JP2000004031A - Two-terminal surge protective element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a current breakdown amount of a surge protective element for protecting a communication circuit system from an overvoltage or an overcurrent such as thunder surge or switching surge. SOLUTION: In a two-terminal surge protective element, second conductivity- type base regions 3 and 4 and first conductivity-type emitter regions 5 and 6 are formed on both faces of a first conductivity-type semiconductor substrate 2 as a common substrate, and each exposed face of the base regions 3 and 4 and emitter regions 5 and 6 is short-circuited with respective metal electrode 9 or 10. In addition, refractory metal films 11 and 12 are formed in contact with the exposed faces of the base regions 3 and 4 and of the emitter regions 5 and 6, and the electrodes for low-resistance metal films 13 and 14 are formed on the refractory metal films 11 and 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a two-terminal surge protection device for protecting a communication equipment circuit system from overvoltage and overcurrent such as lightning surge or switching surge.

[0002]

2. Description of the Related Art Two-terminal surge protection devices are widely used for various purposes such as lightning surge protection in communication lines and the like. There is an increasing demand for a miniaturized element having a high surge current resistance without increasing the element size of the surge protection element.

FIG. 4 shows an example of the structure of a conventional two-terminal surge protection device. FIG. 4 (a) is a plan view and FIG. 4 (b) is a sectional view. In FIG. 4, 1 is a semiconductor chip,
Reference numeral 2 denotes an N-type or P-type conductive semiconductor substrate, and 3 and 4 denote P-type or N-type conductive base diffusion portions provided on both surfaces of the semiconductor substrate 2; Type or P type conductivity type emitter diffusion portions, 7 and 8 are insulating films formed of a silicon dioxide (SiO ₂ ) film or glass film, 9 and 10 are metal electrodes provided in the base ohmic opening and the emitter opening Thus, a metal such as nickel or aluminum is formed by a technique such as vacuum evaporation.

Generally, when a surge current flows and a surge current passes through the surge protection element, the temperature inside the surge protection element increases. Although the temperature inside the device is local, the allowable melting temperature of silicon (Si) (S
(i. dissolution temperature: 1416 ° C.) or more, and the element is damaged by dissolution of silicon.

[0005]

However, as described above, nickel or aluminum is used as the electrode material of the conventional surge protection element. For example, in the case of aluminum (Al), the silicon melting allowable temperature (1416 ° C.) is used. )
Melting holes are formed in a much lower temperature range (about 580 ° C.), leading to breakage. That is, in the case of the aluminum electrode specification, about 580 ° C., which is the eutectic temperature of Al and Si.
, A reaction occurs between the electrode metals Al and Si, causing damage to silicon such as alois bike at the eutectic temperature level. Therefore, the current is concentrated at the damaged portion, and a sharp rise in temperature occurs at the damaged portion, so that the Si melting point is easily formed or a melting hole is formed, resulting in breakage. This is one of the reasons that conventional products cannot increase the surge resistance.

In view of this point, the present invention uses a refractory metal material having a high eutectic temperature with silicon as the metal in contact with the exposed silicon surface, thereby improving the surge current resistance and A
C is to improve the contact resistance.

[0007]

A two-terminal surge protection element according to a first aspect of the present invention uses a semiconductor substrate of a first conductivity type as a common substrate, and has a base region of a second conductivity type and a first conductivity type on both surfaces thereof. In a two-terminal surge protection element in which an emitter region of a mold type is provided and the exposed surfaces of the base region and the emitter region are short-circuited by metal electrodes, a refractory metal film is formed in contact with the exposed surfaces of the base region and the emitter region. Then, an electrode of a low resistance metal film is formed on the high melting point metal film.

In a two-terminal surge protection device according to a second aspect of the present invention, a first conductive type semiconductor substrate is used as a common substrate, and a second conductive type base region and a first conductive type emitter region are provided on one surface thereof. In a two-terminal surge protection element in which the exposed surfaces of the base region and the emitter region are short-circuited by a metal electrode and the base region and the metal electrode are provided on the other surface of the common substrate, the two-terminal surge protection device is provided on one surface of the common substrate. A refractory metal film is formed in contact with an exposed surface of the base region and the emitter region and an exposed surface of the base region provided on the other surface of the common substrate, and a low-resistance metal film is formed on the refractory metal film. A film electrode is formed.

[0009]

1 shows an embodiment of a two-terminal surge protection device according to the present invention. FIG. 1 (a) is a plan view and FIG.
(B) shows a sectional view. In FIG. 1, 21 is a semiconductor chip, 2 is an N-type or P-type conductive semiconductor substrate, 3
And 4 are P-type or N-type conductive base diffusion portions provided on both surfaces of the semiconductor substrate 2, 5 and 6 are N-type or P-type conductivity emitter diffusion portions provided in the base diffusion portion, and 7 and 8
Is an insulating film formed of a silicon dioxide (SiO ₂ ) film or a glass film, and 11 and 12 are exposed surfaces (ohmic openings) of base diffusion portions 3 and 4 and exposed surfaces (emitter opening portions) of emitter diffusion portions 5 and 6. 2) is a metal film made of a high melting point metal material. The refractory metal film is a metal material having a high eutectic temperature with silicon (Si), such as titanium (Ti), titanium nitride (TiN), tungsten (W), panadium (V), or molybdenum (Mo). Is valid.

Reference numerals 13 and 14 denote metal electrodes provided on the high melting point metal films 11 and 12, respectively, and a metal of a low resistance material such as nickel or aluminum is formed by a method such as vacuum deposition. With such a configuration, the temperature inside the element rises sharply when the surge current is applied. However, the metal electrodes 13 and 14 that come into contact with silicon are made of the above-mentioned high melting point metal material having a high eutectic temperature with silicon. Since it is formed, by increasing the temperature range to the eutectic point, the allowable temperature given to the element can be set high. That is, the surge current allowable value can be increased.

When the electrodes are taken out by wire bonding or connectors, the above-mentioned metal electrodes 13 and 14 of nickel or aluminum are formed by vapor deposition or the like.
It is also possible to directly solder to the high melting point metal films 11 and 12 and to take out. The eutectic temperature of the above-mentioned high melting point metal material titanium (Ti), tungsten (W), panadium (V) or molybdenum (Mo) with silicon (Si) is, as shown in FIG. The temperature is about twice as high as the eutectic temperature of aluminum (Al), so that the surge current withstand capability can be greatly improved.

FIGS. 3A and 3B are a plan view and a sectional view showing a semiconductor chip 31 according to another embodiment of the present invention. In the structure of each part of this embodiment, the same parts as those of the semiconductor chip 21 shown in FIG. 1 are indicated by the same symbols. The semiconductor chip 31 shown in FIG. 3 has the same configuration as that of the semiconductor chip 21 shown in FIG. 1 on the upper side of the semiconductor substrate 2, but does not have an emitter diffusion portion on the base diffusion portion 4 on the lower side. It is said to be a type of surge protection element. Also in this embodiment, the lower side is provided with a high melting point metal film 14 in the base diffusion portion 4 and a metal electrode of a low resistance material such as nickel or aluminum is formed thereon by vacuum deposition or the like. In the case of this embodiment,
As in the case of FIG. 1, by increasing the eutectic temperature, the surge current withstand capability can be greatly improved.

The refractory metal films 13, 1 provided on the exposed surfaces of the base diffusion portions 3, 4 and the emitter diffusion portions 5, 6 are provided.
Reference numeral 4 is formed by vapor deposition, and its film thickness is, for example, about 0.1 μm. This is made thin enough not to impair the eutectic temperature between silicon and the refractory metal film,
This is to prevent the element resistance against the surge current from increasing.

[0014]

As described above in detail, according to the present invention, a metal electrode in contact with silicon is formed of a high melting point metal having a high eutectic temperature with silicon (for example, Ti, TiN, W, V).
Or Mo metal), the temperature range up to the eutectic point can be increased, and the allowable temperature given to the element can be set high.
That is, the surge current allowable value can be increased. Also, when taking out the electrode by wire bond or connector,
This can be dealt with by forming aluminum or nickel into a multilayer metal structure by vapor deposition or the like as the second layer on the high melting point metal.

[Brief description of the drawings]

FIG. 1 is a plan view and a sectional view showing the structure of an embodiment of a two-terminal surge protection device of the present invention.

FIG. 2 is a table showing an example of a eutectic temperature of a combination of a metal and silicon.

FIG. 3 is a plan view and a sectional view showing the structure of another embodiment of the two-terminal surge protection device of the present invention.

FIG. 4 is a plan view and a sectional view showing an example of the structure of a conventional two-terminal surge protection device.

[Explanation of symbols]

 1,21,31 semiconductor chip 2 semiconductor substrate 3,4 base diffusion part 5,6 emitter diffusion part 7,8 insulating film 9,10,13,14 metal electrode 11,12 high melting point metal film

Continued on the front page (72) Inventor Hidetaka Sato 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor Koichi Nishikawa 10-13 Minamicho, Hanno City, Saitama Prefecture Shindengen Kogyo (72) Inventor Hiroaki Iwaguro 10-13 Minamimachi, Hanno City, Saitama Prefecture Shindengen Kogyo Co., Ltd.F-term (reference) 5F005 AA02 AB02 AF01 AH01 AH04 GA01

Claims (6)

[Claims] A semiconductor substrate of a first conductivity type is used as a common substrate, and a base region of a second conductivity type and an emitter region of a first conductivity type are provided on both surfaces thereof, and the exposed surfaces of the base region and the emitter region are formed. In a two-terminal surge protection element short-circuited by a metal electrode, a refractory metal film is formed in contact with the exposed surfaces of the base region and the emitter region, and a low-resistance metal film electrode is formed on the refractory metal film. A two-terminal surge protection element characterized in that: 2. A semiconductor substrate of a first conductivity type is used as a common substrate, a base region of a second conductivity type and an emitter region of a first conductivity type are provided on one surface thereof, and the exposed surfaces of the base region and the emitter region are formed of metal. A two-terminal surge protection element that is short-circuited by an electrode and has a base region and a metal electrode provided on the other surface of the common substrate, wherein the exposed surface of the base region and the emitter region provided on one surface of the common substrate; A high-melting metal film is formed in contact with the exposed surface of the base region provided on the other surface of the common substrate, and a low-resistance metal film electrode is formed on the high-melting metal film. Terminal surge protection element. 3. The two-terminal surge protection device according to claim 1, wherein the first conductivity type is a P-type conductivity type, and the second conductivity type is an N-type conductivity type. 4. The two-terminal surge protection device according to claim 1, wherein the first conductivity type is an N-type conductivity type, and the second conductivity type is a P-type conductivity type. 5. The method according to claim 1, wherein the refractory metal film is made of Ti, TiN,
3. The two-terminal surge protection device according to claim 1, wherein the two-terminal surge protection device is made of W, V, or Mo. 6. The electrode of the low-resistance metal film is made of Al or Ni.
The two-terminal surge protection element according to claim 1 or 2, wherein