JP3339549B2 - Glass-coated semiconductor device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass-coated semiconductor device and a method of manufacturing the same, and more particularly, to a glass-coated semiconductor in which uniform and high-quality electrodes are formed and a pn junction is coated with glass containing a metal oxide. The present invention relates to an apparatus and a method for manufacturing the same.

[0002]

2. Description of the Related Art A mesa type semiconductor device (at least one p
A semiconductor device in which a groove is formed by etching from the main surface at the n-junction and the pn junction is exposed on the side wall of the groove)
Various techniques for forming a high-quality electrode by plating have been conventionally proposed.

As a prior art of this kind, a technique relating to electroless plating of a mesa type semiconductor device is disclosed in, for example, Japanese Patent Application Laid-Open No. Sho.
It is known as described in JP-A-6-58232. According to this conventional technique, in a method of forming an electrode of a semiconductor device in which the inner wall of a mesa groove is covered with glass, a resist is applied to a mesa groove provided on one main surface, and the other main surface is partially electrolessly plated by electroless plating. One electrode is formed, a second electrode is formed on the entire surface of the other main surface by electroless plating, and then the mesa groove formed on one main surface is covered with glass. The warp of the formed wafer can be reduced.

Further, as another conventional technique for electroless nickel plating on a silicon substrate surface, for example, Japanese Patent Laid-Open No. 1-1
A technique described in Japanese Patent No. 85920 is known. In this prior art, first, a first plating film is formed using an alkaline nickel-phosphorus plating bath, then a second plating film having a different film quality is formed, and then etching for forming a bond is performed. Thus, the problem of deterioration of the semiconductor element due to stress can be solved.

Further, as another conventional technique for applying metal plating to the upper part of a mesa of a mesa type semiconductor device, for example, a technique described in Japanese Patent Application Laid-Open No. 1-223219 is known. In this conventional technique, a photoresist is formed on an upper portion of a mesa portion, a central portion of the photoresist is opened, a metal plating is applied to the opening, and then the photoresist is removed and an additional metal plating is applied. In addition, it is possible to solve problems such as generation of sagging around the metal electrode.

[0006]

However, in the prior art described in Japanese Patent Application Laid-Open No. 56-58232, the surface protection film is formed after the first electrode and the second electrode are formed by electroless plating. Since the glass is coated, the warpage of the wafer can be reduced, but the temperature and atmosphere of firing the glass are limited, and it is difficult to obtain a semiconductor device with high withstand voltage and low leakage current. Have.

In the prior art described in Japanese Patent Laid-Open No. 1-185920, since the first plating film and the second plating film are formed and then etched to form a junction, the conventional technology is not disclosed. As in the technique described in Japanese Patent Application Laid-Open No. 56-58232, there is a problem that it is difficult to obtain a semiconductor device having a high breakdown voltage and a low leakage current.

Further, the above-mentioned Japanese Patent Application Laid-Open No. 1-223719
Since the prior art described in Japanese Patent Application Laid-Open Publication No. H11-209550 includes a process of forming and processing a photoresist on the upper portion of the mesa portion and the side wall portion of the mesa portion, it is difficult to uniformly apply the photoresist,
There is a problem that it is difficult to uniformly plate the metal electrode only on the central portion of the upper portion of the mesa portion.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide a uniform and high-quality electroless electro-mechanical electrode of a mesa semiconductor device whose mesa portion is covered with glass containing a metal oxide. A glass-coated semiconductor device formed by nickel plating and a method for manufacturing the same.

[0010]

According to the present invention, the object is to form a pn junction by diffusing impurities of the opposite conductivity type from one main surface of a semiconductor substrate having a pair of main surfaces. A mesa-shaped groove is provided so that a pn junction is exposed in a predetermined region from one main surface, and a glass containing a metal oxide (lead-based glass made of lead oxide, silicon dioxide, alumina, or oxidized oxide) is formed in the mesa portion. In a glass-coated semiconductor device on which a zinc-based glass comprising zinc, silicon dioxide, and boron oxide) film is formed,
The glass reduced film, in which the metal oxide in the glass coating is reduced and the metal of the metal oxide is discharged out of the glass, has a thickness of 1 nm to 3 nm.
This is achieved by providing a micrometer thickness.

Another object of the present invention is to form a pn junction by diffusing impurities of the opposite conductivity type from one main surface of a semiconductor substrate having a pair of main surfaces and forming a pn junction from the one main surface to a predetermined region. In a method of manufacturing a glass-coated semiconductor device in which a mesa-shaped groove is provided so that a pn junction is exposed, and a glass film containing a metal oxide is formed in the mesa portion, the glass film is formed after forming the glass film. Or a step of forming a glass reduced film in which the metal oxide in the glass coating is reduced by annealing in a gas containing hydrogen to discharge the metal of the metal oxide out of the glass, and a mixed solution of hydrofluoric acid and nitric acid Immersing the semiconductor substrate in an aqueous solution of dilute hydrofluoric acid and palladium chloride to clean the semiconductor surface not covered with the glass coating; In the step of catalyzing the semiconductor surface not covered, it is achieved by including a step of performing electroless nickel plating by immersing the entire semiconductor substrate to the plating solution.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a glass-coated semiconductor device and a method of manufacturing the same according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view illustrating the structure of a glass-coated semiconductor device according to a first embodiment of the present invention, and FIG.
FIG. 3 is a plan view of the glass-coated semiconductor device shown in FIG. 1 and 2, 1 is an n-type semiconductor region, 2 is a p + type semiconductor region, 3 is an n + type semiconductor region,
Is a glass coating, 8 is a pn junction, 20 is an anode electrode, 3
0 is a cathode electrode and 51 is a glass reduction film.

As shown in FIGS. 1 and 2, a glass-coated semiconductor device according to a first embodiment of the present invention has a p + -type semiconductor region 2 having a high impurity concentration on one main surface of an n-type semiconductor substrate.
Is formed, an n + -type semiconductor region 3 having a high impurity concentration is formed on the other main surface, and p +
A mesa groove is provided so that the n-junction 8 is exposed, and a glass coating 5 and a glass reduction film 51 not containing a glass component metal are sequentially formed on the mesa portion, and the n-type semiconductor substrate forms the n-type semiconductor region 1. It is configured. In the illustrated semiconductor device, an anode electrode 20 is provided in the p + -type semiconductor region 2 serving as an anode layer, and a cathode electrode 30 is provided in ohmic contact with the n + -type semiconductor region 3 serving as a cathode layer.

The glass-coated semiconductor device according to the first embodiment of the present invention does not include a glass component metal around the anode electrode 20, as shown in a plan view of FIG. It has a structure in which a glass reduction film 51 as an insulating film is arranged, and further has a pn junction 8 formed by an n-type semiconductor region 1 as a first semiconductor region and a p + -type semiconductor region 2 as a second semiconductor region. Are formed around the anode electrode 20. In FIG. 2, a schematic cross-sectional view of a portion indicated by AA ′ corresponds to FIG.

The glass-coated semiconductor device according to the first embodiment of the present invention shown in FIGS. 1 and 2 has a structure in which, when electroless nickel plating is performed, n + as the second semiconductor region 2 and the third semiconductor region. Electroless nickel plating can be uniformly performed on each surface of the mold semiconductor region 3 with good adhesion, and an effect that nickel plating is not performed on the glass coating 5 can be obtained.

That is, in the semiconductor device shown in FIGS. 1 and 2, the anode electrode 20 and the cathode electrode 30 form the glass coating 5 and then form the glass reduction film 51 containing no glass component metal. It is formed by performing electrolytic nickel plating. Thereby, the electrodes 20 and 30 can be formed by uniformly applying electroless nickel plating to the surfaces of the second semiconductor region 2 and the third semiconductor region 3 with good adhesion. However, in this case, the glass reduced film 5 formed on the glass film 5
No nickel plating is formed on 1. The reason is that the metal oxide of the glass component has a catalytic action on the plating, but the glass reduction film 51 containing no metal of the glass component on the glass coating 5 as in the first embodiment of the present invention. This is because the metal oxide having a catalytic action on plating is not contained in the glass reduced film 51.

FIGS. 3A to 3C are cross-sectional views showing main steps for explaining a method of manufacturing the glass-coated semiconductor device according to the first embodiment of the present invention described above. Will be described.

(1) As the silicon substrate to be the n-type semiconductor region 1, the specific resistance of CZ (111) is 35Ωcm to 45Ω.
An n-type silicon substrate having a surface impurity concentration of 1 × 10 ¹⁹ / cm ² or more is prepared on one main surface.
B (boron) is implanted to a depth of 40 ± 5 μm by ion implantation or thermal diffusion using boron nitride as a diffusion source to form a p + -type semiconductor region 2, and then a surface impurity is formed on the other main surface. An ion implantation method of P (phosphorus) to a depth of 45 ± 10 μm or a thermal diffusion method using phosphorus hypochlorite as a diffusion source so that the concentration becomes 1 × 10 ²⁰ / cm ² or more, and n + type. After the formation of the semiconductor region 3, silicon oxide films 6a and 6b having a thickness of about 2 μm to 3 μm are formed by dry oxidation or wet oxidation (FIG. 3A).

(2) Next, after a part of the silicon oxide film 6a on one main surface is removed by ordinary photolithography, the remaining silicon oxide film 6a is used as an etching mask, and the U01 etchant is used. 60 μm
Then, a mesa groove 9 is formed so that a pn junction between the p + -type semiconductor region 2 and the n-type semiconductor region 1 is exposed by etching to a depth of FIG. 3 (FIG. 3B).

(3) The silicon oxide films 6a and 6b used as an etching mask in the step of FIG. 3B are removed with an acid containing HF, and paste-like lead-based glass (main component: PbO , SiO ₂ , Al ₂ O ₃ ) or zinc-based glass (main components: ZnO, SiO ₂ , B ₂ O)
₃ ) is applied at 55 ± 10 μm and heat treated at 700 ° C. to 850 ° C. for 40 minutes in an oxygen atmosphere as a glass baking treatment to form a glass film 5 (FIG. 3C).

(4) Thereafter, a metal-free glass reduction film 51 in the glass coating 5 is formed to a thickness of about 1 nanometer to 3 micrometers. This glass reduction film 51
Is formed by forming a glass film 5 and then annealing in hydrogen or a gas containing hydrogen at 620 ± 50 ° C. to reduce the metal oxide of the glass component and discharge the metal of the metal oxide out of the glass. be able to. The metal oxide of the glass component is PbO for lead-based glass and ZnO for zinc-based glass, and the metal is metal lead or metal zinc (FIG. 3D).

(5) Thereafter, the semiconductor substrate is immersed in a mixed solution of hydrofluoric acid and nitric acid to clean the semiconductor surface, and further immersed in an aqueous solution of diluted hydrofluoric acid and palladium chloride. Then, a catalytic treatment is performed on the nickel plating, and electroless nickel plating is performed in a solution containing nickel chloride using sodium hypophosphite as a reducing agent. Thus, the anode electrode 20 and the cathode electrode 30 are formed on the surfaces of the p + -type semiconductor region 2 and the n + -type semiconductor region 3 by nickel plating. Next, by dicing the central portion of the fired glass coating 5 along the cutting line 10, a semiconductor pellet is completed, and the glass-coated semiconductor device shown in FIG. 1 is obtained [FIG. 3 (e)].

In the method for fabricating a semiconductor device according to the embodiment of the present invention, the presence of the glass reduced film 51 containing no metal oxide or metal prevents the surface of the glass film 5 from being nickel-plated, and The surface of each of the semiconductor region 2 and the n @ + -type semiconductor region 3 can be subjected to extremely excellent selective electroless plating in which electroless nickel plating is uniformly applied with good adhesion.

FIG. 4 is a sectional view illustrating the structure of a glass-coated semiconductor device according to a second embodiment of the present invention. FIG.
In the figure, reference numeral 7 denotes an insulating film, and other reference numerals are the same as those in FIG.

The glass-coated semiconductor device according to the second embodiment of the present invention shown in FIG. 4 is similar to the glass-coated semiconductor device according to the first embodiment of the present invention described with reference to FIGS. Insulating film 7 such as a silicon oxide film between the surface of n-type semiconductor region 2 and n-type semiconductor region 1
Is formed. Such a second aspect of the present invention
In the first embodiment, the addition of the insulating film 7 made of a silicon oxide film or the like makes it possible to reduce the interface state on the semiconductor surface, and to reduce the surface generated current flowing on the semiconductor surface.

FIG. 5 is a sectional view illustrating the structure of a glass-coated semiconductor device according to a third embodiment of the present invention. FIG.
In the figure, reference numeral 4 denotes an n @ + type semiconductor region, and other reference numerals are the same as those in FIG.

The glass-coated semiconductor device according to the third embodiment of the present invention shown in FIG. 5 has p + around the chip of the glass-coated semiconductor device according to the first embodiment of the present invention described with reference to FIGS. A high impurity concentration n + type semiconductor region 4 is formed adjacent to the n type semiconductor region 1 so as to surround the type semiconductor region 2. Such a glass-coated semiconductor device according to the third embodiment of the present invention has a main pn
Not only can the depletion layer extending from the junction be prevented from extending to the chip end to prevent an increase in leakage current, but also the glass does not need to be cut during dicing,
It is possible to reduce the withstand voltage failure due to the occurrence of cracks in the glass.

FIG. 6 is a cross-sectional view for explaining the structure of a glass-coated semiconductor device according to a fourth embodiment of the present invention. The reference numerals in FIG. 6 are the same as those in FIGS.

The glass-coated semiconductor device according to the third embodiment of the present invention shown in FIG. 6 is different from the glass-coated semiconductor device according to the first embodiment of the present invention described with reference to FIGS.
High impurity concentration n @ + -type semiconductor region 4 described with reference to FIG.
And the silicon oxide film 7 described with reference to FIG. According to the fourth embodiment of the present invention, it is possible to prevent an increase in leak current due to the depletion layer extending from the main pn junction extending to the end of the chip, and it is not necessary to cut the glass at the time of dicing. This has the effect of reducing the withstand voltage failure due to the generation of cracks, and further, it is possible to reduce the interface state on the semiconductor surface, and it is possible to reduce the surface generation current flowing on the semiconductor surface.

The glass-coated semiconductor device according to each of the above-described embodiments of the present invention has a PbO—SiO
_{Although the} description has been made assuming that a lead-based glass made of _2- Al ₂ O ₃ is used, the present invention is not limited to the above-described lead-based glass as a glass coating, and PbO in which the above-described Al ₂ O ₃ is replaced with B ₂ O ₃ is used.
Lead-based glass composed of —SiO ₂ —B ₂ O ₃ , Al ₂ O ₃ and B ₂
O ₃ PbO-SiO ₂ of the 4-component system containing -Al ₂ O ₃ -B
_The present invention can also be applied to the case where a ₂ O ₃ -based lead glass is used.

Further, the glass-coated semiconductor device according to each of the above-described embodiments of the present invention has a glass coating of ZnO.
Although it has been described that a zinc-based glass of —B ₂ O ₃ —SiO ₂ system can be used, the present invention is not limited to the above-described zinc-based glass as a glass coating, and PbO and ZnO may be used as the metal oxide described above. can be applied to a case of using a glass comprising Al ₂ O ₃ or B ₂ O ₃ in the lead-zinc glass and the lead-zinc glass of PbO-ZnO-SiO ₂ system comprising.

As described above, according to the glass-coated semiconductor device and the method of manufacturing the same according to the embodiments of the present invention, a lead-based glass coating or a zinc-based glass coating is used as a surface stabilizing film, and electroless nickel plating is used. Electrodes can be uniformly and densely formed in the wafer in ohmic contact with the semiconductor region with good adhesion, the subsequent wettability with solder can be extremely good, and high withstand voltage and high reliability can be obtained. A glass-coated semiconductor device can be obtained, and
Such a semiconductor device can be manufactured with high yield.

The withstand voltage of the glass-coated semiconductor device according to the embodiment of the present invention is about 800 ± 100 V, and the leakage current can be reduced to 10 nA or less when the reverse direction applied voltage is 400 V. An excellent glass-coated semiconductor device and a method for manufacturing the same were obtained. Furthermore, a high temperature reverse bias test (DC 400 V, junction temperature 1
(50 ° C., 1000 h), the leakage current was increased by only 50% of the initial value, and high reliability was obtained.

[0035]

As described above, according to the present invention, an electrode of a mesa semiconductor device covered with glass containing a metal oxide is formed by uniform and high quality electroless nickel plating, A highly reliable glass-coated semiconductor device can be provided, and electrodes formed by electroless nickel plating can be formed uniformly, densely, and in ohmic contact with a semiconductor region in a wafer with good adhesion.
It is possible to provide a manufacturing method capable of making the subsequent wettability with solder extremely good.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a glass-coated semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a plan view of the glass-coated semiconductor device shown in FIG. 1 as viewed from one main surface.

FIGS. 3A to 3C are cross-sectional views illustrating main steps of a method for manufacturing the glass-coated semiconductor device according to the first embodiment of the present invention. FIGS.

FIG. 4 is a cross-sectional view illustrating a structure of a glass-coated semiconductor device according to a second embodiment of the present invention.

FIG. 5 is a sectional view illustrating a structure of a glass-coated semiconductor device according to a third embodiment of the present invention.

FIG. 6 is a sectional view illustrating a structure of a glass-coated semiconductor device according to a fourth embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 n-type semiconductor region 2 p + -type semiconductor region 3, 4 n + -type semiconductor region 5 glass coating 6 a, 6 b silicon oxide film 7 insulating film 8 pn junction end 9 etching region 10 pelletizing line 20 anode electrode 30 cathodic Electrode 51 Glass reduction film

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hitoshi Matsuzaki 3-1-1 Sachimachi, Hitachi-shi, Ibaraki Hitachi, Ltd. Inside Hitachi Plant (72) Inventor Minoru Sugano 3-chome Bentencho, Hitachi-shi, Ibaraki No. 2 Tachiharacho Electronics Co., Ltd. (56) References JP-A-9-246571 (JP, A) JP-A-53-96765 (JP, A) JP-A-57-79618 (JP, A) 1986-226931 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/312 H01L 21/314 H01L 21/316 H01L 21/318 H01L 23/30 H01L 29/861

Claims (6)

(57) [Claims] 1. A semiconductor substrate having a pair of main surfaces, an impurity of a conductivity type opposite to that of the substrate is diffused from one of the main surfaces to form a pn.
A junction is formed, and p
In a glass-coated semiconductor device in which a mesa-shaped groove is provided so that an n-junction is exposed, and a glass film containing a metal oxide is formed in the mesa portion, the metal oxide in the glass film is formed on the surface of the glass film. A glass-coated semiconductor device provided with a glass reduction film that reduces and discharges metal of a metal oxide out of glass. 2. The glass coating according to claim 1, wherein the glass coating is a lead-based glass made of lead oxide, silicon dioxide, and alumina, or a zinc-based glass made of zinc oxide, silicon dioxide, and boron oxide. Glass-coated semiconductor device. 3. The glass-coated semiconductor device according to claim 1, wherein the thickness of the glass reduction film is 1 nm to 3 μm. 4. A semiconductor substrate having a pair of main surfaces, wherein impurities of the opposite conductivity type are diffused from one main surface of the semiconductor substrate to form a pn.
A junction is formed, and p
In a method of manufacturing a glass-coated semiconductor device in which a mesa-shaped groove is provided so that an n-junction is exposed, and a glass film containing a metal oxide is formed in the mesa portion, after forming the glass film, A step of forming a glass reduced film in which the metal oxide is reduced and the metal of the metal oxide is discharged out of the glass, a step of cleaning a semiconductor surface not covered with the glass coating, and a step of cleaning the semiconductor surface which is not coated with the glass coating. A method for producing a glass-coated semiconductor device, comprising: a step of catalyzing a non-existent semiconductor surface; and a step of dipping the entire semiconductor substrate in a plating solution to perform electroless nickel plating. 5. The step of cleaning the semiconductor surface is performed by immersing a semiconductor substrate in a mixed solution of hydrofluoric acid and nitric acid, and the step of catalyzing the semiconductor surface is performed by diluting hydrofluoric acid with dilute hydrofluoric acid. The method according to claim 4, wherein the method is performed by immersing the semiconductor substrate in an aqueous solution of palladium chloride. Forming a wherein said glass reducing film, method of manufacturing a glass-covered semiconductor device according to claim 4 or 5, wherein it is a process of annealing the glass coated with a gas containing hydrogen or hydrogen .