JP2002026341A - Semiconductor device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device which is has low ON-resistance and a small leakage current and a method of manufacturing the same. SOLUTION: A semiconductor device is equipped with a board with a first semiconductor layer 2 provided with projections on its surface, an electrode layer 4 formed of metal material having lower thermal conductivity than semiconductor material that forms the first semiconductor layer 2, and an alloy layer 5 of alloy of the component material of the first semiconductor layer 2 and the component material of the electrode layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, to a semiconductor device using a semiconductor material such as SiC and a method of manufacturing the same.

[0002]

2. Description of the Related Art A semiconductor element such as a Schottky barrier diode using SiC as a semiconductor material has a problem that the Schottky barrier is high and the on-resistance of the element is high due to the wide band gap of SiC. There is also a problem that the leakage current at the time of off is large.

On the other hand, in a semiconductor element such as a Schottky barrier diode, it is indispensable to form an electrode exhibiting Schottky characteristics on the surface of a semiconductor substrate. However, an ohmic characteristic is exhibited for the purpose of improving the element characteristics. There are cases where it is desired to form electrodes and the like on the surface of a common semiconductor substrate.

[0004] However, in such a case,
If an electrode exhibiting Schottky characteristics and an electrode exhibiting ohmic characteristics are to be manufactured in separate steps, the number of steps increases, and the yield of element production deteriorates.

[0005]

SUMMARY OF THE INVENTION As described above, SiC
It is desired to reduce the on-resistance of semiconductor elements, particularly Schottky barrier diodes, and to suppress leakage current. Also,
In a case where an electrode exhibiting Schottky characteristics and an electrode exhibiting ohmic characteristics are manufactured in separate steps in a semiconductor element, there is a problem that the number of steps is increased and the yield of element manufacturing is deteriorated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor device having low on-resistance and low leakage current, and to manufacture the device by a simple process.

[0007]

A semiconductor device according to the present invention includes a substrate having a first semiconductor layer having a convex portion formed on a surface thereof, a substrate formed on the first semiconductor layer, An electrode layer made of a metal material having a lower thermal conductivity than the semiconductor material of the semiconductor layer, and a constituent material of the first semiconductor layer and a constituent material of the electrode layer selectively formed in an upper region of the protrusion. And an alloy layer made of the alloy of (1).

According to a method of manufacturing a semiconductor device according to the present invention, an electrode made of a metal material having a lower thermal conductivity than the semiconductor material of the first semiconductor layer is formed on the first semiconductor layer having a convex portion formed on the surface. Forming a layer, and selectively irradiating the electrode layer on the protrusion with an energy beam, and forming a material of the first semiconductor layer and a material of the electrode layer on an upper region of the protrusion. Selectively forming an alloy layer made of an alloy of
It is characterized by having.

According to the present invention, in the portion where the electrode layer is in contact with the first semiconductor layer, the Schottky barrier of the Schottky junction is high and the contact resistance is high. The portion where the layers are in contact has a lower Schottky barrier and lower contact resistance than the portion where the electrode layer is in contact with the first semiconductor layer. Therefore, in the on state, current mainly flows through a low-resistance region where the first semiconductor layer and the alloy layer are in contact with each other. on the other hand,
In the off state, the depletion layers extending from the side surfaces of the projections of the first semiconductor layer are connected to each other, so that a current path is cut off and a leakage current can be reduced. With such an operation, a semiconductor device having low on-resistance and low leakage current can be obtained.

Further, by using a metal material having a lower thermal conductivity than the semiconductor material of the first semiconductor layer for the electrode layer,
When the energy beam is selectively irradiated on the electrode layer on the protrusion, the first semiconductor layer efficiently removes heat from the electrode layer, so that only the intended region can be selectively heated,
An alloy layer can be accurately formed in a desired region.

A semiconductor device according to the present invention comprises a substrate having a first semiconductor layer of a first conductivity type, and a second conductivity type selectively formed in a part of a surface region of the first semiconductor layer. Second
And an electrode layer formed on the first and second semiconductor layers and made of a metal material having a lower thermal conductivity than the semiconductor material of the second semiconductor layer; An alloy layer selectively formed on at least a part of the surface region and made of an alloy of the constituent material of the second semiconductor layer and the constituent material of the electrode layer is provided.

The method of manufacturing a semiconductor device according to the present invention is directed to a method of manufacturing a semiconductor device of the second conductivity type selectively formed on the first semiconductor layer of the first conductivity type and in a part of the surface region of the first semiconductor layer. Forming an electrode layer made of a metal material having a lower thermal conductivity than the semiconductor material of the second semiconductor layer on the second semiconductor layer; and selectively forming energy on the electrode layer on the second semiconductor layer. Irradiating a line to selectively form an alloy layer made of an alloy of a constituent material of the second semiconductor layer and a constituent material of the electrode layer on at least a part of a surface region of the second semiconductor layer. And the following.

According to the present invention, by using a metal material having a lower thermal conductivity than the semiconductor material of the first or second semiconductor layer for the electrode layer, the energy layer can be selectively applied to the electrode layer on the semiconductor layer. Is irradiated, the second semiconductor layer efficiently removes heat from the electrode layer, so that only the intended region can be selectively heated, and the alloy layer can be accurately formed in the desired region. it can.

When the semiconductor device of the present invention is used in, for example, a Schottky barrier diode, a current flows through a Schottky junction in a portion where the electrode layer is in contact with the first semiconductor layer in an ON state. On the other hand, in the off state, a depletion layer is formed by a pn junction between the first semiconductor layer and the second semiconductor layer, and a current path is cut off, so that leakage current is reduced. Since the current is cut off by the depletion layer of the pn junction, the Schottky barrier of the Schottky junction between the first semiconductor layer and the electrode layer does not need to be high. Therefore, a material having a small work function can be used for the electrode layer, and the on-resistance can be reduced by a low Schottky barrier. By such an action,
A semiconductor device with low on-resistance and low leakage current can be obtained.

The semiconductor material of the first and second semiconductor layers may be SiC, diamond or GaN. Examples of the metal material of the electrode layer include Ti, Ni or Mo, or a laminated film or an alloy film made of at least two kinds of the metal group. In addition, a laser can be used as the energy ray.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a view showing an example of a manufacturing process of a semiconductor device (Schottky barrier diode) according to a first embodiment of the present invention.

As shown in FIG. 1C, an n ^-- SiC layer 2 is formed on an n ⁺ -SiC substrate 1 in a layer shape.
on the back surface of the n ⁺ -SiC substrate 1 n ⁺ -SiC substrate 1 and the cathode electrode 3 in ohmic junction is formed. n
^- on the surface of -SiC layer 2 has a plurality of irregularities are formed, n the irregularities are formed ^- on -SiC layer 2 the n ^-
Anode electrode 4 Schottky-bonded to SiC layer 2
Are formed. Between the upper surface of the convex portion of the n ⁻ -SiC layer 2 and the anode electrode 4, the metal material used for the anode electrode 4 and the material (at least one of Si and C) constituting the n ⁻ −SiC layer 2 are mixed. An alloy region 5 made of an alloy is formed. The anode electrode 4 is made of a metal having a lower thermal conductivity than SiC, for example, Ti, Ni or Mo, or
It is possible to use a laminated film or an alloy film made of at least two kinds of the metal group.

Hereinafter, the manufacturing process of this embodiment will be described with reference to FIGS. 1 (a) to 1 (c).

First, as shown in FIG. 1A, n ⁺ -S
After forming the n ⁻ -SiC layer 2 on the iC substrate 1 in a layered form,
The surface of the n ⁻ -SiC layer 2 is processed to form irregularities. Then, after the cathode electrode 3 was formed by vapor deposition or the like on the rear surface of the n ⁺ -SiC substrate 1, the cathode electrode 3 is n ⁺ -Si
Sintering is performed on the C substrate 1 so as to exhibit ohmic characteristics. Thereafter, the anode electrode 4 is formed on the n ⁻ -SiC layer 2 on which the irregularities are formed. As a material of the anode electrode 4, a metal having lower thermal conductivity than SiC, for example, Ti,
Ni or Mo, or at least two members of the metal group
A laminated film or an alloy film of various types is used.

Next, as shown in FIG. 1B, n ⁻ −S
By selectively irradiating the laser to the anode electrode 4 on the region corresponding to the convex portion of the iC layer 2, the alloy region 5 and the n ⁻ -SiC layer 2 are formed as shown in FIG. And is selectively formed in the region between.

Next, the element characteristics of the semiconductor device according to this embodiment will be described. The portion where the anode electrode 4 and the n ⁻ -SiC layer 2 are in direct contact is a Schottky junction, and has a high contact resistance due to a high Schottky barrier. On the other hand, the interface between the alloy region 5 and the n ⁻ -SiC layer 2 has a reduced barrier height due to the laser irradiation effect, and a low contact resistance is obtained. Therefore, when the diode is in the on state, an on current mainly flows through alloy region 5, and when the diode is in the off state, depletion layers extending from both side surfaces of the convex portion of n ⁻ -SiC layer 2 are connected to each other, thereby interrupting the current path. . By such an operation, the on-resistance can be reduced while the breakdown voltage of the element is high and the leak current is reduced.

In order to obtain the above-described functions and effects,
As a material of the anode electrode 4, it is important to use a metal having lower thermal conductivity than SiC, for example, Ti, Ni or Mo, or a laminated film or an alloy film made of at least two kinds of the above-mentioned metal group. Although the laser irradiation part of the anode electrode 4 is heated by the laser irradiation, the anode electrode 4 is heated.
Since the n ⁻ -SiC layer 2 having a higher thermal conductivity is in contact with the anode electrode 4, the SiC deprives the anode electrode 4 of heat and raises the temperature of the anode electrode 4 over a wider range than the laser irradiation part. Can be prevented. If the temperature rises in a wider range than the laser-irradiated portion, the alloy region 5 may be formed in an area other than the upper part of the projection, and desired characteristics may not be obtained.

In the example described above, as shown in FIG. 1C, the anode electrode 4 and the n ^-- S
Although the alloy region 5 is formed between the iC layer 2 and the iC layer 2,
Anode electrode 4 formed on the projection of n ⁻ -SiC layer 2
The whole may be converted to the alloy region 5. In this case, it is preferable to further form a metal film on anode electrode 4 and alloy region 5 after the laser irradiation step.

(Second Embodiment) FIG. 2 is a view showing an example of a manufacturing process of a semiconductor device (Schottky barrier diode) according to a second embodiment of the present invention.

As shown in FIG. 2C, an n ⁻ -SiC layer 2 is formed in a layer on an n ⁺ -SiC substrate 1.
on the back surface of the n ⁺ -SiC substrate 1 n ⁺ -SiC substrate 1 and the cathode electrode 3 in ohmic junction is formed. n
^- the surface area of the -SiC layer 2 islands to the plurality of p-SiC
A layer 6 is formed, and the n ⁻ -SiC layer 2 and the p-Si
On the C layer 6, an anode electrode 4 which is Schottky-bonded with the n ⁻ -SiC layer 2 is formed. Between the p-SiC layer 6 and the anode electrode 4, an alloy region 5 made of an alloy of the metal material used for the anode electrode 4 and the material (at least one of Si and C) constituting the p-SiC layer 6 is formed. The interface between the alloy region 5 and the p-SiC layer 6 is an ohmic junction. The anode electrode 4 has S
A metal having a lower thermal conductivity than iC, for example, Ti, Ni or Mo, or a laminated film or an alloy film made of at least two kinds of the above-described metal group can be used.

Hereinafter, the manufacturing process of this embodiment will be described with reference to FIGS. 2 (a) to 2 (c).

First, as shown in FIG. 2A, n ⁺ -S
After forming the n ⁻ -SiC layer 2 on the iC substrate 1 in a layered form,
A p-SiC layer 6 is formed in an island shape on the surface region of n ⁻ -SiC layer 2. Subsequently, after the cathode electrode 3 is formed on the back surface of the n ⁺ -SiC substrate 1 by vapor deposition or the like, the cathode electrode 3 is formed.
Is applied to the n ⁺ -SiC substrate 1 so as to exhibit ohmic characteristics. Then, the n ⁻ -SiC layer 2 and p
Forming the anode electrode 4 on the SiC layer 6; As a material of the anode electrode 4, a metal having a lower thermal conductivity than SiC, for example, Ti, Ni or Mo, or a laminated film or an alloy film composed of at least two kinds of the above-mentioned metal group is used.

Next, as shown in FIG.
By selectively irradiating the laser to the anode electrode 4 on a region corresponding to the inside of the region where the C layer 6 is formed, as shown in FIG. It is selectively formed in a region between SiC layer 6.

Next, the element characteristics of the semiconductor device according to this embodiment will be described. A portion where the anode electrode 4 and the n ⁻ -SiC layer 2 are in direct contact is a Schottky junction, and a current flows through the Schottky junction when the diode is on. In the off state, p-
Since a depletion layer is formed at the pn junction interface between the SiC layer 6 and the n ⁻ -SiC layer 2 and pinch-off occurs due to the pn junction, the leak current is greatly reduced. In order to obtain such an effect, it is necessary to exhibit ohmic characteristics between the p-SiC layer 6 and the electrode. However, the interface between the alloy region 5 and the p-SiC layer 6 is low-resistance ohmic junction by laser irradiation. It has become. Further, as described above, since the current can be interrupted by pinch-off, it is not necessary to increase the Schottky barrier at the interface between the anode electrode 4 and the n ⁻ -SiC layer 2. Therefore, by selecting a material having a small work function as the material of the anode electrode 4, a low Schottky barrier can be formed and the on-resistance can be reduced. That is, it is possible to reduce the leak current and the on-voltage.

In order to obtain the above-described functions and effects,
As a material of the anode electrode 4, it is important to use a metal having lower thermal conductivity than SiC, for example, Ti, Ni or Mo, or a laminated film or an alloy film made of at least two kinds of the above-mentioned metal group. Although the laser irradiation part of the anode electrode 4 is heated by the laser irradiation, the anode electrode 4 is heated.
P-SiC layer 6 having a higher thermal conductivity than anode electrode 4
, The SiC deprives the anode electrode 4 of heat and prevents the temperature of the anode electrode 4 from rising over a wider area than the laser-irradiated portion. Therefore, the alloy region 5 can be accurately formed in a desired region.

In the above example, as shown in FIG. 2C, the anode electrode 4 and the p-Si
Although the alloy region 5 is formed between the alloy region 5 and the C layer 6, the entire anode electrode 4 in the region irradiated with the laser is
May be converted to In this case, it is preferable to further form a metal film on anode electrode 4 and alloy region 5 after the laser irradiation step.

(Third Embodiment) FIG. 3 is a view showing an example of a manufacturing process of a semiconductor device (Schottky barrier diode) according to a second embodiment of the present invention. The basic structure, manufacturing method, and element characteristics are the same as those of the second embodiment shown in FIG. 2, and therefore, detailed description thereof is omitted here.

In this embodiment, a SiO ₂ film (silicon oxide film) 11 is formed on a part of the n ⁻ -SiC layer 2, and the terminal portion of the anode electrode 4 runs over the SiO ₂ film 11. It has become. Thus, by providing the SiO ₂ film 11 at the terminal portion of the anode electrode 4,
The concentration of the electric field at the terminal of the electrode is reduced, and the withstand voltage can be increased.

(Fourth Embodiment) FIG. 4 is a view showing an example of a manufacturing process of a semiconductor device (Schottky barrier diode) according to a fourth embodiment of the present invention. The basic structure, manufacturing method, and element characteristics are the same as those of the second embodiment shown in FIG. 2, and therefore, detailed description thereof is omitted here.

In this embodiment, a SiO ₂ film (silicon oxide film) 11 is formed on a part of the n ⁻ -SiC layer 2, and the terminal portion of the anode electrode 4 runs over the SiO ₂ film 11. It has become. Further, a p ⁺ -SiC layer 22 is provided below a portion where the anode electrode 4 is in contact with the SiO ₂ film 11.
There are formed, a lower carrier concentration than the p ⁺ -SiC layer 22 so as to surround the p ⁺ -SiC layer 22 p-
An SiC layer 21 is formed.

As shown in FIGS. 4A and 4B, p-
The SiC layer 21 is formed simultaneously with or separately from the p-SiC layer 6, and the p ⁺ -SiC layer 22 is formed by selectively irradiating a part of the p-SiC layer 21 with laser. p
-SiC layer 21 is produced by, for example, an ion implantation method,
By selectively irradiating laser after ion implantation,
P-SiC layer 21 and p ⁺ -SiC layer 2 having different activation rates
2 can be easily obtained.

In the present embodiment, the third embodiment shown in FIG.
In addition to the same effects as those of the embodiment, the SiO ₂ film 11
By providing the p ⁺ -SiC layer 22 and the p-SiC layer 21 below, the concentration of the electric field at the terminal of the electrode can be further reduced, and the withstand voltage can be further increased.

The matters described in the third and fourth embodiments described above are similarly applicable to the semiconductor device shown in the first embodiment.

In the first to fourth embodiments, the laser has a spot size φ of 0.5 to 20 μm.
It is preferable to use a KrF excimer laser or the like having a power of 0.5 to 5 J / cm ² at m. By adjusting the laser power or adjusting the number of irradiation pulses by making the laser pulse-like, it is possible to appropriately adjust the contact resistance value, the on-resistance value, the leak current value, and the like between the alloy region and the SiC interface.

In the first to fourth embodiments described above, 2H, 4H, 6H, 15R, 3C
The above applies to SiC having all crystal structures. Also,
In the above-described first to fourth embodiments, SiC has been described as an example, but the present invention is also applicable to devices using semiconductor materials such as diamond and GaN. In particular, diamond is a semiconductor material suitable for the present invention because of its high thermal conductivity.

Further, in the above-described first to fourth embodiments, the Schottky barrier diode has been described as an example. However, the present invention can be applied to other rectifying elements and switching elements having a Schottky barrier.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be variously modified and implemented without departing from the gist thereof. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining the disclosed constituent elements. For example, even if some constituent elements are deleted from the disclosed constituent elements, they can be extracted as an invention as long as a predetermined effect can be obtained.

[0044]

According to the present invention, it is possible to obtain a semiconductor device having low on-resistance and low leakage current.

[Brief description of the drawings]

FIG. 1 is a process sectional view showing a manufacturing process of a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a process sectional view showing a manufacturing process of a semiconductor device according to a second embodiment of the present invention.

FIG. 3 is a process sectional view showing a manufacturing process of a semiconductor device according to a third embodiment of the present invention.

FIG. 4 is a process sectional view showing a manufacturing process of a semiconductor device according to a fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... n ^<+ > ^- SiC substrate 2 ... n < ^- > ^- SiC layer (1st semiconductor layer) 3 ... Cathode electrode 4 ... Anode electrode (electrode layer) 5 ... Alloy region (alloy layer) 6 ... p-SiC layer (2nd 11 ... SiO ₂ film 21 ... p-SiC layer 22 ... p ⁺ -SiC layer

Continued on the front page (72) Inventor Takashi Yonohe 1-term, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term in the Toshiba R & D Center (reference) 4M104 AA04 AA10 BB05 BB14 BB16 CC01 CC03 DD78 DD81 DD83 FF35 GG03 HH18 HH20

Claims (6)

[Claims] A substrate having a first semiconductor layer having a convex portion formed on a surface thereof; a substrate formed on the first semiconductor layer and having a lower thermal conductivity than a semiconductor material of the first semiconductor layer. An electrode layer made of a metal material; and an alloy layer selectively formed in an upper region of the convex portion and made of an alloy of a constituent material of the first semiconductor layer and a constituent material of the electrode layer. A semiconductor device characterized by the above-mentioned. 2. A substrate having a first semiconductor layer of a first conductivity type, and a second semiconductor layer of a second conductivity type selectively formed in a part of a surface region of the first semiconductor layer. An electrode layer formed on the first and second semiconductor layers and made of a metal material having a lower thermal conductivity than the semiconductor material of the second semiconductor layer; and at least a surface region of the second semiconductor layer. A semiconductor device, comprising: an alloy layer formed selectively on a part thereof and made of an alloy of a constituent material of the second semiconductor layer and a constituent material of the electrode layer. 3. The semiconductor device according to claim 1, wherein a semiconductor material of the first and second semiconductor layers is SiC, diamond, or GaN. 4. The semiconductor device according to claim 1, wherein said electrode layer is an anode electrode of a Schottky barrier diode. 5. A step of forming an electrode layer made of a metal material having a lower thermal conductivity than a semiconductor material of the first semiconductor layer on the first semiconductor layer having a projection formed on a surface thereof; Selectively irradiating the electrode layer on the portion with an energy beam to selectively form an alloy layer made of an alloy of the constituent material of the first semiconductor layer and the constituent material of the electrode layer in the upper region of the protrusion. A method of manufacturing a semiconductor device, comprising: 6. A second conductive type second semiconductor layer selectively formed on a first conductive type first semiconductor layer and a part of a surface region of the first semiconductor layer. Forming an electrode layer made of a metal material having a lower thermal conductivity than the semiconductor material of the semiconductor layer; and selectively irradiating the electrode layer on the second semiconductor layer with energy rays, Selectively forming an alloy layer made of an alloy of the constituent material of the second semiconductor layer and the constituent material of the electrode layer on at least a part of the surface region of the semiconductor layer. A method for manufacturing a semiconductor device.