JP5674366B2 - Schottky barrier diode and manufacturing method thereof - Google Patents

Description

  The present invention relates to a Schottky barrier diode and a method for manufacturing the same.

Conventionally, a Schottky barrier diode (SBD) using a Schottky barrier generated at this interface by bonding a semiconductor and a metal is known (see, for example, Patent Document 1).
This SBD preferably has a small voltage drop when a predetermined voltage is applied in the forward direction and a small leakage current when a predetermined voltage is applied in the reverse direction.

FIG. 8 is a cross-sectional view showing an example of a conventional trench structure type Schottky barrier diode (SBD). In this SBD 1, a trench 3 is formed on a surface (one main surface) 2 a of a silicon substrate (semiconductor substrate) 2. An insulating film 4 made of a silicon oxide film is formed on the inner surface of the trench 3, and a conductor 5 made of polycrystalline silicon is embedded in the trench 3, and the surface 2 a of the silicon substrate 2 and the insulating film 4 are formed. The uppermost surface 4 a and the upper surface 5 a of the conductor 5 are flush with each other, and a barrier metal layer 6 and an electrode metal layer 7 are laminated so as to cover the silicon substrate 2, the insulating film 4 and the conductor 5.
In the SBD 1, a trench 3 is formed on the surface 2 a of the silicon substrate 2, an insulating film 4 is formed on the inner surface of the trench 3, and a conductor 5 made of polycrystalline silicon is formed in the trench 3 surrounded by the insulating film 4. And the barrier metal layer 6 and the electrode metal layer 7 are laminated so as to cover the silicon substrate 2, the insulating film 4 and the conductor 5.

JP 2008-282839 A

  By the way, in the conventional SBD 1, the electrical characteristics are very sensitive to external stresses such as tensile stress and compressive stress from the electrode metal layer 7 or solder (not shown) formed thereon. For example, when an external stress is applied from the electrode metal layer 7 or the like to the bonding interface between the barrier metal layer 6 and the conductor 5, the thermal expansion coefficients of the barrier metal layer 6 and the conductor 5, the silicon substrate 2, and the insulating film 4. Due to the difference in thermal expansion coefficient, the external stress is concentrated near the upper surface of the sidewall of the trench 3, and as a result, the reverse current (IR) increases, and in the worst case, the silicon substrate 2 may be warped. There was a problem.

  The present invention has been made to solve the above-described problem, and even when an external stress generated from the electrode metal layer or the like acts on the bonding interface between the barrier metal layer and the conductor, the stress is applied to the barrier metal. Dispersion within the layer can alleviate the concentration of external stress near the upper surface of the sidewall of the trench, and therefore, the reverse current (IR) can be reduced, and a method for manufacturing the same. The purpose is to provide.

  As a result of intensive studies in order to solve the above problems, the inventor has formed a trench on one main surface of a semiconductor substrate, an insulating film is formed on the inner surface of the trench, and a conductor in the trench. Is embedded, a barrier metal layer is formed on the conductor, and an electrode metal layer is formed on the barrier metal layer, a part of the barrier metal layer on the conductor layer If a metal having a higher thermal expansion coefficient than that of the barrier metal layer is embedded in the region or a region including the vicinity thereof, even when a stress such as a tensile stress is generated in the electrode metal layer, the metal is embedded in the barrier metal layer. The applied metal disperses the stress such as tensile stress applied from the electrode metal layer to the barrier metal layer, thereby reducing the concentration of this stress near the upper surface of the trench sidewall, and as a result It found that the current (IR) is suppressed, and have completed the present invention.

That is, in the Schottky barrier diode according to claim 1 of the present invention, a trench is formed on one main surface of a semiconductor substrate, an insulating film is formed on the inner surface of the trench, and a conductor is embedded in the trench, In a Schottky barrier diode in which a barrier metal layer is formed on the conductor and an electrode metal layer is formed on the barrier metal layer, a part of the barrier metal layer on the conductor layer or the vicinity thereof A metal having a thermal expansion coefficient higher than that of the barrier metal layer is embedded in a region including the metal, and a lower end portion of the metal is embedded in the conductor .

  In this Schottky barrier diode, a metal having a higher thermal expansion coefficient than that of the barrier metal layer is embedded in a part of the barrier metal layer or a region including the vicinity thereof on the conductor layer. When a stress such as a generated tensile stress acts on the barrier metal layer, the metal disperses the stress applied from the electrode metal layer to the barrier metal layer, and this stress is reduced from being concentrated near the upper surface of the trench sidewall. . As a result, an increase in reverse current (IR) due to stress concentration near the upper surface of the trench sidewall is suppressed.

The Schottky barrier diode according to claim 2 is the Schottky barrier diode according to claim 1, wherein the composition of the metal is the same as that of the electrode metal layer.
In this Schottky barrier diode, since the metal composition is the same as that of the electrode metal layer, the thermal expansion coefficient of the metal embedded in the barrier metal layer and the electrode metal layer is the same, and the metal and the metal There is no risk of problems such as warping, cracking, and peeling due to the difference in coefficient of thermal expansion with the electrode metal layer.

The lower end of the front Symbol metal is embedded in the conductor.
In this Schottky barrier diode, bonding strength between the metal and the conductor is increased by embedding the lower end portion of the metal in the conductor. As a result, even when an external stress such as a tensile stress from the electrode metal layer is applied to the barrier metal layer, the barrier metal layer containing the metal is warped between the conductor and there is no possibility of causing problems such as peeling. .

Claim 3, wherein the Schottky barrier diode in claim 1 or 2, wherein the Schottky barrier diode, the upper surface of the conductive body, characterized in that it is a concave surface.
In this Schottky barrier diode, since the upper surface of the conductor is a concave surface, a concave surface having a shape similar to the concave surface is also formed on the upper surfaces of the barrier metal layer and the electrode metal layer laminated on the conductor. Therefore, this concave surface becomes a solder pool when solder or the like is joined to the electrode metal layer, and prevents a solder flow or the like at the time of solder joining.

5. The method of manufacturing a Schottky barrier diode according to claim 4 , wherein a trench is formed on one main surface of the semiconductor substrate, an insulating film is formed on the inner surface of the trench, and a conductor is formed in the trench in which the insulating film is formed. In the method for manufacturing a Schottky barrier diode, which is buried, a barrier metal layer is formed on the conductor, and an electrode metal layer is formed on the barrier metal layer , a recess is formed on the upper surface of the conductor, and the barrier metal layer Forming an opening by selectively removing the upper region of the recess , depositing a metal having a higher thermal expansion coefficient than the barrier metal layer in the recess and the opening, and on the metal and the barrier metal layer The electrode metal layer is formed.

In this Schottky barrier diode manufacturing method, an opening is formed by selectively removing a part of the barrier metal layer formed on the conductor or a region including the vicinity thereof on the conductor. And depositing a metal having a higher thermal expansion coefficient than the barrier metal layer.
Thereby, it becomes possible to deposit a metal having a higher coefficient of thermal expansion than the barrier metal layer with high accuracy at a predetermined position of the barrier metal layer.
Therefore, by burying a metal having a higher thermal expansion coefficient than that of the barrier metal layer in a part of the barrier metal layer or a region including the vicinity thereof on the conductor layer, the stress from the electrode metal layer is dispersed and the trench is It is possible to easily manufacture a Schottky barrier diode in which the concentration in the vicinity of the upper surface of the side wall is relaxed and an increase in reverse current (IR) due to the concentration of stress is suppressed.

In another method of manufacturing a Schottky barrier diode, a trench is formed on one main surface of a semiconductor substrate, an insulating film is formed on the inner surface of the trench, a conductor is embedded in the trench in which the insulating film is formed, In the method for manufacturing a Schottky barrier diode, in which a barrier metal layer is formed on a conductor and an electrode metal layer is formed on the barrier metal layer, a part of the barrier metal layer on the conductor or the vicinity thereof Forming an opening by selectively removing a region containing the metal, depositing a metal having a higher thermal expansion coefficient than the barrier metal layer in the opening and on the barrier metal layer, and forming the metal in the opening and on the barrier metal layer. An electrode metal layer made of is formed.

In this Schottky barrier diode manufacturing method, an opening is formed by selectively removing a part of the barrier metal layer formed on the conductor or a region including the vicinity thereof on the conductor. A metal having a higher thermal expansion coefficient than that of the barrier metal layer is deposited on the barrier metal layer, and an electrode metal layer made of the metal is formed in the opening and on the barrier metal layer.
This makes it possible to accurately form an electrode metal layer made of a metal having a higher thermal expansion coefficient than the barrier metal layer in the opening of the barrier metal layer and on the barrier metal layer.
Therefore, by forming an electrode metal layer made of a metal having a higher thermal expansion coefficient than that of the barrier metal layer in the opening of the barrier metal layer and on the barrier metal layer, the stress from the electrode metal layer is dispersed and the trench It is possible to easily manufacture a Schottky barrier diode in which the concentration near the upper surface of the side wall is relaxed and an increase in reverse current (IR) due to the concentration of stress is suppressed.

  According to the Schottky barrier diode according to claim 1 of the present invention, a metal having a higher thermal expansion coefficient than the barrier metal layer is applied to a part of the barrier metal layer or a region including the vicinity thereof on the conductor layer. Even when a stress such as a tensile stress generated in the electrode metal layer acts on the barrier metal layer because it has been embedded, the metal embedded in the barrier metal layer disperses the stress, so that the stress is Concentration in the vicinity can be eased. Therefore, an increase in reverse current (IR) due to concentration of stress near the upper surface of the sidewall of the trench can be suppressed.

  According to the Schottky barrier diode according to claim 2, since the composition of the metal having a higher thermal expansion coefficient than that of the barrier metal layer is the same as that of the electrode metal layer, the metal embedded in the barrier metal layer, the electrode metal layer, The coefficient of thermal expansion of each other is the same, and problems such as warpage, cracking, and peeling between the metal embedded in the barrier metal layer and the electrode metal layer can be prevented.

  According to the Schottky barrier diode of claim 3, since the lower end portion of the metal having a higher coefficient of thermal expansion than the barrier metal layer is embedded in the conductor, the bonding strength between the metal and the conductor can be increased. Problems such as warpage and peeling between the barrier metal layer containing the metal and the conductor can be prevented.

  According to the Schottky barrier diode of the fourth aspect, since the upper surface of the conductor is a concave surface, a concave surface having a shape similar to the concave surface is also formed on the upper surfaces of the barrier metal layer and the electrode metal layer laminated on the conductor. By forming this concave surface as a solder pool when solder or the like is joined to the electrode metal layer, it is possible to prevent solder flow or the like during solder joining.

  According to the method of manufacturing a Schottky barrier diode according to claim 5, an opening is formed by selectively removing a part of the barrier metal layer or a region including the vicinity thereof on the conductor, and the opening is formed in the opening. Since a metal having a higher thermal expansion coefficient than the barrier metal layer is deposited and an electrode metal layer is formed on the metal and the barrier metal layer, the thermal expansion coefficient is higher than that of the barrier metal layer at a predetermined position in the barrier metal layer. Metal can be deposited with high accuracy. Therefore, the stress applied from the electrode metal layer to the barrier metal layer is efficiently dispersed to reduce the concentration near the upper surface of the sidewall of the trench, and an increase in reverse current (IR) due to the concentration of the stress is suppressed. A Schottky barrier diode can be easily manufactured.

According to the method for manufacturing a Schottky barrier diode according to claim 6, an opening is formed by selectively removing a part of the barrier metal layer or a part including the vicinity thereof on the conductor, and the opening and the barrier are formed. A metal having a higher thermal expansion coefficient than that of the barrier metal layer is deposited on the metal layer, and an electrode metal layer made of the metal is formed in the opening and on the barrier metal layer. Therefore, in the barrier metal layer and on the barrier metal layer. An electrode metal layer made of a metal having a higher thermal expansion coefficient than that of the barrier metal layer can be accurately formed at a predetermined position. Therefore, the stress applied from the electrode metal layer to the barrier metal layer is efficiently dispersed to reduce the concentration near the upper surface of the sidewall of the trench, and an increase in reverse current (IR) due to the concentration of the stress is suppressed. A Schottky barrier diode can be easily manufactured.
Further, the process of depositing the metal in the opening and the process of forming the electrode metal layer on the barrier metal layer can be performed in one process, so that the time required for the process can be reduced and the efficiency of the manufacturing equipment can be reduced. The manufacturing cost can be reduced.

1 is a cross-sectional view illustrating a trench structure type Schottky barrier diode (SBD) according to a first embodiment of the present invention. It is process drawing which shows the manufacturing method of trench structure type SBD of the 1st Embodiment of this invention. It is process drawing which shows the manufacturing method of trench structure type SBD of the 1st Embodiment of this invention. It is sectional drawing which shows the trench structure type Schottky barrier diode (SBD) of the 2nd Embodiment of this invention. It is sectional drawing which shows the trench structure type Schottky barrier diode (SBD) of the 3rd Embodiment of this invention. It is process drawing which shows the manufacturing method of trench structure type SBD of the 3rd Embodiment of this invention. It is sectional drawing which shows the Schottky barrier diode (SBD) of the trench structure type of the 4th Embodiment of this invention. It is sectional drawing which shows an example of the conventional trench structure type Schottky barrier diode (SBD).

A mode for carrying out the Schottky barrier diode and the manufacturing method thereof of the present invention will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[First Embodiment]
FIG. 1 is a cross-sectional view showing a trench structure type Schottky barrier diode (SBD) according to a first embodiment of the present invention. In FIG. 1, the same components as those in FIG. It is.
In FIG. 1, reference numeral 11 denotes a Schottky barrier diode (SBD), and a trench 3 having a rectangular cross section is formed on a surface (one main surface) 2 a of a silicon substrate (semiconductor substrate) 2. An insulating film 4 made of a silicon oxide film is formed, and a conductor 5 made of polycrystalline silicon is buried in the trench 3 in which the insulating film 4 is formed, and the surface 2a of the silicon substrate 2 and the outermost surface of the insulating film 4 are filled. The upper surface 4a and the upper surface 5a of the conductor 5 are flush with each other, and the barrier metal layer 12 and the electrode metal layer 7 are laminated so as to cover the silicon substrate 2, the insulating film 4, and the conductor 5.

This barrier metal layer 12 is made of Mo (linear expansion coefficient: 4.9 × 10 ⁻⁶ / K), Pt (linear expansion coefficient: 8.9 × 10 ⁻⁶ / K), Cr (linear expansion coefficient: 6.2). × 10 ⁻⁶ / K), Ti (linear expansion coefficient: 8.5 × 10 ⁻⁶ / K) or the like, or an alloy containing one or more of these metals. In addition, these linear expansion coefficients show an example at a predetermined temperature.
Here, the body expansion coefficient of the metal such as Mo is approximately three times the linear expansion coefficient.

An opening 13 is formed in a region of the barrier metal layer 12 on the conductor 5.
The opening area on the lower end 13a side of the opening 13 is narrower than the area of the upper surface of the conductor 5, and the cross-sectional shape of the opening 13 is a tapered shape that gradually increases from the upper end 13b toward the lower end 13a. A metal 14 having a higher thermal expansion coefficient (linear expansion coefficient and body expansion coefficient) than that of the barrier metal layer 12 is embedded in the opening 13.

The metal 14 only needs to have a higher coefficient of thermal expansion (linear expansion coefficient and body expansion coefficient) than the barrier metal layer 12, and is not particularly limited. For example, Al (linear expansion coefficient: 2.386 × 10 ⁻⁵ / K) , Cu (linear expansion coefficient: 1.62 × 10 ⁻⁵ / K), metal such as Pd (linear expansion coefficient: 1.176 × 10 ⁻⁵ / K), or one or more of these metals It is comprised by the alloy containing. Similar to the barrier metal layer 12, these linear expansion coefficients are also examples at a predetermined temperature.

  Thus, the barrier metal layer 12 is formed so as to cover the silicon substrate 2, the insulating film 4, and the conductor 5, and the barrier metal is formed in the opening 13 formed in the region of the barrier metal layer 12 on the conductor 5. Since the metal 14 having a higher thermal expansion coefficient (linear expansion coefficient and body expansion coefficient) than the layer 12 is embedded, when a stress such as a tensile stress generated in the electrode metal layer 7 is applied to the barrier metal layer 12, this metal 14 disperses the stress applied from the electrode metal layer 7 and alleviates the concentration of this stress near the upper surface of the side wall of the trench 3. As a result, an increase in reverse current (IR) due to stress concentration near the upper surface of the side wall of the trench 3 in the SBD 11 is suppressed.

Next, the manufacturing method of SBD11 is demonstrated based on FIG.2 and FIG.3.
First, as shown in FIG. 2A, the surface 2a of the silicon substrate 2 is thermally oxidized to form an insulating film 21 made of a silicon oxide film serving as a trench formation mask.
Next, a resist 22 is applied onto the insulating film 21, and exposure and development are performed to form an opening 22 a at a position corresponding to the trench of the resist 22.
Next, the insulating film 21 is etched using the resist 22 in which the opening 22 a is formed as a mask, and the opening 21 a is formed at a position corresponding to the trench of the insulating film 21.

Next, the resist 22 is removed, and carbon tetrafluoride (CF ₄ ) and oxygen (O ₂ ) are applied to the surface 2a of the silicon substrate 2 using the insulating film 21 in which the openings 21a are formed as a mask, as shown in FIG. ₂ ) and anisotropic etching using a mixed gas to form a trench 3 having a rectangular cross section on the surface 2 a of the silicon substrate 2. Thereafter, the insulating film 21 is removed.

Next, as shown in FIG. 2C, the entire surface 2 a of the silicon substrate 2 including the inside of the trench 3 is thermally oxidized to form an insulating film 23 made of a silicon oxide film in the surface 2 a of the silicon substrate 2 and the trench 3. To do.
Next, a conductive material 24 made of polycrystalline silicon is deposited on the insulating film 23 by thermal CVD. As a result, the conductive material 24 is deposited on the entire surface of the insulating film 23 including the inside of the trench 3.

Next, as shown in FIG. 2D, the conductive material 24 is etched by plasma CVD etching to remove the conductive material 24 deposited on the portion other than the inside of the trench 3, and the insulating film 23 in the mesa portion is exposed. Let
Next, the surface 2 a of the silicon substrate 2 and the surface of the conductive material 24 remaining in the trench 3 are etched by isotropic etching using hydrofluoric acid as an etching solution. Thereby, the insulating film 23 remaining in the trench 3 becomes the insulating film 4, the conductive material 24 in the trench 3 becomes the conductor 5, and the surface 2 a of the silicon substrate 2, the uppermost surface 4 a of the insulating film 4, and the conductor 5 The upper surface 5a is flush.

Next, as shown in FIG. 3A, a metal such as Mo, Pt, Cr, or Ti is deposited by vapor deposition so as to cover the surface 2a of the silicon substrate 2, the insulating film 4 and the conductor 5, thereby forming a metal layer. 25 is formed.
Next, a resist 26 is applied on the metal layer 25, and exposure and development are performed to form an opening 26 a at a position on the conductor 5 of the resist 26.

Next, the metal layer 25 is etched using the resist 26 in which the opening 26a is formed as a mask, and a tapered opening 25a expanded from the upper side to the lower side is formed at a position on the conductor 5 of the metal layer 25. Form.
Thereby, the metal layer 25 becomes the barrier metal layer 12 in which the opening 13 is formed in the region on the conductor 5.

  Next, as shown in FIG. 3B, a metal such as Al, Cu, or Pd having a higher thermal expansion coefficient (linear expansion coefficient and body expansion coefficient) than that of the barrier metal layer 12 is deposited by an evaporation method using the resist 26 as a mask. And deposit in the opening 13. As a result, the metal 27 is embedded in the opening 13, and the metal layer 28 is formed on the upper surface 26 a of the resist 26.

  Next, the resist 26 is removed by lift-off. As a result, the metal layer 27 formed on the upper surface 26a of the resist 26 is also removed at the same time, and as shown in FIG. 3 (c), only this opening 13 on the conductor 5 of the barrier metal layer 12 has this barrier. The metal 14 (27) having a higher thermal expansion coefficient (linear expansion coefficient and body expansion coefficient) than that of the metal layer 12 is embedded.

Next, as shown in FIG. 3D, an electrode metal layer 7 is formed by depositing an electrode metal such as Al, Cu, and Pd on the barrier metal layer 12 containing the metal 14 by vapor deposition.
As described above, the trench structure type SBD 11 of this embodiment can be manufactured.

  According to the trench structure type SBD 11 of this embodiment, the barrier metal layer 12 is formed so as to cover the silicon substrate 2, the insulating film 4, and the conductor 5, and an opening is formed in a region on the conductor 5 of the barrier metal layer 12. 13 is formed, and a metal 14 having a higher thermal expansion coefficient (linear expansion coefficient and body expansion coefficient) than that of the barrier metal layer 12 is embedded in the opening 13, so that tensile stress generated in the electrode metal layer 7, etc. Even when this stress acts on the barrier metal layer 12, this stress can be dispersed by the metal 14 embedded in the barrier metal layer 12, and the stress can be mitigated from being concentrated near the upper surface of the sidewall of the trench 3. . Therefore, an increase in reverse current (IR) due to stress concentration near the upper surface of the sidewall of trench 3 can be suppressed.

  According to the method for manufacturing the trench structure type SBD 11 of the present embodiment, the metal layer 25 is deposited so as to cover the surface 2a of the silicon substrate 2, the insulating film 4 and the conductor 5, and then the metal layer 25 is etched. The metal layer 25 is used as the barrier metal layer 12, and an opening 25a is formed at a position on the conductor 5 of the metal layer 25, and a metal 27 having a higher thermal expansion coefficient than the barrier metal layer 12 is deposited in the opening 25a. Therefore, stress such as tensile stress generated in the electrode metal layer 7 can be mitigated from being concentrated near the upper surface of the side wall of the trench 3, and therefore the reverse caused by the concentration of stress near the upper surface of the side wall of the trench 3. The SBD 11 that can suppress an increase in directional current (IR) can be easily manufactured.

[Second Embodiment]
FIG. 4 is a sectional view showing a trench structure type Schottky barrier diode (SBD) 31 according to the second embodiment of the present invention. The difference between the SBD 31 of this embodiment and the SBD 11 of the first embodiment is that In the SBD 11 of the first embodiment, the surface 2a of the silicon substrate 2, the uppermost surface 4a of the insulating film 4 and the upper surface 5a of the conductor 5 are flush with each other so as to cover the silicon substrate 2, the insulating film 4 and the conductor 5. The barrier metal layer 12 and the electrode metal layer 7 are laminated on each other, and the metal 14 having a higher thermal expansion coefficient than the barrier metal layer 12 is embedded in the opening 13 formed in the region on the conductor 5 of the barrier metal layer 12. On the other hand, in the SBD 31 of the present embodiment, the upper surface of the conductor 32 is a concave surface 32a, and the barrier metal layer 33 and the electrode metal so as to cover the silicon substrate 2, the insulating film 4, and the concave surface 32a of the conductor 32. 34 are stacked, in that embedded thermal expansion coefficient than that of the barrier metal layer 33 is a high metal 36 on the barrier metal layer 33 of the conductor opening 35 formed in the region on 32.

In this SBD 31, since the barrier metal layer 33 and the electrode metal layer 34 are laminated on the concave surface 32a of the conductor 32, the upper surface of the metal 36 embedded in the opening 35 of the barrier metal layer 33 is similar to the concave surface 32a. A concave surface 36 a having a shape is formed, and a concave surface 34 a having a shape similar to the concave surface 32 a is also formed on the upper surface of the electrode metal layer 34.
The compositions of the conductor 32, barrier metal layer 33, electrode metal layer 34, and metal 36 are exactly the same as those of the conductor 5, barrier metal layer 12, electrode metal layer 7, and metal 14 of the first embodiment. The description is omitted.

  The concave surface 32a of the conductor 32 controls the irradiation position and irradiation time of the plasma when the polycrystalline silicon 24 is etched by anisotropic etching using plasma in the manufacturing method of the SBD 11 of the first embodiment. Can be formed.

In this SBD 31, since the upper surface of the conductor 32 is a concave surface 32a, a concave surface 36a having a shape similar to the concave surface 32a is also formed on the upper surface of the metal 36 embedded in the opening 35 of the barrier metal layer 33 on the conductor 32, A concave surface 34 a having a shape similar to the concave surface 32 a is also formed on the upper surface of the electrode metal layer 34.
The concave surface 34a serves as a solder pool when solder or the like, which is an electrical joining material, is joined to the electrode metal layer 34, prevents the flow of solder at the time of solder joining, and improves the positional accuracy of the joined solder.

Also in the trench structure type SBD 31 of this embodiment, the same effect as the SBD 11 of the first embodiment can be obtained.
Moreover, since the upper surface of the conductor 32 is a concave surface 32a, and the barrier metal layer 33 and the electrode metal layer 34 are laminated so as to cover the silicon substrate 2, the insulating film 4, and the concave surface 32a of the conductor 32, the electrode metal layer 34 The concave surface 34a formed on the upper surface functions as a solder pool when solder or the like is joined to the electrode metal layer 34. As a result, it is possible to prevent the flow of solder or the like during solder joining, and the positional accuracy of the joined solder Can also be improved.

  In this SBD 31, only the upper surface of the conductor 32 is a concave surface 32a. However, in addition to the upper surface of the conductor 32, the uppermost surface 4a of the insulating film 4 may be a concave surface continuous with the concave surface 32a. Of course, the portion of the surface 2a corresponding to the upper surface of the side wall of the trench 3 may be a concave surface continuous with the concave surface 32a.

[Third Embodiment]
FIG. 5 is a cross-sectional view showing a trench structure type Schottky barrier diode (SBD) 41 according to the third embodiment of the present invention. The difference between the SBD 41 of this embodiment and the SBD 11 of the first embodiment is that In the SBD 11 of the first embodiment, a metal 14 having a thermal expansion coefficient higher than that of the barrier metal layer 12 is embedded in the opening 13 formed in the region on the conductor 5 of the barrier metal layer 12, and the barrier metal layer 12 and Whereas the electrode metal layer 7 is laminated so as to cover the metal 14, in the SBD 41 of the present embodiment, the metal embedded in the opening 13 and the electrode metal layer laminated on the barrier metal layer 12 are integrated. Therefore, an electrode metal layer 42 made of a metal having a higher thermal expansion coefficient than that of the barrier metal layer 12 is formed in the opening 13 formed in the region on the barrier metal layer 12 and the conductor 5 of the barrier metal layer 12. Is the point.

A concave surface 42 a is formed in a region on the conductor 5 on the upper surface of the electrode metal layer 42.
The electrode metal layer 42 is not particularly limited as long as it has a higher coefficient of thermal expansion (linear expansion coefficient and body expansion coefficient) than that of the barrier metal layer 12. For example, Al (linear expansion coefficient: 2.386 × 10 ⁻⁵ / K), Cu (linear expansion coefficient: 1.62 × 10 ⁻⁵ / K), Pd (linear expansion coefficient: 1.176 × 10 ⁻⁵ / K), or one or two of these metals It is comprised with the alloy containing a seed | species or more.

Next, the manufacturing method of SBD41 is demonstrated based on FIG.
Here, from the step of thermally oxidizing the surface 2a of the silicon substrate 2 to form the insulating film 21 serving as a trench formation mask, the step of forming the barrier metal layer 12 having the opening 13 formed in the region on the conductor 5 Up to this point, the method is the same as the method for manufacturing the SBD 11 of the first embodiment, and thus description thereof is omitted.

Here, as shown in FIG. 6A, after the barrier metal layer 12 having the opening 13 formed in the region on the conductor 5 is formed, the resist 26 formed on the barrier metal layer 12 is removed.
Next, as shown in FIG. 6B, a metal such as Al, Cu, or Pd having a higher coefficient of thermal expansion (linear expansion coefficient and body expansion coefficient) than that of the barrier metal layer 12 is removed from the opening 13 and the barrier by vapor deposition. Deposit on metal layer 12. As a result, an electrode metal layer 42 made of a metal having a higher thermal expansion coefficient than that of the barrier metal layer 12 is formed in the opening 13 formed on the barrier metal layer 12 and in the region of the barrier metal layer 12 on the conductor 5. As a result, a concave surface 42 a is formed in the region on the opening 13 in the upper surface of the electrode metal layer 42.
As described above, the trench structure type SBD 41 of this embodiment can be manufactured.

Also in the trench structure type SBD 41 of the present embodiment, the same operations and effects as the SBD 11 of the first embodiment can be achieved.
Moreover, an electrode metal layer 42 made of a metal having a higher thermal expansion coefficient than that of the barrier metal layer 12 is formed in the opening 13 formed in the region on the barrier metal layer 12 and the conductor 5 of the barrier metal layer 12. Therefore, the metal embedded in the opening 13 and the electrode metal layer laminated on the barrier metal layer 12 can be integrated, and the integrated electrode metal layer 42 is warped, cracked, peeled, etc. There is no risk of problems.

  Furthermore, since the concave surface 42a is formed in the region on the conductor 5 on the upper surface of the electrode metal layer 42, the concave surface 42a formed on the upper surface of the electrode metal layer 42 collects solder when bonding solder or the like to the electrode metal layer 42. As a result, it is possible to prevent the flow of solder at the time of solder bonding and to improve the positional accuracy of the bonded solder.

Also in the manufacturing method of the trench structure type SBD 41 of the present embodiment, the same operations and effects as the manufacturing method of the SBD 11 of the first embodiment can be achieved.
Moreover, the process of depositing the metal in the opening 13 and the process of forming the electrode metal layer on the barrier metal layer 12 can be performed in one process, so that the time required for the process can be shortened and the efficiency of the manufacturing equipment can be reduced. The manufacturing cost can be reduced.

[Fourth Embodiment]
FIG. 7 is a cross-sectional view showing a trench structure type Schottky barrier diode (SBD) 51 according to a fourth embodiment of the present invention. The difference between the SBD 51 of this embodiment and the SBD 11 of the first embodiment is that In the SBD 11 of the first embodiment, the surface 2a of the silicon substrate 2, the uppermost surface 4a of the insulating film 4 and the upper surface 5a of the conductor 5 are flush with each other so as to cover the silicon substrate 2, the insulating film 4 and the conductor 5. A barrier metal layer 12 and an electrode metal layer 7 are laminated on each other, an opening 13 is formed in a region of the barrier metal layer 12 on the conductor 5, and a metal 14 having a higher thermal expansion coefficient than the barrier metal layer 12 is formed in the opening 13. In contrast, in the SBD 51 of this embodiment, a concave portion 52 having a rectangular cross section is formed on the upper surface 5a of the conductor 5, and the thermal expansion coefficient is higher than that of the barrier metal layer 12 in the opening 13 including the concave portion 52 metal 3 is that embedded.

The metal 53 is different from the metal 14 of the first embodiment only in that it is embedded in the recess 52, and the composition of the metal 53 is exactly the same as that of the metal 14 of the first embodiment. Description is omitted.
The recess 52 of the conductor 5 controls the plasma irradiation position and irradiation time when the polycrystalline silicon 24 is etched by anisotropic etching using plasma in the method of manufacturing the SBD 11 of the first embodiment. Can be formed. Alternatively, a mask having an opening formed at a position corresponding to the recess 52 can be placed on the polycrystalline silicon 24, and the surface of the polycrystalline silicon 24 can be etched using this mask. .

Also in the trench structure type SBD 51 of the present embodiment, the same operations and effects as the SBD 11 of the first embodiment can be achieved.
In addition, a concave portion 52 having a rectangular cross section is formed on the upper surface 5a of the conductor 5, and a metal 53 having a higher thermal expansion coefficient than the barrier metal layer 12 is embedded in the opening 13 including the concave portion 52. Bonding strength with the body 5 can be increased, and problems such as warpage and peeling between the barrier metal layer 12 including the metal 53 and the conductor 5 can be prevented.

11 Schottky barrier diode (SBD)
2 Silicon substrate (semiconductor substrate)
2a Surface (one main surface)
3 Trench 4 Insulating film 4a Top surface 5 Conductor 5a Upper surface 7 Electrode metal layer 12 Barrier metal layer 13 Opening 13a Lower end 13b Upper end 14 Metal having high thermal expansion coefficient 21 Insulating film 21a Opening 22 Resist 22a Opening 23 Insulating film 24 Conductive material 25 Metal layer 25a Opening 26 Resist 26a Upper surface 26a Opening 27 Metal 31 SBD
32 Conductor 32a Concave surface 33 Barrier metal layer 34 Electrode metal layer 35 Opening 36 Metal 41 SBD
42 Electrode metal layer 42a Concave surface 51 SBD
52 Recess 53 Metal with high coefficient of thermal expansion

Claims (4)

A trench is formed on one main surface of the semiconductor substrate, an insulating film is formed on the inner surface of the trench, a conductor is embedded in the trench, a barrier metal layer is formed on the conductor, and the barrier metal layer In a Schottky barrier diode having an electrode metal layer formed thereon,
A metal having a higher coefficient of thermal expansion than the barrier metal layer is embedded in a part of the barrier metal layer or a region including the vicinity thereof on the conductor layer, and a lower end portion of the metal is disposed in the conductor. Embedded in a Schottky barrier diode.   2. The Schottky barrier diode according to claim 1, wherein the metal composition is the same as that of the electrode metal layer. 3. The Schottky barrier diode according to claim 1, wherein the upper surface of the conductor is a concave surface. Forming a trench in one main surface of the semiconductor substrate, forming an insulating film on the inner surface of the trench, embedding a conductor in the trench formed with the insulating film, forming a barrier metal layer on the conductor; In the method for manufacturing a Schottky barrier diode, in which an electrode metal layer is formed on the barrier metal layer,
A recess is formed on the upper surface of the conductor, an opening is formed by selectively removing a region of the barrier metal layer above the recess, and a thermal expansion coefficient is higher in the recess and the opening than the barrier metal layer. A method of manufacturing a Schottky barrier diode, comprising depositing a metal and forming the electrode metal layer on the metal and the barrier metal layer.

Images