JP2008187060A - Mesa semiconductor element and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mesa semiconductor element, capable of having a high reliability and stable electrical characteristics and excluding factors containing environmentally hazardous substances, and to provide a method for manufacturing the same. <P>SOLUTION: The mesa semiconductor element 100 capable of excluding the factors, containing the environmentally hazardous substances while securing stability and reliability in electrical characteristics, is obtained by allowing a silicon oxide film 1a coating a slanted side in the mesa section 111 of a semiconductor substrate 102 to contain an Al ions to be charged fixedly and negatively, even if lead or zinc is not doped to the film. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mesa semiconductor device and a method for manufacturing the same, and relates to a technology of pressure resistance, moisture resistance, and chemical resistance of the semiconductor device.

As a conventional mesa type semiconductor element, for example, as shown in FIG. 3, there is one in which an inclined side surface forming a mesa portion of a semiconductor substrate is covered with a resin containing glass particles.
In FIG. 3, 101 is a diode, 102 is a semiconductor substrate, 103 is an anode electrode, 104 is a cathode electrode, 105 is a protective film, 106 is a P-type semiconductor region, 107 is an N ⁻ type semiconductor region, and 108 is an N ⁺ type semiconductor region. , 109 is one main surface of the semiconductor substrate, 110 is the other main surface of the semiconductor substrate, 111 is an inclined side surface, 112 is a PN junction, 113 is an insulating resin, and 114 is a glass particle.

Diode 101 consisting of the mesa type semiconductor device is made by forming a plurality of semiconductor crystal thin film semiconductor body 102 forms an epitaxial layer on the upper surface of the high-concentration N ⁺ -type semiconductor region 108 of the first layer, the N ⁺ -type semiconductor A second layer low concentration N ⁻ type semiconductor region 107 having the same conductivity type is formed on the upper surface of the region 108, and a third layer P type semiconductor region 106 having a different conductivity type is formed on the upper surface of the N ⁻ type semiconductor region 107. The N ⁻ type semiconductor region 107 and the P type semiconductor region 106 form a PN junction 112.

An anode electrode 103 is formed on the upper surface of the P-type semiconductor region 106 that forms one main surface 109 of the semiconductor substrate 102, and a cathode electrode 104 is formed on the lower surface of the N ⁺ -type semiconductor region 108 that forms the other main surface 110 of the semiconductor substrate 102. Forming. The semiconductor substrate 102 is formed with a mesa portion 111 having a concave inclined side surface, and a protective film 105 is formed covering the mesa portion 111. The protective film 105 is made of an insulating resin 113 such as epoxy containing glass particles 114.

According to this configuration, since the protective film 105 covering the mesa unit 111 includes the negatively charged glass particles 114, it is possible to obtain stable pressure resistance due to the negative charges of the glass particles 114, and the glass Since the heat treatment for curing the insulating resin 113 can be performed at a low temperature as compared with the temperature for forming the normal protective film made of, the degree of freedom of the manufacturing process can be increased. There exists patent document 1 as a prior art document.
JP 2001-110799 A

However, in the conventional configuration, since the protective film 105 is made of a resin, there is a problem that the moisture resistance and chemical resistance are inferior and the reliability is lowered.
In addition, the distribution of the glass particles 114 in the protective film 105 is required to be uniform, but when non-uniformity occurs, the electrical characteristics in the reverse direction including the withstand voltage and the mobile ions that the resin originally has are not uniform. Since the effect of canceling the influence is hindered, there is a problem that causes problems such as instability of electric characteristics.

Moreover, in order to make the glass particles 114 have a negative charge, the glass particles 114 have a problem that they must contain an environmentally hazardous substance such as lead or zinc.
The present invention solves the above-mentioned problems, has a moisture and chemical resistance, can obtain a stable negative charge, and has a protective film that does not contain environmentally hazardous substances such as lead and zinc. It is an object of the present invention to provide a mesa semiconductor device having excellent reliability and stable electrical characteristics and a method for manufacturing the mesa semiconductor device.

  In order to solve the above-described problems, a mesa semiconductor device according to the present invention is a semiconductor device having a mesa-shaped semiconductor substrate, which covers a slanted side surface forming a mesa portion of the semiconductor substrate and contains Al ions. An oxide film is formed.

  The mesa type semiconductor device of the present invention is a semiconductor device having a mesa-shaped semiconductor substrate, and covers one or more ions of Al, Cl, and F covering an inclined side surface forming a mesa portion of the semiconductor substrate. A silicon oxide film containing is formed.

  According to the method of manufacturing a mesa semiconductor device of the present invention, in a mesa-shaped semiconductor substrate, a silicon oxide film is formed by covering an inclined side surface forming a mesa portion, and Al is ion-implanted into the silicon oxide film to form the silicon oxide film. The film is a silicon oxide film containing Al ions.

  According to the method of manufacturing a mesa type semiconductor element of the present invention, a silicon oxide film is formed by covering an inclined side surface forming a mesa portion in a mesa-shaped semiconductor substrate, and any one of Al, Cl, and F is formed on the silicon oxide film. Alternatively, a plurality of types of ions are implanted, and the silicon oxide film is made of a silicon oxide film containing any one kind or a plurality of kinds of ions of Al, Cl, and F.

  According to the method of manufacturing a mesa semiconductor device of the present invention, a low-concentration semiconductor region of the second layer having the same conductivity type is formed by epitaxial growth on a high-concentration semiconductor region of the first layer made of silicon, and the low-concentration semiconductor region A semiconductor layer of the third layer is formed by diffusing dopants of different conductivity types from the surface of the semiconductor layer into the layer, and an interface between the semiconductor region of the third layer and the low-concentration semiconductor region of the second layer is used as a semiconductor junction surface Semiconductor substrate forming step of forming a semiconductor substrate, and mesa etching along the outer periphery of one main surface of the semiconductor substrate and reaching the high-concentration semiconductor region, and an inclination forming a mesa portion on the outer periphery of the semiconductor substrate A silicon oxide film is formed from one main surface of the semiconductor substrate to the inclined side surface by a mesa forming step of forming a side surface to make the semiconductor substrate into a mesa shape and a thermal oxidation method. A silicon oxide film corresponding to one main surface of the semiconductor substrate is covered with a mask, Al ions are implanted into the silicon oxide film on the inclined side surface, and Al ions are included on the inclined side surface. An ion implantation step of forming a silicon oxide film, and selective etching removal of the silicon oxide film to expose the semiconductor region of the third layer that forms one main surface of the semiconductor substrate; Forming an anode electrode extending from the surface of the semiconductor region to the periphery of the silicon oxide film, grinding and polishing the high-concentration semiconductor region forming the other main surface of the semiconductor substrate, and adjusting the thickness; Forming a cathode electrode on the surface of the substrate.

  As described above, according to the present invention, the silicon oxide film formed on the inclined side surface forming the mesa portion of the mesa-shaped semiconductor substrate contains at least one of Al, Cl, and F ions, so that the fixed Therefore, a stable electrical characteristic can be secured. Moreover, since what covers the inclined side surface of the semiconductor substrate is a silicon oxide film, it can be excellent in moisture resistance and chemical resistance, and a semiconductor element having excellent reliability can be obtained. Furthermore, since elements such as lead and zinc are not added to the silicon oxide film, elements including environmentally hazardous substances can be excluded.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a mesa semiconductor device according to an embodiment of the present invention. The same components as those described in FIG.

  In FIG. 1, 1 is a silicon oxide film, 1a is a silicon oxide film containing Al ions, 3 is one main surface of a semiconductor substrate, 4 is the other main surface of the semiconductor substrate, and 100 is a mesa semiconductor element. .

  As shown in FIG. 1, the silicon oxide film 1 extends from the peripheral portion of the surface of the P-type semiconductor region 106, which is one main surface 3 of the semiconductor substrate 102, to the region above the mesa portion 111 that forms the inclined side surface of the semiconductor substrate 102. In particular, the portion covering the inclined side surface of the mesa 111 is made of the silicon oxide film 1a containing Al ions that are negatively charged.

  In this configuration, the PN junction 112 exposed on the inclined side surface of the mesa portion 111 is an element that greatly affects the element characteristics such as pressure resistance. By covering the mesa portion 111 with the silicon oxide film 1a containing Al ions, the PN junction is covered. 112 is less susceptible to external influences, and a mesa type semiconductor device that can improve reliability and have stable pressure resistance by including Al ions without including environmentally hazardous substances such as lead and zinc as in the prior art. Can be realized. Moreover, the silicon oxide film 1a can be excellent in moisture resistance and chemical resistance due to the characteristics of silicon.

The mesa portion 111 may be more strongly protected by forming a silicon oxide film on the silicon oxide film 1a containing Al ions formed on the mesa portion 111.
In the present embodiment, the semiconductor substrate 102 is formed of the N ⁺ type semiconductor region 108, the N ⁻ type semiconductor region 107, and the P type semiconductor region 106, and the P type semiconductor region 106 and the N ⁻ type semiconductor region 107. The diode having the PN junction 112 as an interface has been described as an example. However, the present invention is not limited to the configuration described above, and can be applied to general semiconductor elements such as transistors as long as a withstand voltage structure is obtained using a semiconductor substrate having a mesa shape.

  Further, although the mesa portion 111 is covered with the silicon oxide film 1a containing Al ions, the same effect can be obtained by using a silicon oxide film containing Cl ions or F ions instead of Al ions.

A method for manufacturing the mesa semiconductor device 100 of the present invention will be described below. 2A to 2E show main process end points in the manufacturing process of the mesa semiconductor device 100. FIG. In FIG. 2, 1 is a silicon oxide film, 1a is a silicon oxide film containing Al ions, 2 is a mask, 3 is one main surface of the semiconductor substrate, 4 is the other main surface of the semiconductor substrate, 102 is a semiconductor substrate, 103 Denotes an anode electrode, 104 denotes a cathode electrode, 106 denotes a P-type semiconductor region, 107 denotes an N ⁻ type semiconductor region, 108 denotes an N ⁺ type semiconductor region, 111 denotes an inclined side surface, and 112 denotes a PN junction.

FIG. 2A shows a semiconductor substrate forming step, and a second layer low concentration N having the same conductivity type is formed on the first layer high concentration N ⁺ type semiconductor region 108 made of silicon by epitaxial growth. ^{A −} type semiconductor region 107 is formed, and a P type dopant is diffused from the surface of the N ⁻ type semiconductor region 107 into the layer to form a third layer P type semiconductor region 106 having different conductivity types. The semiconductor substrate 102 is formed with the interface between the region 106 and the N ⁻ type semiconductor region 107 as a PN junction 112 which is a semiconductor junction surface.

Hereinafter, the surface of the P-type semiconductor region 106 of the semiconductor substrate 102 is defined as one main surface 3 of the semiconductor substrate 102, and the surface of the N ⁺ -type semiconductor region 108 opposite to the main surface 3 is the surface of the semiconductor substrate 102. The other main surface 4 is used.

FIG. 2B shows a mesa formation process. After the previous semiconductor substrate formation process, a side surface that reaches the N ⁺ type semiconductor region 108 along the outer periphery of one main surface 3 of the semiconductor substrate 102. Mesa etching is performed to form inclined mesa portions 111 on the outer periphery of the semiconductor substrate 102 to make the semiconductor substrate 102 a mesa shape.

  FIG. 2 (c) shows an oxide film forming step. After the previous mesa forming step, silicon is applied to one main surface 3 of the semiconductor substrate 102 and the mesa portion 111 forming the inclined side surface by thermal oxidation. An oxide film 1 is formed.

Here, as a method of forming the silicon oxide film, thermal CVD or plasma CVD may be used in addition to the thermal oxidation method.
FIG. 2D shows an ion implantation process. After the previous oxide film forming process, the silicon oxide film 1 corresponding to one main surface 3 of the semiconductor substrate 102 is covered with a mask 2, and the silicon oxide film 1 is formed. Among them, Al is ion-implanted only into the portion formed in the mesa portion 111 having the inclined side surface, and the silicon oxide film 1 a containing Al ions is formed on the mesa portion 111.

  As described above, conventionally, it has been difficult to ensure a uniform distribution of the glass particles in the protective film, which may cause inconveniences such as unstable electrical characteristics. However, in this embodiment, by performing ion implantation, Al ions can be reliably distributed uniformly in the layer of the silicon oxide film 1a, and variations in reverse electrical characteristics including breakdown voltage can be eliminated. The mesa type semiconductor device 100 can be realized without inconveniences such as unstable electrical characteristics.

  Here, heat treatment may be performed after ion implantation and annealing may be performed to improve the film quality of the silicon oxide film 1a containing Al ions and to activate the charge. Further, a silicon oxide film may be further formed on the silicon oxide film 1a containing Al ions by the above-described method to improve the reliability as a protective film.

The irradiation angle of ion implantation is not particularly limited, but irradiation may be performed in an oblique direction in accordance with the inclined surface of the mesa unit 111. According to this, the irradiation efficiency of ion implantation can be increased.
FIG. 2E shows an electrode formation process. After the previous ion implantation process, the silicon oxide film 1 is selectively etched away to form a P-type semiconductor region which is one main surface 3 of the semiconductor substrate 102. 106 is exposed and an anode electrode made of Al or the like extending from the surface of the P-type semiconductor region 106 to the periphery of the silicon oxide film 1 is formed. Then, the N ⁺ type semiconductor region 108 which is the other main surface 4 of the semiconductor substrate 102 is ground and polished to adjust the thickness, and the surface of the N ⁺ type semiconductor region 108 is a multilayer or single layer having gold, silver or the like as the outermost surface. By forming the cathode electrode 104, the mesa type semiconductor element shown in FIG. 1 is obtained.

  Here, as an example, a manufacturing process in which the silicon oxide film 1 is selectively etched and removed after the ion implantation is performed. However, the silicon oxide film 1 is selectively etched and removed before the ion implantation, and the mask 2 is covered with the ion implantation. May be applied.

In the present embodiment, the semiconductor substrate 102 is formed of the N ⁺ type semiconductor region 108, the N ⁻ type semiconductor region 107, and the P type semiconductor region 106, and the P type semiconductor region 106 and the N ⁻ type semiconductor region 107. Although the diode having the PN junction 112 as an example has been described, it is also possible to carry out by exchanging both conductivity types. In that case, the anode electrode and the cathode electrode are also exchanged.

  The present invention is useful as a mesa-type semiconductor device, and is particularly suitable for a device that is electrically stable and requires reliability without containing an environmental load substance.

Sectional drawing of the mesa type semiconductor element in embodiment of this invention Sectional drawing which shows the manufacturing process of the mesa type semiconductor element in embodiment of this invention Sectional view of a conventional semiconductor device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon oxide film 1a Silicon oxide film containing Al ion 2 Mask 3 One main surface of a semiconductor substrate 4 The other main surface 100 of a semiconductor substrate 100 Mesa type semiconductor element 101 Diode 102 Semiconductor substrate 103 Anode electrode 104 Cathode electrode 105 Protective film 106 P-type semiconductor region 107 N ⁻ -type semiconductor region 108 N ⁺ -type semiconductor region 109 One main surface 110 of the semiconductor substrate The other main surface 111 of the semiconductor substrate 111 Mesa portion 112 PN junction 113 Insulating resin 114 Glass particles

Claims (5)

A semiconductor device having a mesa-shaped semiconductor substrate, wherein a silicon oxide film containing Al ions is formed by covering an inclined side surface forming a mesa portion of the semiconductor substrate. A semiconductor element having a mesa-shaped semiconductor substrate, and a silicon oxide film containing any one kind or plural kinds of ions of Al, Cl, F is formed by covering an inclined side surface forming a mesa portion of the semiconductor body. Mesa type semiconductor device characterized by the above. In a mesa-shaped semiconductor substrate, a silicon oxide film is formed by covering the inclined side surface forming the mesa portion, and Al is ion-implanted into the silicon oxide film so that the silicon oxide film becomes a silicon oxide film containing Al ions. A method for manufacturing a mesa semiconductor element. In a mesa-shaped semiconductor substrate, a silicon oxide film is formed by covering an inclined side surface forming a mesa portion, and one or more of Al, Cl, and F are ion-implanted into the silicon oxide film, and the silicon oxide film Is a silicon oxide film containing any one kind or plural kinds of ions of Al, Cl and F. A second low-concentration semiconductor region having the same conductivity type is formed on the high-concentration semiconductor region of the first layer made of silicon by epitaxial growth, and dopants of different conductivity types are formed from the surface of the low-concentration semiconductor region into the layer. A semiconductor substrate forming step of forming a semiconductor region of a third layer by diffusing, and forming a semiconductor substrate with an interface between the semiconductor region of the third layer and the low concentration semiconductor region of the second layer as a semiconductor bonding surface;
A mesa-etched side surface that reaches the high-concentration semiconductor region along the outer periphery of one main surface of the semiconductor substrate to form an inclined side surface that forms a mesa portion on the outer periphery of the semiconductor substrate, thereby forming the semiconductor substrate in a mesa shape Nassus mesa formation process,
An oxide film forming step of forming a silicon oxide film from one main surface of the semiconductor substrate to the inclined side surface by a thermal oxidation method;
A silicon oxide film corresponding to one main surface of the semiconductor substrate is covered with a mask, and Al is ion-implanted into the silicon oxide film on the inclined side surface to form a silicon oxide film containing Al ions on the inclined side surface. An ion implantation process;
The silicon oxide film is selectively etched away to expose the third layer semiconductor region that forms one main surface of the semiconductor substrate, and from the surface of the third layer semiconductor region to the periphery of the silicon oxide film Forming an anode electrode extending to the surface, adjusting the thickness by grinding and polishing the high-concentration semiconductor region that forms the other main surface of the semiconductor substrate, and forming an electrode that forms a cathode electrode on the surface of the high-concentration semiconductor region A method for manufacturing a mesa semiconductor element.

Images