JP2008227111A - Schottky barrier semiconductor device and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Schottky barrier semiconductor device capable of suppressing a drop of forward voltage of a large current area of a semiconductor device in which the surface of a Schottky contact has unevenness to save the contact area, and to provide a manufacturing method thereof. <P>SOLUTION: The semiconductor device has a structure in which a plurality of second N-type semiconductor layers 3 continuing from an N-type semiconductor substrate 1 are formed so as to extend in the layer of a low-concentration N-type semiconductor layer 4, a protrusion portion 8a forming a part of a Schottky metal 8 is formed between second N-type semiconductor layers 3 so as to extend into the layer of the low-concentration N-type semiconductor layer 4. In this structure, an electron flow is supplied from the second N-type semiconductor layer 3 to the Schottky metal 8, and thus, the entire surface of the Schottky contact surface becomes an effective current path to suppress the drop of a forward voltage of the large current area. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a Schottky barrier semiconductor device and a manufacturing method thereof, and particularly relates to a technique for suppressing a forward voltage drop.

  As a conventional Schottky barrier semiconductor device, there is one in which the area of the Schottky junction is increased by forming the Schottky junction surface in an uneven shape. FIG. 9 shows a conventional Schottky barrier semiconductor device.

In FIG. 9A, 101 is an n ⁺ silicon substrate, 102 is an n layer, 103 is a silicon oxide film, 104 is a metal film, 105 is a P region, 106 is a flat portion, 107 is a convex portion, and 111 is a Schottky. Each joint surface is shown.

In the semiconductor substrate, an n layer 102 is formed on an n ⁺ silicon substrate 101, and an annular P region 105 extending from the surface into the layer is formed in the n layer 102. A silicon oxide film 103 is formed on the peripheral portion of the n layer 102 forming one main surface of the semiconductor substrate, and the silicon oxide film 103 is annularly extended from the peripheral edge of the n layer 102 to the middle of the P region 105. Covered.

  A metal film 104 is formed in a region surrounded by the silicon oxide film 103 on the main surface on one side of the semiconductor substrate. The metal film 104 covers a part of the n layer 102 and the P region 105 and has a peripheral portion thereof. It extends onto the silicon oxide film 103.

  At the interface between the n layer 102 and the metal film 104, a flat portion 106 and a convex portion 107 are formed on the metal film 104, and the Schottky junction surface 111 is formed into an uneven shape by the flat portion 106 and the convex portion 107. The key joint surface 111 is enlarged to increase its area.

According to this configuration, since the area of the Schottky junction surface 111 is increased, a voltage drop due to the forward current can be suppressed.
JP-A-9-283377

However, in the conventional configuration described above, the electron current of the forward current that reaches the metal layer 104 from the n ⁺ silicon substrate 101 through the n layer 102 tends to concentrate on the convex portion 107 and hardly reach the flat portion 106. Have This is because the electric resistance component of the metal layer 104 is lower than that of the n layer 102 and the shortest path is formed in the convex portion 107.

  This tendency becomes more prominent as the forward current increases and as the protrusion distance of the protrusion 107 increases. For this reason, as shown in FIG. 9B, a semiconductor device having a concavo-convex shape on the Schottky junction surface in comparison with a semiconductor device having a planar structure on the Schottky junction surface has a voltage drop in a region where the forward current is small. However, as the forward current increases, the effect of suppressing the voltage drop due to the current decreases and there is no difference between the two, so there is a problem that a uniform effect cannot be obtained in a wide current range. Was.

  The present invention solves the above problems, and a Schottky barrier semiconductor device capable of uniformly suppressing a voltage drop in a wide current region from a small current region to a large current region of a forward current and a method for manufacturing the same. The purpose is to provide.

  In order to solve the above problems, a Schottky barrier semiconductor device according to the present invention is a low-concentration semiconductor layer in which a semiconductor substrate has a plurality of semiconductor layers formed on a base layer, and has the same conductivity type on the base layer. A guard ring layer having a conductivity type different from that of the low-concentration semiconductor layer is formed in an annular shape extending from the surface of the low-concentration semiconductor layer into the layer and having the same conductivity type as the low-concentration semiconductor layer A first semiconductor layer is formed in an annular shape so as to extend from the interface between the base layer and the low-concentration semiconductor layer into the low-concentration semiconductor layer and to face the guard ring layer. A plurality of second semiconductor layers having the same conductivity type as the low concentration semiconductor layer extend from the interface between the base layer and the low concentration semiconductor layer into the layer of the low concentration semiconductor layer in a region surrounded by Formed in parallel with each other, the semiconductor An annular insulating protective film is formed on the peripheral edge of the main surface on one side of the substrate so as to cover from the peripheral edge of the low-concentration semiconductor layer to the middle of the guard ring layer, and is surrounded by the insulating protective film. A Schottky metal is formed on one main surface, and the Schottky metal covers a part of the low-concentration semiconductor layer and the guard ring layer, and a peripheral portion of the Schottky metal extends above the insulating protective film. A plurality of Schottky metal protrusions extending into the low-concentration semiconductor layer and formed in parallel with each other, and the protrusions are located between the second semiconductor layers, A metal electrode is formed on the Schottky metal.

  Further, a third semiconductor layer having a conductivity type different from that of the low-concentration semiconductor layer is formed at a tip position facing the other main surface side of the semiconductor substrate in each projecting portion of the Schottky metal. And

In addition, an insulating layer is formed at a tip position facing each other main surface side of the semiconductor substrate in each projecting portion of the Schottky metal.
Further, a second Schottky metal is formed at a tip position facing each other main surface side of the semiconductor substrate in each projecting portion of the Schottky metal.

  A method for manufacturing a Schottky barrier semiconductor device according to the present invention is a method for manufacturing a semiconductor device using a semiconductor substrate in which a plurality of semiconductor layers are formed on a base layer. The low concentration of the same conductivity type by epitaxial growth on the base layer An initial oxidation step of forming a semiconductor layer and forming an insulating protective film on the low-concentration semiconductor layer by a thermal oxidation method; and selectively etching the insulating protective film to open a predetermined portion and opening the predetermined portion The low concentration semiconductor layer is exposed by exposing the surface of the low concentration semiconductor layer, implanting a dopant having the same conductivity type as the low concentration semiconductor layer using the insulating protective film as a mask, and performing drive diffusion by a thermal diffusion method. An annular first semiconductor layer extending from the surface of the substrate to reach the base layer and a plurality of mutually parallel second semiconductor layers are formed, and the second semiconductor layer is formed as the first semiconductor layer. A first conductive type semiconductor layer forming step formed in a region surrounded by the semiconductor layer; and all of the insulating protective film is removed by etching, the first semiconductor layer, the second semiconductor layer, and the low concentration semiconductor A low-concentration semiconductor layer stacking step of forming a low-concentration semiconductor layer on the surface of the layer by epitaxial growth and forming the insulating protective film again on the stacked low-concentration semiconductor layer; The insulating protective film is selectively etched to form grooves in predetermined portions, the side and bottom portions of the grooves are subjected to sacrificial oxidation, and the insulating protective film is selectively etched again to open windows in the predetermined portions. Forming a window to expose the surface of the low-concentration semiconductor layer, and forming a different conductivity type from the low-concentration semiconductor layer using the insulating protective film as a mask on the exposed surface of the low-concentration semiconductor layer -By injecting a punt and performing drive diffusion by a thermal diffusion method, a guard ring layer that extends from the surface of the low-concentration semiconductor layer into the layer and faces the first semiconductor layer is formed. A guard ring layer forming step, and an annular insulating protective film that covers the insulating ring from the peripheral edge of the main surface on one side of the semiconductor substrate to the middle of the guard ring layer by selectively etching the insulating protective film. An insulating protective film removing step for removing the insulating protective film in other portions to expose a surface of the low-concentration semiconductor layer including the groove and a part of the surface of the guard ring layer; and A Schottky metal is formed on one main surface of the semiconductor substrate surrounded by sputtering by sputtering, the Schottky metal covers the exposed surfaces of the low-concentration semiconductor layer and the guard ring layer, and the shot A peripheral portion of the key metal extends on the insulating protective film, and a projecting portion that forms a part of the Schottky metal is formed in the groove of the low-concentration semiconductor layer. And a metal forming step of forming a metal electrode by sputtering on the Schottky metal.

  A method for manufacturing a Schottky barrier semiconductor device according to the present invention is a method for manufacturing a semiconductor device using a semiconductor substrate in which a plurality of semiconductor layers are formed on a base layer, wherein the substrate of the semiconductor substrate is selectively etched away. Forming an annular first semiconductor layer reaching the base layer from the surface of the base material, and parallel to each other in a region surrounded by the first semiconductor layer from the surface of the base material to the base layer A semiconductor layer forming step of forming a plurality of second semiconductor layers reaching, and epitaxial growth of a low concentration semiconductor layer having the same conductivity type as the base layer on the base layer, the first semiconductor layer, and the second semiconductor layer Forming a plurality of grooves toward the base layer between the second semiconductor layers by selectively etching the low-concentration semiconductor layer, And wherein the Mukoto.

A method for manufacturing a Schottky barrier semiconductor device according to the present invention is a method for manufacturing a semiconductor device using a semiconductor substrate in which a plurality of semiconductor layers are formed on a base layer, and a predetermined portion of a main surface on one side of the base layer of the semiconductor substrate. A doping step of implanting a dopant having the same conductivity type as the base layer to form a first semiconductor layer doping portion and a second semiconductor layer doping portion;
A low-concentration semiconductor layer having the same conductivity type as that of the base layer is formed by epitaxial growth on one main surface of the base layer, and the first semiconductor layer doping portion and the second semiconductor layer doping portion are formed. By diffusing the dopant into the low concentration semiconductor layer to a desired position, an annular first semiconductor layer is formed in the low concentration semiconductor layer, and in a region surrounded by the first semiconductor layer. A low-concentration semiconductor layer that forms a plurality of second semiconductor layers parallel to each other and selectively etches the low-concentration semiconductor layer to form a plurality of grooves toward the base layer between the second semiconductor layers It includes a stacking process.

  As described above, according to the present invention, the Schottky metal extends into the layer of the low-concentration semiconductor layer at the plurality of protrusions to enlarge the Schottky junction surface, and the plurality of the Schottky metal bonded to the base layer of the semiconductor substrate. The second semiconductor layer extends into the low-concentration semiconductor layer, and the second semiconductor layer is close to the Schottky metal in the direction between the main surfaces of the semiconductor substrate. The main surface on one side of the semiconductor substrate by the second semiconductor layer supplying the electron current to the Schottky metal and the second N-type semiconductor layer being positioned in parallel between the protrusions of the Schottky metal All the Schottky junction surfaces at the interface between the low-concentration semiconductor layer and the Schottky metal in the semiconductor layer and the interface between the low-concentration semiconductor layer and the protrusion in the low-concentration semiconductor layer are effective current-passing cross sections. Also it is possible to suppress the voltage drop uniformly and it is possible to suppress the voltage drop in a wide current region from the small-current region of the forward current to a large current region.

Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment 1)
1A and 1B show a Schottky barrier semiconductor device according to a first embodiment of the present invention. FIG. 1A is a cross-sectional view of the Schottky barrier semiconductor device, and FIG. 1B shows a semiconductor in the Schottky barrier semiconductor device. It is the state which removed the electrode comprised on a board | substrate and Schottky metal, and is AA arrow sectional drawing of (a).

  In FIG. 1, 1 is an N-type semiconductor substrate, 2 is a first N-type semiconductor layer, 3 is a second N-type semiconductor layer, 4 is a low-concentration N-type semiconductor layer, 5 is a P-type guard ring layer, and 6 is A semiconductor substrate, 7 is an insulating protective film, 8 is a Schottky metal, 8a is a projecting portion of the Schottky metal, and 9 is a metal electrode.

  In FIG. 1, a semiconductor substrate 6 has a low concentration N-type semiconductor layer 4 formed on an N-type semiconductor substrate 1 made of silicon as a base layer. A P-type guard ring layer 5 is formed in an annular shape in the low-concentration N-type semiconductor layer 4, and the P-type guard ring layer 5 is a low-concentration N-type semiconductor layer 4 that forms the main surface on one side of the semiconductor substrate 6. Extends from the surface into the layer. Further, the first N-type semiconductor layer 2 is formed in an annular shape facing the P-type guard ring layer 5 in the low-concentration N-type semiconductor layer 4, and the first N-type semiconductor layer 2 is an N-type semiconductor substrate. 1 extends from the interface between the low concentration N-type semiconductor layer 4 and the low concentration N-type semiconductor layer 4.

  In the low-concentration N-type semiconductor layer 4 of the semiconductor substrate 6, a plurality of second N-type semiconductor layers 3 are formed in a plate shape parallel to each other in an inner region surrounded by the first N-type semiconductor layer 2. The second N-type semiconductor layer 3 extends from the interface between the N-type semiconductor substrate 1 and the low-concentration N-type semiconductor layer 4 into the layer of the low-concentration N-type semiconductor layer 4. The shape of the second N-type semiconductor layer 3 is not limited to a plate shape, and a plurality of columnar second N-type semiconductor layers 3 can be arranged in a row, and arranged in a scattered state. Also good.

  The semiconductor substrate 6 includes a low concentration N-type semiconductor layer 4 and a P-type guard ring layer 5 on one side, and an N-type semiconductor substrate 1 on the other side that is opposite to the main surface on one side. An insulating protective film 7 made of silicon oxide is formed in an annular shape at the peripheral edge of the low-concentration N-type semiconductor layer 4 forming one main surface of the semiconductor substrate 6, and the insulating protective film 7 is formed of a low-concentration N-type semiconductor layer. 4 is circularly covered from the peripheral edge of 4 to the middle position on the P-type guard ring layer 5.

  A Schottky metal 8 is formed in a region surrounded by the insulating protective film 7 on the main surface on one side of the semiconductor substrate 6. The Schottky metal 8 is composed of the low-concentration N-type semiconductor layer 4 and the P-type guard ring layer 5. The peripheral surface of the insulating protective film 7 extends over the exposed surface.

  The Schottky metal 8 has a plurality of projecting portions 8a. The projecting portions 8a extend from the Schottky metal 8 into the layer of the low-concentration N-type semiconductor layer 4 to form a plate shape parallel to each other. Each of the portions 8 a is located in the middle between the second N-type semiconductor layers 3. A metal electrode 9 is formed on the Schottky metal 8. The shape of the protruding portion 8a is not limited to a plate shape, and a plurality of columnar second N-type semiconductor layers 3 can be arranged in a row, or may be arranged in a scattered state.

  According to the above-described configuration, the Schottky metal 8 formed on the main surface on one side of the semiconductor substrate 6 is a low-concentration N-type semiconductor layer toward the main surface on the other side of the semiconductor substrate 6 at the plurality of protrusions 8a. 4, the Schottky junction surface forming the interface between the Schottky metal 8 and the low-concentration N-type semiconductor layer 4 is enlarged, and the area thereof is increased.

  Further, a plurality of second N-type semiconductor layers 3 bonded to the N-type semiconductor substrate 1 forming the other main surface of the semiconductor substrate 6 are lightly doped N-type semiconductor layers toward the one main surface of the semiconductor substrate 6. 4, the second N-type semiconductor layer 3 comes close to the Schottky metal 8 in the direction between the main surfaces of the semiconductor substrate 6. The second N-type semiconductor layer 3 supplies an electron flow to the Schottky metal 8.

  The second N-type semiconductor layer 3 is positioned in parallel between the protrusions 8 a of the Schottky metal 8, and the protrusion 8 a and the second N-type semiconductor layer 3 are along the main surface of the semiconductor substrate 6. By facing each other in the direction, the low-concentration N-type at the entire interface forming the Schottky junction surface between the Schottky metal 8 including the protrusion 8 a and the low-concentration N-type semiconductor layer 4, that is, the main surface on one side of the semiconductor substrate 6. All the Schottky junction surfaces at the interface between the semiconductor layer 4 and the Schottky metal 8 and the interface between the low concentration N-type semiconductor layer 4 and the protruding portion 8a in the layer of the low concentration N-type semiconductor layer 4 are effective in passing current. The cross section makes it possible to suppress the voltage drop even in a large current region.

  Therefore, as shown in FIG. 1C, the Schottky barrier semiconductor device according to the present invention is compared with a semiconductor device having a planar structure of a Schottky junction surface from a small current region to a large current region of the forward current. It is possible to suppress the voltage drop uniformly in a wide current range.

  Here, it is preferable that the size of the protruding portion 8a of the Schottky metal 8 and the interval between them are uniformly equal. Moreover, it is preferable that the size of the 2nd N type semiconductor layer 3 is equal equally, and it is preferable that the space | interval between them is equal to the space | interval between the protrusion parts 8a, and the 2nd N type semiconductor layer 3 is It is preferable that the distance between the protrusions 8a of the Schottky metal 8 is maintained at the center between them.

  According to these preferable conditions, the bias between the electric field and current during operation can be prevented, so that the operation as a Schottky barrier semiconductor device can be made more stable and reliable.

In the present embodiment, the plurality of second N-type semiconductor layers 3 and the Schottky metal protrusions 8a are described as being formed in parallel. However, as described above, a columnar shape or the like interspersed with both. However, similar effects can be obtained.
(Embodiment 2)
FIG. 2 is a cross-sectional view of the Schottky barrier semiconductor device according to the second embodiment of the present invention. In FIG. 2, the same components as those in FIG.

  In FIG. 2, the Schottky metal 8 formed on one main surface of the low-concentration N-type semiconductor layer 4 has a plurality of protrusions 8a extending into the layer of the low-concentration N-type semiconductor layer 4. In addition, a P-type semiconductor layer 10 is formed at a tip position of the protruding portion 8a, that is, a portion facing the other main surface side.

According to said structure, the strong electric field in the front-end | tip of the protrusion part 8a at the time of application of a reverse bias can be relieve | moderated. That is, in the configuration shown in FIG. 1, an electric field concentration is induced at the tip of the protrusion 8a when a reverse bias is applied, and a strong electric field is generated at the tip of the protrusion 8a. However, in the second embodiment, the amount of negative charge accumulated per unit volume when a reverse bias is applied is much smaller in the P-type semiconductor layer 10 than in the Schottky metal 8. The electric field concentration induced at the tip of the protrusion 8a is relaxed and the electric field is weakened. For this reason, in addition to the forward voltage drop suppression effect obtained in the first embodiment, the leakage current suppression effect is obtained.
(Embodiment 3)
FIG. 3 is a cross-sectional view of the Schottky barrier semiconductor device according to the third embodiment of the present invention. In FIG. 3, the same components as those in FIG.

  In FIG. 3, the Schottky metal 8 formed on one main surface of the low-concentration N-type semiconductor layer 4 has a plurality of protrusions 8 a extending into the layer of the low-concentration N-type semiconductor layer 4. In addition, an insulating layer 11 made of silicon oxide or the like is formed at the tip position of the protruding portion 8a, that is, at the portion facing the other main surface side.

According to the above configuration, the insulating layer 11 blocks the leakage current at the tip of the protruding portion 8a when the reverse bias is applied. That is, when a reverse bias is applied, an electric field concentration is induced at the tip of the protrusion 8a and a strong electric field is generated at the tip of the protrusion 8a, but the insulating layer 11 blocks the leakage current. Therefore, in addition to the forward voltage drop suppression effect obtained in the first embodiment, the leakage current suppression effect is obtained.
(Embodiment 4)
FIG. 4 is a cross-sectional view of the Schottky barrier semiconductor device according to the fourth embodiment of the present invention. In FIG. 4, the same components as those in FIG.

  In FIG. 4, the Schottky metal 8 formed on one main surface of the low-concentration N-type semiconductor layer 4 has a plurality of protrusions 8a extending into the layer of the low-concentration N-type semiconductor layer 4. In addition, a second Schottky metal 12 is formed at the tip position of the protruding portion 8a, that is, at the portion facing the other main surface.

  According to the above configuration, the electrical characteristics of the Schottky barrier semiconductor device are continuously changed only by changing the ratio of the Schottky metal 8 and the second Schottky metal 12 occupying the entire area of the Schottky junction surface. be able to.

  Therefore, as shown in the first embodiment, it is possible to realize a Schottky barrier semiconductor device that uses all the Schottky junction surfaces as effective current passing sections and has optimum electrical characteristics according to the intended use. it can.

  For example, when a metal that lowers the barrier height is used as the Schottky metal 8 and a metal that increases the barrier height is used as the second Schottky metal 12, the interface between the Schottky metal 8 and the second Schottky metal 12 is used. If the position is moved to one main surface side, a Schottky barrier semiconductor device having relatively low leakage characteristics can be realized. Alternatively, if the interface position between the Schottky metal 8 and the second Schottky metal 12 is moved to the other main surface, a Schottky barrier semiconductor device with a relatively small forward voltage drop can be realized. .

  A method for manufacturing a Schottky barrier semiconductor device according to the present invention will be described below. 5 and 6 show a cross section of the Schottky barrier semiconductor device at the end of the main steps of the manufacturing process.

  5 and 6, 1 is an N-type semiconductor substrate, 2 is a first N-type semiconductor layer, 3 is a second N-type semiconductor layer, 4 is a low-concentration N-type semiconductor layer, 4a is a groove, and 5 is P A type guard ring layer, 6 is a semiconductor substrate, 7 is an insulating protective film, 7a is a window, 8 is a Schottky metal, 8a is a Schottky metal protrusion, and 9 is a metal electrode.

  FIG. 5A shows an initial oxidation step. A low-concentration N-type semiconductor layer 4 is formed by epitaxial growth on an N-type semiconductor substrate 1 made of silicon which forms the base layer of the semiconductor substrate. An insulating protective film 7 is obtained by forming silicon oxide on the semiconductor layer 4 by thermal oxidation.

  FIG. 5B shows an N-type semiconductor layer forming step, in which selective etching removal is performed after the initial oxidation step, and a predetermined portion of the insulating protective film 7, that is, the first N-type semiconductor layer 2 and A portion located at a portion where the second N-type semiconductor layer 3 is to be formed is opened in a predetermined shape to expose the surface of the low-concentration N-type semiconductor layer 4.

  Next, phosphorus, which is an N-type dopant, is implanted into the surface of the low-concentration N-type semiconductor layer 4 using the insulating protective film 7 as a mask, and drive diffusion is performed by a thermal diffusion method to thereby form a first annular N-type semiconductor layer 2. And a plurality of parallel second N-type semiconductor layers 3 are formed. The first N-type semiconductor layer 2 extends from the surface of the low-concentration N-type semiconductor layer 4 into the layer and reaches the N-type semiconductor substrate 1, and the second N-type semiconductor layer 3 is formed of a ring-shaped first N-type semiconductor layer 2. Extends from the surface of the low-concentration N-type semiconductor layer 4 surrounded by the n-type semiconductor layer 2 into the layer and reaches the n-type semiconductor substrate 1. Note that an insulating protective film 7 is formed again on the first N-type semiconductor layer 2 and the second N-type semiconductor layer 3 by heat during drive diffusion. FIG. 5B shows this state.

  FIG. 5C shows a low-concentration N-type semiconductor layer stacking step. After the previous N-type semiconductor layer forming step, all of the insulating protective film 7 is removed by etching, and the first N-type semiconductor layer 2 is removed. The low-concentration N-type semiconductor layer 4 is again stacked on the surfaces of the second N-type semiconductor layer 3 and the low-concentration N-type semiconductor layer 4 by epitaxial growth. Next, the insulating protective film 7 is formed again on the stacked low concentration N-type semiconductor layer 4.

  FIG. 5 (d) shows a groove forming process. After the low-concentration N-type semiconductor layer stacking step, selective etching removal is performed, and the low-concentration N-type semiconductor layer 4 and the insulation protection located thereon are provided. A plurality of parallel grooves 4 a having a predetermined shape are carved in a predetermined portion of the film 7, that is, a portion located in a portion where the projecting portion 8 a of the Schottky metal 8 is to be formed. Here, the groove 4a is located at the center between the second N-type semiconductor layers 3 and has a predetermined depth.

  FIG. 6A shows a window opening process. After the previous groove forming process, sacrificial oxidation is performed on the side and bottom of the groove 4a, and the insulation located on the first N-type semiconductor layer 2 is shown. The protective film 7 is selectively etched away, and an annular window 7a is formed in a predetermined portion of the insulating protective film 7, that is, a portion where the P-type guard ring layer 5 is to be formed, to form the low-concentration N-type semiconductor layer 4 To expose the surface.

  FIG. 6B shows a P-type guard ring layer forming process. After the previous window opening process, P is formed on the surface of the low-concentration N-type semiconductor layer 4 exposed to the window 7a using the insulating protective film 7 as a mask. Boron, which is a type dopant, is implanted, and drive diffusion is performed by a thermal diffusion method to form a P type guard ring layer 5. The P-type guard ring layer 5 extends from the surface of the low-concentration N-type semiconductor layer 4 into the layer and has a ring shape facing the first N-type semiconductor layer 2. At this point, the semiconductor substrate 6 including the N-type semiconductor substrate 1, the first N-type semiconductor layer 2, the second N-type semiconductor layer 3, the low-concentration N-type semiconductor layer 4, and the P-type guard ring layer 5 is configured. Is done.

  FIG. 6C shows an insulating protective film removing process. After the previous P-type guard ring forming process, the insulating protective film 7 is selectively etched, and the peripheral edge of the main surface on one side of the semiconductor substrate 6 is shown. The remaining part of the insulating protective film 7 is removed while leaving the annular insulating protective film 7 covering the part. As a result, the remaining annular insulating protective film 7 covers from the peripheral portion of the low-concentration N-type semiconductor layer 4 to the middle position of the P-type guard ring layer 5, and the surface of the low-concentration N-type semiconductor layer 4 including the groove 4 a A part of the surface of the P-type guard ring layer 5 is exposed.

  FIG. 6D shows a metal forming process. After the previous insulating protective film removing process, the main surface on one side of the semiconductor substrate 6 surrounded by the insulating protective film 7, that is, the groove 4a is formed by sputtering. A Schottky metal 8 made of titanium and a protruding portion 8a that is a part of the Schottky metal 8 are formed on the surface of the low-concentration N-type semiconductor layer 4 containing P and the surface of a part of the P-type guard ring layer 5. The Schottky metal 8 covers the surface of the low-concentration N-type semiconductor layer 4 and a part of the surface of the P-type guard ring layer 5, and its peripheral portion extends to the peripheral portion of the insulating protective film 7 to form the groove 4 a. The protruding portion 8a extends into the layer of the low-concentration N-type semiconductor layer 4 toward the other main surface of the semiconductor substrate 6, and is located in the center between the second N-type semiconductor layers 3, It has a predetermined depth.

  Next, a metal electrode 9 made of silver as an anode is formed on the Schottky metal 8 by sputtering. As a result, the plurality of second N-type semiconductor layers 3 extend from the other main surface side of the semiconductor substrate 6 toward the one main surface side into the layer of the low-concentration N-type semiconductor layer 4. Of the second N-type semiconductor layer 3 extends from the main surface on one side of the semiconductor substrate 6 toward the other main surface into the low-concentration N-type semiconductor layer 4. Thus, the Schottky barrier semiconductor device is formed in a state in which the protruding portion 8a is located at the center between and the second N-type semiconductor layer 3 is located at the center between the protruding portions 8a.

  Here, the first N-type semiconductor layer 2, the second N-type semiconductor layer 3, the low-concentration N-type semiconductor layer 4, and the groove are formed in the N-type semiconductor substrate 1 shown in FIGS. The method of forming 4a may be the method shown in FIG.

FIG. 7A shows an N-type semiconductor substrate 1.
FIG. 7B shows an N-type semiconductor layer forming step. The N-type semiconductor remaining at the bottom by selectively etching away the N-type semiconductor substrate 1 having a predetermined thickness as a base material of the semiconductor substrate. The substrate 1 forms the base layer portion of the semiconductor substrate, and the annular first N-type semiconductor layer 2 reaching the base layer from the surface of the N-type semiconductor substrate 1 as the original base material is formed. A plurality of second N-type semiconductor layers 3 reaching the base layer from the surface of the N-type semiconductor substrate 1 as an original base material are formed in a region surrounded by the type semiconductor layer 2 in parallel with each other.

  FIG. 7C shows a low-concentration N-type semiconductor layer stacking step. After the previous N-type semiconductor layer forming step, the N-type semiconductor substrate 1, the first N-type semiconductor layer 2, and the second N-type semiconductor layer are formed. A low-concentration N-type semiconductor layer 4 is formed on the type semiconductor layer 3 by epitaxial growth. Then, the low-concentration N-type semiconductor layer 4 is selectively etched to carve a plurality of grooves 4 a toward the N-type semiconductor substrate 1 between the second N-type semiconductor layers 3.

Here, the dopant concentrations of the N-type semiconductor substrate 1, the first N-type semiconductor layer 2, and the second N-type semiconductor layer 3 do not have to be different, and may be the same.
Further, the first N-type semiconductor layer 2, the second N-type semiconductor layer 3, the low-concentration N-type semiconductor layer 4, and the groove 4a are formed on the N-type semiconductor substrate 1 shown in FIGS. 5 (a) to 5 (d). Another method of forming is shown in FIG.

  FIG. 8A shows a doping process, in which an N-type dopant is implanted into a portion where the first N-type semiconductor layer 2 is to be formed on one main surface of the N-type semiconductor substrate 1 that forms the base layer of the semiconductor substrate. Then, the first N-type semiconductor layer topping portion 2a is formed, and the N-type dopant is injected into the portion where the second N-type semiconductor layer 3 is to be formed, so that the second N-type semiconductor layer doping portion 3a is formed. Form.

  FIG. 8B shows a low-concentration N-type semiconductor layer stacking step, in which a low-concentration N-type semiconductor layer 4 is formed on one main surface of the N-type semiconductor substrate 1 by epitaxial growth. At this time, using the heat applied in the same step, the dopants of the first N-type semiconductor layer doping part 2 a and the second N-type semiconductor layer doping part 3 a are introduced into the low-concentration N-type semiconductor layer 4. By diffusing to a desired position, the first N-type semiconductor layer 2 and the second N-type semiconductor layer 3 are formed. Then, the low-concentration N-type semiconductor layer 4 is selectively etched to carve a groove 4 a toward the N-type semiconductor substrate 1 between the second N-type semiconductor layers 3. As a result, as in FIG. 5D, the N-type semiconductor substrate 1, the first N-type semiconductor layer 2, the second N-type semiconductor layer 3, the low-concentration N-type semiconductor layer 4, and the trench 4a are formed. The

According to these manufacturing methods, drive diffusion is not required when the first N-type semiconductor layer 2 and the second N-type semiconductor layer 3 are formed.
In each of the embodiments of the present invention described above, the number of protrusions 8a of the Schottky metal 8 is smaller than that of the second N-type semiconductor layer 3, and all the protrusions 8a are the second N-type semiconductor layer 3. The configuration is described as being located between the two.

  However, the present invention is not limited to the above-described embodiment, and the same number of second N-type semiconductor layers 3 and projecting portions 8a of Schottky metal 8 are provided, and the outermost side on one side in the arrangement direction. It is also possible to adopt a configuration in which the protruding portion 8a of the Schottky metal 8 is positioned outside the second N-type semiconductor layer 3.

  Further, the number of projecting portions 8a of the Schottky metal 8 is larger than that of the second N-type semiconductor layer 3, and the Schottky metal is positioned outside the outermost second N-type semiconductor layer 3 on both sides in the arrangement direction. It is also possible to adopt a configuration in which eight protruding portions 8a are located.

  In the embodiment of the present invention, the semiconductor substrate, the first semiconductor layer, and the second semiconductor layer are described as N-type, and the guard ring layer is described as P-type. However, the present invention is not limited to this. You may reverse both. In that case, the anode becomes the cathode.

  The present invention is useful as a Schottky barrier semiconductor device, and is particularly suitable for a device that conducts a large current.

BRIEF DESCRIPTION OF THE DRAWINGS The Schottky barrier semiconductor device in Embodiment 1 of this invention is shown, (a) is sectional drawing, (b) is AA arrow sectional drawing of (a), (c) is the performance with the past. Graph showing a comparison of Sectional drawing of the Schottky barrier semiconductor device in Embodiment 2 of this invention Sectional drawing of the Schottky barrier semiconductor device in Embodiment 3 of this invention Sectional drawing of the Schottky barrier semiconductor device in Embodiment 4 of this invention Sectional drawing which shows the main processes in the manufacturing method of this invention Sectional drawing which shows the main processes in the manufacturing method Sectional drawing which shows the main processes in the other manufacturing method of this invention Sectional drawing which shows the main processes in the other manufacturing method of this invention 1 shows a conventional Schottky barrier semiconductor device, where (a) is a cross-sectional view and (b) is a graph showing a comparison of conventional performance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 N type semiconductor substrate 2 1st N type semiconductor layer 2a 1st doping part for N type semiconductor layers 3 2nd N type semiconductor layer 3a 2nd doping part for N type semiconductor layers 4 Low concentration N type semiconductor layer 4a Groove 5 P-type guard ring layer 6 Semiconductor substrate 7 Insulating protective film 7a Window 8 Schottky metal 8a Schottky metal protrusion 9 Metal electrode 10 P-type semiconductor layer 11 Insulating layer 12 Second Schottky metal 101 n ⁺ Silicon substrate 102 n layer 103 silicon oxide 104 metal film 105 P region 106 flat part 107 convex part 111 Schottky junction surface

Claims (7)

A semiconductor substrate having a plurality of semiconductor layers formed on a base layer, wherein a low concentration semiconductor layer having the same conductivity type is formed on the base layer, and a guard ring layer having a conductivity type different from that of the low concentration semiconductor layer is provided. A first semiconductor layer extending from the surface of the low-concentration semiconductor layer into the layer and formed in a ring shape and having the same conductivity type as the low-concentration semiconductor layer is formed from the interface between the base layer and the low-concentration semiconductor layer. A plurality of layers extending into the low-concentration semiconductor layer so as to face the guard ring layer and having the same conductivity type as that of the low-concentration semiconductor layer in a region surrounded by the first semiconductor layer A second semiconductor layer extending from the interface between the base layer and the low-concentration semiconductor layer into the low-concentration semiconductor layer and formed in parallel with each other,
An annular insulating protective film is formed on the peripheral edge of the main surface on one side of the semiconductor substrate so as to cover from the peripheral edge of the low-concentration semiconductor layer to the middle of the guard ring layer, and is surrounded by the insulating protective film A Schottky metal is formed on the main surface on one side of the substrate, the Schottky metal covers a part of the low-concentration semiconductor layer and the guard ring layer, and the peripheral edge of the Schottky metal extends to the insulating protective film. A plurality of Schottky metal protrusions extending into the low-concentration semiconductor layer and formed in parallel with each other, and the protrusions are positioned between the second semiconductor layers, respectively. A Schottky barrier semiconductor device, wherein a metal electrode is formed on the Schottky metal. A third semiconductor layer having a conductivity type different from that of the low-concentration semiconductor layer is formed at a tip position facing the other main surface side of the semiconductor substrate in each projecting portion of the Schottky metal. The Schottky barrier semiconductor device according to claim 1. 2. The Schottky barrier semiconductor device according to claim 1, wherein an insulating layer is formed at a tip position facing each other main surface side of the semiconductor substrate in each projecting portion of the Schottky metal. 2. The Schottky barrier semiconductor according to claim 1, wherein a second Schottky metal is formed at a tip position facing each other main surface side of the semiconductor substrate in each projecting portion of the Schottky metal. apparatus. In a method for manufacturing a semiconductor device using a semiconductor substrate formed by forming a plurality of semiconductor layers on a base layer,
An initial oxidation step of forming a low concentration semiconductor layer having the same conductivity type by epitaxial growth on the base layer, and forming an insulating protective film on the low concentration semiconductor layer by a thermal oxidation method;
The insulating protective film is selectively etched to open a predetermined portion to expose the surface of the low-concentration semiconductor layer, and a dopant having the same conductivity type as the low-concentration semiconductor layer is formed using the insulating protective film as a mask. By implanting and performing drive diffusion by a thermal diffusion method, an annular first semiconductor layer extending from the surface of the low-concentration semiconductor layer into the layer and reaching the base layer and a plurality of parallel second semiconductor layers Forming a semiconductor layer and forming the second semiconductor layer in a region surrounded by the first semiconductor layer;
All of the insulating protective film is removed by etching, and low concentration semiconductor layers are stacked and formed by epitaxial growth on the surfaces of the first semiconductor layer, the second semiconductor layer, and the low concentration semiconductor layer. A low concentration semiconductor layer stacking step for re-forming the insulating protective film on the concentration semiconductor layer;
The low concentration semiconductor layer and the insulating protective film are selectively etched to form grooves in predetermined portions, sacrificial oxidation is performed on the side and bottom of the grooves, and the insulating protective film is selectively etched again. A window opening step of forming a window in a predetermined portion and exposing the surface of the low concentration semiconductor layer,
By implanting a dopant having a conductivity type different from that of the low-concentration semiconductor layer into the exposed surface of the low-concentration semiconductor layer using the insulating protective film as a mask, and performing drive diffusion by a thermal diffusion method, the low-concentration semiconductor layer A guard ring layer forming step of forming an annular guard ring layer extending from the surface of the substrate into the layer and facing the first semiconductor layer;
The insulating protective film is selectively etched to leave the annular insulating protective film covering from the peripheral edge of the main surface on one side of the semiconductor substrate to the middle of the guard ring layer, and the insulation of the other part. An insulating protective film removing step of removing the protective film to expose the surface of the low-concentration semiconductor layer including the groove and a part of the surface of the guard ring layer;
A Schottky metal is formed by sputtering on one main surface of the semiconductor substrate surrounded by the insulating protective film, and the exposed surfaces of the low-concentration semiconductor layer and the guard ring layer are covered with the Schottky metal, and A peripheral portion of the Schottky metal extends on the insulating protective film, and a projecting portion that forms a part of the Schottky metal is formed in the groove of the low-concentration semiconductor layer to form the second semiconductor layer. A method of manufacturing a Schottky barrier semiconductor device, comprising: a metal forming step of disposing the protrusions between each other and forming a metal electrode on the Schottky metal by sputtering. In a method for manufacturing a semiconductor device using a semiconductor substrate formed by forming a plurality of semiconductor layers on a base layer,
A selective etching removal is performed on the base material of the semiconductor substrate to form an annular first semiconductor layer reaching the base layer from the surface of the base material, and in a region surrounded by the first semiconductor layer, Forming a plurality of second semiconductor layers that are parallel to each other and reach the base layer from the surface of the substrate; and
A low-concentration semiconductor layer having the same conductivity type as the base layer is formed on the base layer, the first semiconductor layer, and the second semiconductor layer by epitaxial growth, and the low-concentration semiconductor layer is selectively etched. And a low concentration semiconductor layer stacking step of forming a plurality of grooves toward the base layer between the second semiconductor layers. In a method for manufacturing a semiconductor device using a semiconductor substrate formed by forming a plurality of semiconductor layers on a base layer,
Doping step of forming a first semiconductor layer doping portion and a second semiconductor layer doping portion by injecting a dopant having the same conductivity type as that of the base layer into a predetermined portion of one main surface of the base layer of the semiconductor substrate When,
A low-concentration semiconductor layer having the same conductivity type as that of the base layer is formed by epitaxial growth on one main surface of the base layer, and the first semiconductor layer doping portion and the second semiconductor layer doping portion are formed. By diffusing the dopant into the low concentration semiconductor layer to a desired position, an annular first semiconductor layer is formed in the low concentration semiconductor layer, and in a region surrounded by the first semiconductor layer. A low-concentration semiconductor layer that forms a plurality of second semiconductor layers parallel to each other and selectively etches the low-concentration semiconductor layer to form a plurality of grooves toward the base layer between the second semiconductor layers A method for manufacturing a Schottky barrier semiconductor device, comprising a stacking step.

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