn diode according to a third embodiment of the present invention.

8A to 8D are sectional views schematically showing a method for manufacturing an n-type Schottky diode according to the fourth embodiment of the present invention.

9A to 9G are sectional views schematically showing a method for manufacturing an n-type static induction transistor according to the fifth embodiment of the present invention.

10A to 10C are cross-sectional views schematically showing a method for manufacturing an n-type static induction transistor according to the sixth embodiment of the present invention.

[Explanation of symbols]

1 ... SiC substrate 2 ... Carbon initial nucleus 3 ... Carbon nanotube 5 ... Carbon electrode 12 ... SiC substrate 10 ... Low resistance substrate 11 ... n-type high resistance layer 13 ... Cathode electrode 14 ... Guard ring 15 ... Depletion layer restricted region 16 ... Insulating film 17 ... p-type low resistance region 18 ... Thin film pattern 19 ... Thin film pattern 20 ... Anode electrode 21 ... p-type region 23 ... Anode electrode 31 ... Drain electrode 32 ... Source area 33 ... Thin film pattern 34 ... Gate area 35 ... Insulating film 39 ... Source electrode 40 ... Gate electrode 51 ... Cylindrical CVD furnace 52a, 52b ... Mass flow controller 53a, 53b ... Valve 54a, 54b ... Gas supply source 55 ... Rotary pump

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 29/861 H01L 29/91 F 29/872 29/80 V 29/48 M D (72) Inventor Takashi Shinohe Kanagawa Komukai-shi, Kawasaki City Komukai-shi, 1st F-term in the R & D Center of Toshiba Corporation (Reference) 4M104 AA03 BB04 BB14 BB36 CC01 CC03 DD26 DD34 DD37 DD43 DD65 DD71 DD78 DD81 DD83 FF13 FF22 GG02 GG03 GG11 GG12 HH08 HH15 AH20 5F0 AB07 AD12 AD13 AD14 AE17 AF02 BB16 5F102 FB01 GB04 GC07 GD04 GJ02 GV00 HC00 HC07 HC21

Claims (5)

[Claims] 1. A p-type or n-type SiC semiconductor part, and a carbon electrode provided on the SiC semiconductor part and including carbon nanotubes extending from the surface of the SiC semiconductor part. Electronic device. 2. The electronic device according to claim 1, further comprising a metal layer on the carbon electrode. 3. A step of forming a carbon electrode containing carbon nanotubes extending from the surface of the SiC semiconductor portion on a p-type or n-type SiC semiconductor portion, the step of forming the carbon electrode comprising: Manufacture of an electronic device, comprising desorbing Si atoms contained in a surface region of the SiC semiconductor part and bonding C atoms to each other to grow carbon nanotubes by heating the semiconductor part in vacuum. Method. 4. The step of forming the carbon electrode comprises the step of
The method further comprises supplying carbon to the surface of the SiC semiconductor part to form carbon initial nuclei prior to vacuum heating of the iC semiconductor part, and causing growth of the carbon nanotubes from the carbon initial nuclei. The method of manufacturing an electronic device according to claim 3. 5. The method of manufacturing an electronic device according to claim 3, further comprising the step of forming a metal layer on the carbon electrode.