JP3523156B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly to a semiconductor device using a semiconductor material such as SiC and a manufacturing method thereof.

[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 because the forbidden band width of SiC is wide. There is also a problem that there is a large amount of leakage current when turned off.

On the other hand, in such a semiconductor element such as a Schottky barrier diode, it is indispensable to form an electrode exhibiting the Schottky characteristic on the surface of the semiconductor substrate, but it exhibits ohmic characteristics 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.

However, in such a case,
If the electrode exhibiting the Schottky characteristic and the electrode exhibiting the ohmic characteristic are manufactured in separate steps, the number of steps increases and the yield of manufacturing the device also deteriorates.

[0005]

SUMMARY OF THE INVENTION As described above, SiC
There is a demand for reduction of on-resistance and suppression of leakage current of semiconductor elements, especially Schottky barrier diodes. Also,
In the case of manufacturing an electrode having a Schottky characteristic and an electrode having an ohmic characteristic in a semiconductor element in separate steps, there is a problem in that the number of steps increases and the yield of element production also deteriorates.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a semiconductor device having a low on-resistance and a small 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 the surface thereof, and the first semiconductor layer formed on the substrate. An electrode layer made of a metal material having a thermal conductivity lower than that of the semiconductor material of the semiconductor layer, and a constituent material of the first semiconductor layer and a constituent material of the electrode layer which are selectively formed in an upper region of the convex portion. And an alloy layer made of the alloy of.

In the method for 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 its surface. A step of forming a layer, and selectively irradiating the electrode layer on the convex portion with an energy beam to form a constituent material of the first semiconductor layer and a constituent material of the electrode layer in an upper region of the convex portion. Selectively forming an alloy layer composed of the 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 Schottky barrier is lower in the portion where the layers are in contact with each other and the contact resistance is lower than that in the portion where the electrode layer is in contact with the first semiconductor layer. Therefore, in the on-state, a current mainly flows through the 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, since the depletion layers extending from the side surface of the convex portion of the first semiconductor layer are connected to each other, the current path is interrupted and the leak current can be reduced. With such an action, it is possible to obtain a semiconductor device having a low on-resistance and a small leak current.

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 electrode layer on the convex portion is selectively irradiated with energy rays, the first semiconductor layer efficiently removes heat from the electrode layer, so that only the intended region can be selectively heated,
The alloy layer can be accurately formed in the 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
A 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 the second semiconductor layer. An alloy layer, which is selectively formed in at least a part of the surface region and is made of an alloy of the constituent material of the second semiconductor layer and the constituent material of the electrode layer, is provided.

A method of manufacturing a semiconductor device according to the present invention comprises a second conductivity type first semiconductor layer selectively formed on a first conductivity type first semiconductor layer and a part of a surface region of the first semiconductor layer. A step of forming an electrode layer made of a metal material having a thermal conductivity lower than that of the semiconductor material of the second semiconductor layer on the second semiconductor layer, and selectively applying energy to the electrode layer on the second semiconductor layer. Irradiating a line to selectively form 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 second semiconductor layer. And are included.

According to the present invention, by using a metal material whose thermal conductivity is lower than that of the semiconductor material of the first or second semiconductor layer for the electrode layer, the energy beam is selectively applied to the electrode layer on the semiconductor layer. The second semiconductor layer efficiently removes heat from the electrode layer when irradiated with, 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, in the ON state, a current flows through the Schottky junction at the portion where the electrode layer is in contact with the first semiconductor layer. On the other hand, in the off state, the depletion layer is formed by the pn junction between the first semiconductor layer and the second semiconductor layer and the current path is cut off, so that the leak current is reduced. Since the current is blocked by the depletion layer of the pn junction in this manner, the Schottky barrier of the Schottky junction between the first semiconductor layer and the electrode layer does not have to be high. Therefore, a material having a low work function can be used for the electrode layer, and the low Schottky barrier can reduce the on-resistance. By such action,
It is possible to obtain a semiconductor device having a low on-resistance and a small leak current.

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

[0016]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a diagram 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. 1 (c), an n ^-- SiC layer 2 is formed in layers 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
^- 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 in Schottky junction with SiC layer 2
Are formed. Between the upper surface of the convex portion of the n ^-- SiC layer 2 and the anode electrode 4, a metal material used for the anode electrode 4 and a material (at least one of Si and C) forming the n ^-- SiC layer 2 are provided. An alloy region 5 made of an alloy is formed. For the anode electrode 4, a metal having a lower thermal conductivity than SiC, such as Ti, Ni or Mo, or
It is possible to use a laminated film or an alloy film composed of at least two kinds of the metal group.

The manufacturing process of this embodiment will be described below with reference to FIGS. 1 (a) to 1 (c).

First, as shown in FIG. 1A, n ⁺ -S
After the n ⁻ -SiC layer 2 is formed in layers on the iC substrate 1,
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
Sinter is applied to the C substrate 1 so as to exhibit ohmic characteristics. Then, the anode electrode 4 is formed on the n ⁻ -SiC layer 2 having the irregularities. As a material of the anode electrode 4, a metal having a lower thermal conductivity than SiC, for example, Ti,
Ni or Mo, or at least 2 of the above metal groups
A laminated film or an alloy film of different types is used.

Next, as shown in FIG. 1B, n ^-- S
By selectively irradiating the anode electrode 4 on the region corresponding to the convex portion of the iC layer 2 with a laser, as shown in FIG. 1 (c), the alloy region 5 and the anode electrode 4 and the n ^-- SiC layer 2 are formed. Is selectively formed in a region between and.

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 the contact resistance is high because the Schottky barrier is high. On the other hand, at the interface between the alloy region 5 and the n ⁻ -SiC layer 2, the height of the barrier is reduced by the laser irradiation effect, and a low contact resistance is obtained. Therefore, when the diode is in the on-state, the on-current mainly flows through the alloy region 5, and when it is in the off-state, the depletion layers extending from both side surfaces of the convex portion of the n ^-- SiC layer 2 are connected to each other to interrupt the current path. . By such an action, the on-resistance can be reduced while increasing the breakdown voltage of the element and reducing the leak current.

In order to obtain the above-mentioned effects,
As the material of the anode electrode 4, it is important to use a metal having a 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 metal group. The laser irradiation heats the laser-irradiated portion of the anode electrode 4.
Since the n ^-- SiC layer 2 having a higher thermal conductivity than the anode electrode 4 is in contact with the anode electrode 4, SiC absorbs heat of the anode electrode 4 and the temperature of the anode electrode 4 rises in a wider range than the laser irradiation portion. Can be prevented. If the temperature rises in a wider range than the laser-irradiated portion, the alloy region 5 may be formed in areas other than the upper portion of the convex portion, and desired characteristics may not be obtained.

[0024] In the example described above, as shown in FIG. 1 (c), the anode electrode 4 by the laser irradiation and ⁿ - -S
Although the alloy region 5 is formed between the iC layer 2 and
Anode electrode 4 formed on the convex portion of the n ^-- SiC layer 2
The whole may be converted into the alloy region 5. In this case, it is preferable to further form a metal film on the anode electrode 4 and the alloy region 5 after the laser irradiation step.

(Second Embodiment) FIG. 2 is a diagram 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. 2 (c), an n ^-- SiC layer 2 is formed in layers on the 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
The layer 6 is formed, and the n ^-- SiC layer 2 and p-Si are formed.
An anode electrode 4 is formed on the C layer 6 in Schottky contact with the n ^-- SiC layer 2. Between the p-SiC layer 6 and the anode electrode 4, an alloy region 5 made of an alloy of a metal material used for the anode electrode 4 and a material forming the p-SiC layer 6 (at least one of Si and C) is provided. It is formed, and 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 metal group can be used.

The manufacturing process of this embodiment will be described below with reference to FIGS. 2 (a) to 2 (c).

First, as shown in FIG. 2A, n ⁺ -S
After the n ⁻ -SiC layer 2 is formed in layers on the iC substrate 1,
The p-SiC layer 6 is formed in an island shape in the surface region of the 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.
Sinters the n ⁺ -SiC substrate 1 so as to exhibit ohmic characteristics. Then, the n ^-- SiC layer 2 and p
-Anode electrode 4 is formed on SiC layer 6. As the 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 made of at least two kinds of the above metal group is used.

Next, as shown in FIG. 2B, p-Si
By selectively irradiating the anode electrode 4 on the region corresponding to the inner side of the region where the C layer 6 is formed with the laser, the alloy region 5 and the anode electrode 4 and p- are formed as shown in FIG. 2C. 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. The portion where the anode electrode 4 and the n ^-- SiC layer 2 are in direct contact is a Schottky junction, and when the diode is in the on state, a current flows through the Schottky junction portion. When off, p-
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, so that the leak current is significantly reduced. In order to obtain such an action, it is necessary to exhibit ohmic characteristics between the p-SiC layer 6 and the electrode, but the interface between the alloy region 5 and the p-SiC layer 6 is low resistance ohmic junction by laser irradiation. Has become. Further, as described above, since the current can be cut off 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, it is possible to form a low Schottky barrier and reduce the on-resistance. That is, it is possible to reduce the leak current and the on-voltage.

In order to obtain the above-mentioned effects,
As the material of the anode electrode 4, it is important to use a metal having a 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 metal group. The laser irradiation heats the laser-irradiated portion of the anode electrode 4.
The p-SiC layer 6 having higher thermal conductivity than the anode electrode 4
Since it is in contact with, it is possible to prevent the heat of the anode electrode 4 from being taken by SiC and the temperature of the anode electrode 4 rising in a wider range than the laser irradiation portion. Therefore, the alloy region 5 can be accurately formed in the desired region.

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

(Third Embodiment) FIG. 3 is a diagram 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 device characteristics are the same as those of the second embodiment shown in FIG. 2, so detailed description thereof will be omitted here.

In the present embodiment, the SiO ₂ film (silicon oxide film) 11 is formed on a part of the n ⁻ -SiC layer 2, and the end portion of the anode electrode 4 rides on the SiO ₂ film 11. Has become. In this way, by providing the SiO ₂ film 11 at the end portion of the anode electrode 4,
The concentration of the electric field at the electrode termination is relaxed, and a high breakdown voltage can be achieved.

(Fourth Embodiment) FIG. 4 is a diagram 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 device characteristics are the same as those of the second embodiment shown in FIG. 2, so detailed description thereof will be omitted here.

In the present embodiment, the SiO ₂ film (silicon oxide film) 11 is formed on a part of the n ⁻ -SiC layer 2, and the end portion of the anode electrode 4 rides on the SiO ₂ film 11. Has become. Further, the p ⁺ -SiC layer 22 is formed below the 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-
The 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 a laser. p
-The 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.

Also in this embodiment, the third circuit shown in FIG.
In addition to obtaining the same effect as the embodiment described above, the SiO ₂ film 11
By providing the p ⁺ -SiC layer 22 and the p-SiC layer 21 below, the electric field concentration on the electrode termination can be further alleviated, and the breakdown voltage can be further increased.

The matters shown in the third and fourth embodiments described above can be similarly applied to the semiconductor device shown in the first embodiment.

In the above-described 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 m and a power of 0.5 to 5 J / cm ² . By adjusting the laser power or adjusting the irradiation pulse number by making the laser pulsed, it is possible to appropriately adjust the contact resistance value, on-resistance value, leak current value, etc. of the alloy region and the SiC interface.

Further, in the above-described first to fourth embodiments, the SiC is 2H, 4H, 6H, 15R, 3C.
Etc. SiC having all crystal structures is applicable. Also,
Although SiC has been described as an example in the above-described first to fourth embodiments, it can be applied to an element using a semiconductor material such as diamond or GaN. In particular, diamond is a semiconductor material suitable for the present invention because it has high thermal conductivity.

Furthermore, in the above-mentioned first to fourth embodiments, the Schottky barrier diode has been described as an example, but 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 embodiments, and various modifications can be carried out without departing from the spirit of the invention. Furthermore, the embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining the disclosed constituent features. For example, even if some constituents are deleted from the disclosed constituents, any invention 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 a low on-resistance and a small leakage current.

[Brief description of drawings]

FIG. 1 is a process cross-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 invention.

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

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

[Explanation of symbols]

1 ... n ⁺ -SiC substrate 2 ... ⁿ - -SiC layer (first semiconductor layer) 3 ... cathode electrode 4 ... anode electrode (electrode layer) 5 ... alloy regions (alloy layer) 6 ... p-SiC layer (second Semiconductor layer) 11 ... SiO ₂ film 21 ... p-SiC layer 22 ... p ⁺ -SiC layer

Continuation of front page (56) Reference JP-A-10-284436 (JP, A) JP-A-2000-252479 (JP, A) JP-A-4-127474 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 29/872 H01L 29/417 H01L 29/47 H01L 21/28 H01L 29/06 H01L 29/80 H01L 29/861 H01L 29/73 H01L 29/74

Claims (6)

(57) [Claims] 1. A substrate having a first semiconductor layer having a convex portion formed on a surface thereof, and a substrate having a thermal conductivity lower than that of a semiconductor material of the first semiconductor layer formed on 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 the constituent material of the first semiconductor layer and the constituent material of the electrode layer. A semiconductor device characterized by: 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 thermal conductivity lower than that of 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 selectively formed on a part of the second semiconductor layer and an alloy layer of the material of the electrode layer and the material of the electrode layer. 3. The semiconductor device according to claim 1, wherein the semiconductor material of the first and second semiconductor layers is SiC, diamond or GaN. 4. The semiconductor device according to claim 1, wherein the 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 thermal conductivity lower than that of the semiconductor material of the first semiconductor layer on the first semiconductor layer having a convex portion formed on the surface thereof, and the convex portion. Energy rays are selectively irradiated onto the electrode layers on the projections 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 layers in the upper region of the convex portion. A method of manufacturing a semiconductor device, comprising: 6. A second semiconductor layer of the second conductivity type selectively formed on the first semiconductor layer of the first conductivity type and a part of a surface region of the first semiconductor layer, and a second semiconductor layer of the second conductivity type. Forming an electrode layer made of a metal material having a lower thermal conductivity than that of the semiconductor material of the second semiconductor layer; and selectively irradiating the electrode layer on the second semiconductor layer with an energy beam, 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. Manufacturing method of semiconductor device.