JP3651666B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly, to a Schottky device made of cubic 3C SiC and a manufacturing method thereof.
[0002]
[Prior art]
SiC crystal has about 10 times the breakdown electric field of Si and GaAs, about 2 times the saturation drift velocity of electrons, about 3 times the thermal conductivity of Si, and can control p and n conductivity, stable thermal oxide film It has an excellent feature that it can be formed, and is expected as a future power element material to replace Si.
[0003]
However, in order to produce hexagonal substrate crystals such as 4H and 6H, it is necessary to use an improved Rayleigh method of the high-temperature growth method, and at the present time, substrates having a maximum diameter of 2 inches are only commercially available. In addition, there are many large structural defects called micropipes in the substrate, which limits the portion that can be used in the wafer. For this reason, it has been difficult to mass-produce power elements using 4H, 6H-SiC crystals and to supply them stably.
[0004]
On the other hand, cubic 3C-SiC can be epitaxially grown on Si, so that the substrate can be enlarged and is suitable for mass production. However, 3C-SiC has the following problems.
[0005]
In order to produce a vertical SiC power element, it is necessary to form a cathode and an anode electrode on each surface of SiC. Therefore, it is necessary to remove the Si substrate, and a thick SiC epitaxial layer must be grown to increase the mechanical strength of the device. It is necessary to increase the growth rate so as not to increase the growth time even if the growth layer is thickened. Increasing the growth rate means that the SiC crystal is grown in a state far from the equilibrium state.
[0006]
As a result, a large number of anti-phase boundaries (APB) or twins observed when a compound semiconductor is epitaxially grown on a semiconductor are formed, and the Schottky characteristics that should be originally obtained cannot be obtained, resulting in ohmic characteristics. Found by the inventors. Furthermore, even if it is a 3C-SiC crystal that does not contain APB and twins, even if a Schottky metal is formed on it after normal pretreatment, good Schottky characteristics cannot be obtained, resulting in ohmic characteristics. Was also found by the inventors.
[0007]
[Problems to be solved by the invention]
As described above, the 4H and 6H-SiC crystals have a problem that a large-diameter and high-quality substrate cannot be produced, and the 3C-SiC crystals have a problem that a good Schottky element cannot be obtained. .
[0008]
This invention is made | formed in view of this situation, and it aims at providing the semiconductor element provided with the 3C-SiC crystal | crystallization which has a favorable Schottky characteristic, and its manufacturing method.
[0009]
[Means for Solving the Problems]
(Constitution)
In order to solve the above problems, a first aspect of the present invention includes a substrate on which a SiC region having a 3C-type crystal structure is formed on a surface, a metal layer that forms a Schottky junction with the SiC region, the SiC region, Provided is a semiconductor device comprising an insulating thin film having Si as a constituent element, which is interposed between a metal layer and allows current injection from the metal layer.
[0010]
In the first aspect of the present invention, the thin film is preferably made of SiO ₂ . Moreover, it is preferable that the thickness of this thin film is 1 nm or more and 5 nm or less. This is because if it is less than 1 nm, it is difficult to achieve the effect of the present invention, and if it exceeds 5 nm, it becomes difficult for current to flow.
[0011]
According to a second aspect of the present invention, there is provided a substrate having a 3C-type crystal structure SiC region formed on the surface, a metal layer forming a Schottky junction with the SiC region, and the SiC region and the metal layer. A method of manufacturing a semiconductor device having an insulating thin film containing Si as an interposing element and allowing current injection from the metal layer, wherein impurities are ion-implanted into a SiC region having a 3C crystal structure Thus, a method of manufacturing a semiconductor device is provided, wherein the insulating thin film is formed on the region.
[0012]
According to a third aspect of the present invention, there is provided a substrate having a 3C-type crystal structure SiC region formed on a surface, a metal layer forming a Schottky junction with the SiC region, and the SiC region and the metal layer. A method of manufacturing a semiconductor device having an insulating thin film containing Si as a constituent element, which intervenes and allows current injection from the metal layer, and etches a SiC region having a 3C-type crystal structure with a solution Thus, a method of manufacturing a semiconductor device is provided, wherein the insulating thin film is formed on the region.
[0013]
According to a fourth aspect of the present invention, there is provided a substrate having a 3C type crystal structure SiC region formed on a surface thereof, a metal layer forming a Schottky junction with the SiC region, and the SiC region and the metal layer. A method of manufacturing a semiconductor device including an insulating thin film containing Si as a constituent element, which allows current injection from the metal layer, and is a vapor phase growth method on a SiC region having a 3C crystal structure A method of manufacturing a semiconductor device is provided, wherein the insulating thin film is formed by the method described above.
[0014]
A fifth aspect of the present invention is a substrate having a 3C-type crystal structure SiC region formed on the surface, a metal layer forming a Schottky junction with the SiC region, and the SiC region and the metal layer. A method of manufacturing a semiconductor device including an insulating thin film having Si as a constituent element, which allows current injection from the metal layer, and includes a SiC region having a 3C-type crystal structure in the atmosphere for 5 days. There is provided a method for manufacturing a semiconductor device, characterized in that the insulating thin film is formed on the region by leaving it as described above.
[0015]
In the second to fifth aspects of the present invention, it is preferable to form a thin film made of SiO ₂ as the thin film.
[0016]
(Function)
The present invention proposes a good Schottky element structure using 3C-SiC crystals suitable for mass production. When APB and twins exist, the reason why the Schottky characteristic that should be originally obtained cannot be obtained and the ohmic characteristic is obtained is that a metallic level peculiar to 3C-SiC crystal exists. I found it. Even if they do not exist, when a Schottky element is manufactured by performing a normal pretreatment, the reason why the Schottky characteristic that should be originally obtained cannot be obtained and the ohmic characteristic is obtained is also a metal quasi characteristic peculiar to 3C-SiC crystals. This is because the position exists as a surface level.
[0017]
Therefore, when an insulating thin film containing Si as a constituent element that enables current injection from the metal layer is interposed between the 3C-SiC region and the metal layer forming the Schottky junction, a good Schottky is obtained. An element with characteristics could be fabricated.
[0018]
In such an insulating thin film, a material having insulating properties is usually used as a constituent material of the film. However, since the thickness of the film itself is very thin, current can be injected from the metal layer. When various materials were tested as the insulating thin film, the following were found to be appropriate. SiO ₂ film produced by various methods, 3C-SiC layer formed by ion implantation of impurities such as Ar, etc. 3C-SiC is produced by etching with a solution such as potassium carbonate solution A layer formed by vapor deposition on 3C-SiC, such as SiN. When producing | generating by vapor phase growth, it is possible to use monosilane, ammonia, etc. as source gas, for example. In addition, the present inventors have confirmed that a layer formed on the 3C-SiC surface by leaving the 3C-SiC surface in the atmosphere for 5 days or more is also effective.
[0019]
As described above, an insulating thin film containing Si as a constituent element that enables current injection from the metal layer is interposed between the 3C-SiC region and the metal layer that forms the Schottky junction. A device with excellent Schottky characteristics could be fabricated.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0021]
(First embodiment)
First, on a (100) surface of a 6-inch diameter Si substrate (1), an SiC layer (2) with an electron concentration of 3 × 10 ¹⁹ cm ⁻³ using silane (SiH ₄ ) and propane (C ₃ H ₈ ) as a source gas is 300 μm. Epitaxially grown. The growth rate was 50 μm / h. At that time, the conditions were adjusted so that the crystal did not grow in an island shape but grew in a step flow. Specifically, the temperature was raised to 1050 ° C. so as to increase lateral diffusion on the substrate, and low-pressure epitaxial growth was used to suppress the gas reaction in the gas phase. As a result, APB and twins were not present in the high electron concentration SiC layer (2). The wafer was taken out once, and the surface of the high electron concentration SiC layer (2) was polished to give a mirror surface.
[0022]
Thereafter, a SiC layer (3) having an electron concentration of 1 × 10 ¹⁵ cm ⁻³ was epitaxially grown by 15 μm. The growth rate at that time was 2 μm / h. At this time, the conditions were adjusted so that the crystal did not grow in an island shape but grew in a step flow. In this case as well, the growth conditions of the high electron concentration SiC layer (2) are almost the same, but the gas supply amount is 1/3. As a result, APB and twins were not present in the low electron concentration SiC layer (3). The situation so far is shown in FIG.
[0023]
Then, after removing the Si substrate (1), the wafer was dry oxidized at 1050 ° C. for 6 minutes to form a 3 nm silicon oxide film (3a). The dry oxidation atmosphere is 100% oxygen. Only the oxide film on the high electron concentration layer (SiC layer (2)) side is removed, and the Schottky electrode (4) is formed on the low electron concentration layer (SiC layer (3)) via the oxide film (3a). An ohmic electrode (5) was formed on the high electron concentration layer (2) to produce a Schottky element (FIG. 2). Good Schottky characteristics with a reverse breakdown voltage of 850 V were obtained. An IV characteristic is shown in FIG.
[0024]
(Comparative example)
The same process as in the first embodiment was performed until the Si substrate was removed. The situation so far is shown in FIG. (101) is a Si substrate, (102) is a high electron concentration SiC layer, and (103) is a low electron concentration SiC layer. Thereafter, after performing a normal pretreatment process, a Schottky electrode (104) was formed on the low electron concentration layer (103), and an ohmic electrode (105) was formed on the high electron concentration layer (102), thereby producing a Schottky element. (FIG. 4). The device characteristics were measured and found to be ohmic characteristics rather than Schottky characteristics. FIG. 5b (broken line) shows the IV characteristic.
[0025]
(Second Embodiment)
The same process as in the first embodiment was performed until the Si substrate was removed. Thereafter, Al was implanted into the low electron concentration layer at an acceleration voltage of 10 keV and a dose amount of 5 × 10 ¹² cm ⁻² , and the ultrathin surface layer was used as an insulating layer (corresponding to 3a with reference to FIG. 2). The composition of this insulating layer was amorphous SiC containing a large amount of Al, and the film thickness was 3 nm. A Schottky electrode (4) was formed thereon, and an ohmic electrode (5) was formed on the high electron concentration layer (2) to produce a Schottky element. Good Schottky characteristics with a reverse breakdown voltage of 800V were obtained. An IV characteristic is shown in FIG.
[0026]
(Third embodiment)
The same process as in the first embodiment was performed until the Si substrate was removed. Thereafter, a low electron concentration 3C-SiC (corresponding to 3 when FIG. 2 is used) was etched with a solution having a stable surface, for example, a potassium carbonate solution. An insulating layer was formed on the surface of the low electron concentration layer (3) as an ultrathin surface layer (corresponding to 3a with the aid of FIG. 2). The composition of this insulating layer was SiO ₂ and the film thickness was 1 nm. Further, a Schottky electrode (4) was formed on the low electron concentration layer (3), and an ohmic electrode (5) was formed on the high electron concentration layer (2) to produce a Schottky element. Good Schottky characteristics with a reverse breakdown voltage of 820 V were obtained. An IV characteristic is shown in FIG.
[0027]
(Fourth embodiment)
The same process as in the first embodiment was performed until the Si substrate was removed. Thereafter, a thin insulating layer (corresponding to 3a with the aid of FIG. 2) was formed on the surface of the low electron concentration layer (corresponding to 3 with the aid of FIG. 2) by vapor phase growth. Monosilane and ammonia were used as source gases, and the film forming conditions were reduced. The composition of this insulating layer was SiN, and the film thickness was 2 nm. Further, a Schottky electrode (4) was formed on the low electron concentration layer (3), and an ohmic electrode (5) was formed on the high electron concentration layer (2) to produce a Schottky element. Good Schottky characteristics with a reverse breakdown voltage of 860V were obtained. An IV characteristic is shown in FIG.
[0028]
(Fifth embodiment)
The same process as in the first embodiment was performed until the Si substrate was removed. Thereafter, the sample was left in the atmosphere for 10 days to form a thin insulating layer (corresponding to 3a with the aid of FIG. 2) on the surface of the low electron concentration layer (corresponding to 3 with the aid of FIG. 2). The composition of this insulating layer was SiO ₂ containing N, and the film thickness was 1 nm. Here, the atmosphere of air was humidity 50%. Further, a Schottky electrode (4) was formed on the low electron concentration layer (3), and an ohmic electrode (5) was formed on the high electron concentration layer (2) to produce a Schottky element. Good Schottky characteristics with a reverse breakdown voltage of 840V were obtained. An IV characteristic is shown in FIG.
[0029]
The present invention is not limited to the above embodiment. For example, the present invention includes a case where a thin insulating layer is formed on 3C-SiC unintentionally.
[0030]
In addition, various modifications can be made without departing from the spirit of the present invention.
[0031]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a semiconductor element including a 3C—SiC crystal having good Schottky characteristics and a method for manufacturing the same.
[Brief description of the drawings]
FIG. 1 is a process cross-sectional view illustrating a method for manufacturing a 3C—SiC Schottky element according to a first embodiment of the present invention.
FIG. 2 is a process cross-sectional view subsequent to FIG. 1;
FIG. 3 is a process cross-sectional view showing a conventional method for manufacturing a 3C-SiC Schottky element.
4 is a process cross-sectional view subsequent to FIG. 3. FIG.
FIG. 5 is a characteristic diagram showing current-voltage characteristics of the Schottky element of the present invention (a) and the conventional example (b).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Si substrate 2 ... High electron concentration 3C-SiC layer 3 ... Low electron concentration 3C-SiC layer 3a ... Silicon oxide film 4 ... Schottky electrode 5 ... Ohmic electrode 101 ... Si substrate 102 ... High electron concentration 3C-SiC layer 103 ... Low electron concentration 3C-SiC layer 104 ... Schottky electrode 105 ... Ohmic electrode

Claims (8)

A substrate having a SiC region having a 3C-type crystal structure formed on the surface, a metal layer forming a Schottky junction with the SiC region, and an electric current from the metal layer interposed between the SiC region and the metal layer. A semiconductor device comprising an insulating thin film containing Si as a constituent element, which enables implantation. _2. The semiconductor device according to claim 1, wherein the thin film is made of SiO2. The semiconductor element according to claim 2, wherein the thin film has a thickness of 1 nm to 5 nm. A substrate having a SiC region having a 3C-type crystal structure formed on the surface, a metal layer forming a Schottky junction with the SiC region, and an electric current from the metal layer interposed between the SiC region and the metal layer. A method of manufacturing a semiconductor device including an insulating thin film containing Si as a constituent element, which enables implantation, wherein ions are implanted into a SiC region having a 3C-type crystal structure to thereby form the insulating thin film on the region. A method for manufacturing a semiconductor device, characterized in that: A substrate having a SiC region having a 3C-type crystal structure formed on the surface, a metal layer forming a Schottky junction with the SiC region, and an electric current from the metal layer interposed between the SiC region and the metal layer. A method of manufacturing a semiconductor device comprising an insulating thin film containing Si as a constituent element that enables implantation, and etching the SiC region having a 3C-type crystal structure with a solution to form the insulating thin film on the region A method for manufacturing a semiconductor device, characterized in that: A substrate having a SiC region having a 3C-type crystal structure formed on the surface, a metal layer forming a Schottky junction with the SiC region, and an electric current from the metal layer interposed between the SiC region and the metal layer. A method of manufacturing a semiconductor device including an insulating thin film containing Si as a constituent element that enables implantation, and forming the insulating thin film on a SiC region having a 3C-type crystal structure by vapor deposition A method for manufacturing a semiconductor device. A substrate having a SiC region having a 3C-type crystal structure formed on the surface, a metal layer forming a Schottky junction with the SiC region, and an electric current from the metal layer interposed between the SiC region and the metal layer. A method of manufacturing a semiconductor device including an insulating thin film containing Si as a constituent element that enables implantation, wherein a SiC region having a 3C-type crystal structure is left in the atmosphere for 5 days or more to be formed on the region. A method of manufacturing a semiconductor device, characterized by producing the insulating thin film. The method according to any one of claims 4 to 7, characterized in that to form a thin film made of SiO ₂ as the thin film.

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