JP3131165B2 - Method for manufacturing field electron emission type surge absorbing element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for protecting an electronic circuit of an electronic device from an overvoltage such as a surge that enters through a power line or a communication line, or between lines or between each line and a ground. More particularly, the present invention relates to a method for manufacturing a surge absorbing element using a field electron emission phenomenon.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 8, a surge absorbing element 62 is provided between lines L1 and L2 such as a power supply line and a communication line leading to an electronic circuit 60 of an electronic device, or between each line and GND (ground). To protect the electronic circuit 60 from surges such as induced lightning. That is, when a surge voltage higher than the rating of the surge absorbing element 62 is applied between the lines L1 and L2 or between the lines L1 and L2 and GND, the surge absorbing element 62 conducts and bypasses the surge. This is a mechanism for protecting the electronic circuit 60.

As such a surge absorbing element 62, a gas arrester utilizing a discharge phenomenon in a discharge gap, a varistor which is a high-resistance element having a nonlinear voltage characteristic, or an avalanche (electron avalanche) of a pn junction type semiconductor is used. There are various types such as silicon surge absorbers utilizing the effect, but recently a surge absorbing element using a field electron emission phenomenon has been newly added.

[0004] A surge absorbing element using this field electron emission phenomenon is described in Japanese Patent Application No. 8-132728. As shown in FIGS. 9 and 10, the field emission type surge absorbing element 70 disclosed therein separates a first substrate member 12 and a second substrate member 14 made of an n-type semiconductor at a predetermined distance. And an outer envelope 18 formed by hermetically sealing the periphery of the opposing surface of both members via a frame member 16 also serving as a spacer. 10 ^-6 ~
It is maintained at a high vacuum of 10 ^-8 Torr.

On the opposite surface of the first substrate member 12, a number of emitter cones 20 made of an n-type semiconductor are provided.
The projections are provided at predetermined intervals. The emitter cone 20 has a pointed cone or pyramid shape,
The front end faces the facing surface of the second substrate member 14.

The first including the surface of the emitter cone 20
The Nb, W, Mo, Cr, Ti, Th, Si, Ni,
A thin film made of La, Ge, Al or the like, a two-layer structure of W and Zr, or a protective film 22 made of carbide, oxide, nitride, or inorganic compound containing at least one of the above substances Is coated.

On the outer surface of the first substrate member 12, a first external electrode layer 24 having a two-layer structure of a first layer 24a and a second layer 24b is formed. The cathode terminal 28 is connected to the external electrode layer 24. A second external electrode layer 26 having a two-layer structure of a first layer 26a and a second layer 26b is also formed on the outer surface of the second substrate member 14,
The anode terminal 30 is connected to the second external electrode layer 26. Then, connect each terminal 28, 30 to the line L1, L2 or G
By connecting to the ND, the field electron emission type surge absorbing element 70 is inserted and connected between the lines L1, L2 or between the lines L1, L2 and GND, as shown in FIG.

The line L1 and L2 or the line L
1. When an overvoltage exceeding a rating such as a surge is applied between L2 and GND, and strong electric field concentration occurs at the tip 20a of the emitter cone on the cathode side, electrons in the n-type semiconductor are caused by a quantum mechanical tunnel effect. A so-called field electron emission phenomenon that is emitted into a vacuum beyond the potential barrier occurs. The emitted electrons are captured on the anode side of the high potential, that is, on the facing surface of the second substrate member 14, so that a precursor discharge in which a current flows between the second substrate member 14 and the first substrate member 12 is generated. This precursor discharge then shifts to vacuum spark discharge (vacuum arc discharge).

The following is conceivable as a mechanism in which the precursor discharge shifts to a vacuum spark discharge. That is, due to the action of thermal energy generated by the increase in current density at the tip end portion 20a of the emitter cone due to electron emission during the precursor discharge, the metal constituting the protective film 22 covering the surface of the emitter cone 20 is changed from metal to metal. A protective film covering the opposing surface of the second substrate member 14 due to thermal energy generated as a result of generation of steam or collision of electrons due to the precursor discharge with the anode side.
Similarly, metal vapor is generated from the 22 metals, and these charged metal vapors serve as elements for forming an electric current to generate a vacuum spark discharge. Further, it is practically difficult to make the inside of the envelope 18 a complete vacuum, and gas molecules are slightly adsorbed or adhered to the surface of the material constituting the discharge space. Is released into the space by the impact of the precursor discharge, and the ionized gas molecules serve as elements for forming a current. This is also a factor promoting vacuum spark discharge.

The above-mentioned field electron emission phenomenon occurs only when the electric field intensity concentrated on the emitter cone 20 becomes higher than a predetermined value. This occurs when a voltage higher than a predetermined value is applied between both electrodes. Only means that a current flows between both electrodes. In other words, since a nonlinear relationship appears between the value of the voltage applied between the two electrodes and the flowing current, surge absorption occurs only when an overvoltage exceeding the rated voltage is applied and the overvoltage is bypassed. The function can be exerted.

Furthermore, compared to the speed of electrons in a semiconductor, electrons in a vacuum travel without being scattered, so that the field electron emission type surge absorbing element 70 can operate at an extremely high speed. Further, since the semiconductor device does not have a junction structure between the p-type semiconductor and the n-type semiconductor, there is no problem that the capacitance is increased unlike the silicon surge absorber.

FIG. 11 shows the surge absorption characteristics of such a field emission type surge absorbing element 70.
It is a graph which shows the surge absorption waveform with respect to the original surge waveform whose peak voltage value is 3 kV. As shown in the figure, when a surge voltage is applied, a precursor discharge having a peak of about 2.32 kV is instantaneously generated.
A state in which a stable surge absorption waveform of 0 V is obtained is shown.

FIG. 12 shows another example of a field electron emission type surge absorbing element. In this field electron emission type surge absorbing element 72, a first substrate member 12 and a second substrate member 14 made of an n-type semiconductor are arranged to face each other at a predetermined distance,
The above-mentioned point is that the envelope 18 is formed by hermetically sealing the peripheral edges of the facing surfaces of both members with the frame member 16 interposed therebetween, and the internal space of the envelope 18 is in a high vacuum state. It is common to the field electron emission type surge absorbing element 70.

On the other hand, the opposing surface of the first substrate member 12 has a first electron-emitting portion 34 having a large number of emitter cones 20 projecting therefrom, and a planar shape without the emitter cone 20 being formed. The second substrate member 14 is divided into a plurality of first flat portions 35 which are maintained, and a plurality of emitters
It is characterized in that it is divided into a second electron emitting portion 36 in which the cone 20 is protruded, and a second flat portion 37 in which an emitter cone is not formed and maintains a flat shape. I have. Then, the first electron emission portion 34 of the first substrate member 12 is opposed to the second plane portion 37 of the second substrate member 14, and the second electron emission portion of the second substrate member 14 is 36 is the first substrate member
The two substrate members are positioned so as to face the first flat portion 35 of the substrate 12.

On the opposing surfaces of the two substrate members, the same protective films 22 as described above are formed. A first external electrode layer 24 is formed on the outer surface of the first substrate member 12, and a first external terminal 38 is connected to the first external electrode layer 24. Further, a second external electrode layer 26 is formed on the outer surface of the second substrate member 14, and a second external terminal 40 is connected to the second external electrode layer 26.

The field electron emission type surge absorbing element 72
By providing the emitter cone 20 on the first external terminal 38 side and the second external terminal 40 side as described above,
It has a structure capable of bidirectionally emitting electrons between the first external electrode layer 24 and the second external electrode layer 26, and can be used without concern for polarity. This has an advantage that it can cope with the case where the voltage is applied.

In the case of a field electron emission type surge absorbing element, it is necessary to maintain the inside of the envelope 18 in a high vacuum state. To this end, one of the first substrate member 12 and one of the frame members 16 is required. Joining between end faces, and second substrate member 14 and frame member 16
Is required to be realized while maintaining a sufficiently high airtightness.

The first substrate member 12 and the second substrate member 14 are joined to the frame member 16 by fusing using frit glass or low-melting glass, or using a polyimide-based organic adhesive. The method of bonding is generally used, but in both cases, unnecessary gas is generated in the bonding step, so it is necessary to exhaust the gas inside the envelope 18 after bonding. In order to perform this degassing process, an exhaust pipe must be connected to the envelope 18, and even if the exhaust pipe is melted and sealed and cut off after evacuation, the melt-sealed portion protrudes. Since it is left as it is, it is inevitable that the thickness of the entire envelope 18 increases. In addition, particularly in the case of a bonding method using an organic adhesive, not only gas is gradually released during the use process, but also a problem that the bonding strength is reduced when used in a relatively high temperature environment. It had been. Then, in order to overcome the shortcomings of these bonding methods, the use of the anodic bonding method has recently been increasing.

A process for forming the envelope 18 using the anodic bonding method will be described with reference to FIGS. First, as shown in FIG. 13, the second substrate member 14 is placed on the hot plate 42 with the second external electrode layer 26 facing down, and mobile ions such as Na ⁺ and H ⁺ are placed inside. One end surface of the frame member 16 made of glass is included on the peripheral edge 14a of the facing surface of the second substrate member 14. On the other end surface of the frame member 16, an electrode plate having a shape corresponding to the end surface shape of the frame member 16 is provided.
74 is crimped. The positive side of the DC power supply 46 is connected to the second external electrode layer 26 of the second substrate member 14 via the hot plate 42, and the negative side of the DC power supply 46 is connected to the electrode plate 74. Connected. Then, the second substrate member 14 and the frame member are
16 is heated to 200 to 600 degrees Celsius, and a DC voltage of 50 to 1000 V is applied from the DC power supply.

As a result, as shown in FIG. 14, after a certain period of time, the cations 48 in the frame member 16 move to the minus side (ie, near the upper end surface of the frame member 16), and the second substrate member 14 The negative charge is concentrated near the periphery 14a of the opposed surface to form the space charge layer 50, and a chemical bond accompanied by a large attractive force is generated, thereby realizing anodic bonding.

After the solid bonding between the peripheral edge 14a of the second substrate member and one contact surface of the frame member 16 has been completed as described above, as shown in FIG. Inside, the first substrate member 12 is placed on the hot plate 42 with the first external electrode layer 24 facing down, and the frame member 16
Is brought into contact with the peripheral edge 12a of the opposing surface of the first substrate member. The positive side of the DC power supply 46 is connected to the first external electrode layer 24 of the first substrate member 12 via the hot plate 42, and the second external electrode layer 24 of the second substrate member 14 The negative side of the DC power supply 46 is connected to 26.
Then, while the first substrate member 12 and the frame member 16 are heated to 200 to 600 degrees Celsius by the hot plate 42, a DC voltage of 50 to 1000 V is applied from the DC power supply 46. As a result, a strong anodic bonding between the peripheral edge 12a of the first substrate member and the contact surface of the frame member 16 is realized by the same mechanism as described above, and the envelope 18 having high airtightness is completed. You do it.

[0022]

The above-described anodic bonding method comprises:
Since no molten glass or adhesive is used, both the substrate member and the frame member can be joined with high positional accuracy,
It has the advantage that degassing after joining is unnecessary. However, the conventional manufacturing method of joining the two substrate members and the frame member using the anodic bonding method has the following disadvantages.

First, since the joining between the second substrate member 14 and the frame member 16 and the joining between the first substrate member 12 and the frame member 16 are performed separately, there is a problem that the manufacturing efficiency is low. . Next, the thickness of the frame member 16 is thin (for example, 500 μm
In the following case, when the second substrate member 14 and the frame member 16 are joined (FIG. 13), the cations 48 in the frame member 16 are excessively accumulated near the end face on the electrode plate 74 side, and as a result, the frame member 16 And the end face is brought into contact with the peripheral edge 12a of the opposing surface of the first substrate member 12 (FIG. 15). Even if a negative potential is applied to the second substrate member 14 side, as shown in FIG. 48 cannot move to the second substrate member 14 side. For this reason, a space charge layer cannot be formed in the vicinity of the contact surface with the first substrate member 12, and it may be difficult to perform anodic bonding between the first substrate member 12 and the frame member 16. Further, in the case of the field electron emission type surge absorbing element 72 capable of discharging in both directions shown in FIG.
As shown in FIG. 7, when the frame member 16 and the first substrate member 12 are joined together, the emitter cone 20 on the second substrate member 14 side is used.
, A voltage is applied in a direction in which field electron emission is caused. Therefore, when the applied voltage is equal to or higher than the rated voltage of the surge absorbing element 72,
Electrons are emitted from the tip 20a of the emitter cone of the second substrate member 14 to start a surge absorbing operation, and the first substrate member 12 and the second substrate member 14 are electrically connected in the envelope 18 to be conducted. For this reason, a space charge layer cannot be formed in the frame member 16, and anodic bonding between the frame member 16 and the first substrate member 12 becomes impossible. For this reason, the anodic bonding method cannot be applied to devices other than devices having a rated voltage higher than the voltage value applied in the bonding step.

The present invention has been devised in order to solve the drawbacks of the conventional anodic bonding method, and its object is to bond the second substrate member to the frame member, and to achieve the first and second methods. The joining of the substrate member and the frame member can be achieved at the same time, and even when the thickness of the frame member is set to be relatively small, the joining does not become impossible, and the first substrate member and the second Even in the case of a field electron emission type surge absorption element of a type capable of emitting electrons in both directions of the substrate member,
An object of the present invention is to realize a joining method that does not cause a surge absorbing operation due to voltage application in a joining process.

[0025]

In order to achieve the above object, a method of manufacturing a surge absorbing element according to the present invention comprises an electron emitting portion made of a semiconductor and having a plurality of emitter cones integrally formed on one surface. A first substrate member having an external electrode layer formed on the other surface, and a second substrate formed of a semiconductor and having a flat portion on one surface and an external electrode layer formed on the other surface. Are arranged such that the tip of the emitter cone of the first substrate member and the plane portion of the second substrate member face each other at a predetermined distance, and the two substrates are placed in a vacuum atmosphere. In a method of manufacturing a field electron emission type surge absorbing element in which an outer peripheral surface of a member is hermetically sealed with a frame member interposed therebetween to form an envelope whose inside is in a high vacuum state, With mobile ions inside Consists of an insulating material including, a first contact surface in contact with the facing surface peripheral edge of the first substrate member,
The first substrate member is provided with a second contact surface in contact with a peripheral edge of the opposing surface of the second substrate member, and an outer peripheral portion protruding from the outer surfaces of both the substrate members disposed opposite to each other. , A frame member, and a second substrate member are sequentially stacked and mounted, and a metal band is formed on the outer peripheral edge end surface of the frame member so as to be bent into a shape corresponding to the outer peripheral edge end surface and covers the outer peripheral edge end surface. The electrode frame composed of the above-mentioned electrodes is press-bonded, and the external electrode layers of both the substrate members are connected to the positive side of the DC power supply, respectively, and the electrode frame is connected to the negative side of the DC power supply, and heated to a predetermined temperature. In a vacuum atmosphere, by applying a voltage from the DC power source, a voltage is uniformly applied to the entire end face of the outer peripheral edge of the frame member. At the same time as anodically bonding the first contact surface of the frame member to the first contact surface, An abutment surface second opposing surface perimeter and the frame member of the board members, characterized in that anodic bonding.

In another method of manufacturing a field emission type surge absorbing element according to the present invention, an electron emission portion having a plurality of emitter cones integrally formed on one surface and an emitter cone are not formed. A first substrate member having a flat portion and an external electrode layer formed on the other surface; an electron emission portion formed of the same semiconductor and having a large number of emitter cones integrally formed on one surface; A second substrate member having an external electrode layer formed on the other surface, comprising: a front end portion of the emitter cone of one substrate member; and a flat portion of the other substrate member. Are arranged so as to face each other with a predetermined distance therebetween, and the inside is made to be in a high vacuum state by hermetically sealing the peripheral edges of the opposing surfaces of both substrate members in a vacuum atmosphere with a frame member interposed therebetween. The method of manufacturing a field electron emission type surge absorber forming the envelope, as the frame member,
It is composed of an insulating material containing movable ions inside,
A first contact surface in contact with the peripheral edge of the opposing surface of the substrate member, a second contact surface in contact with the peripheral edge of the opposing surface of the second substrate member,
The first substrate member, the frame member, and the second substrate member are sequentially stacked and mounted, and the frame member is provided with an outer peripheral portion protruding from the outer surface of both of the opposed substrate members. An electrode frame made of a metal band which is bent into a shape corresponding to the outer peripheral edge end face and is crimped to the outer peripheral edge end face, and a DC power supply is applied to the external electrode layers of both substrate members. By connecting the negative side of the DC power supply to the electrode frame, and applying a voltage from the DC power supply in a vacuum atmosphere heated to a predetermined temperature, thereby forming the frame member. A voltage is applied uniformly to the entire end surface of the outer peripheral edge of the first substrate member, whereby the peripheral edge of the opposing surface of the first substrate member and the first contact surface of the frame member are anodically bonded, and at the same time, the second substrate The periphery of the opposing surface of the member and the second contact surface of the frame member Characterized by polar bonding.

The frame member is made of, for example, borosilicate glass containing Na ⁺ inside.

When a predetermined voltage was applied from the DC power supply to join the first substrate member and the second substrate member to the frame member, the negative side of the DC power supply was connected via the electrode frame. Positive ions are accumulated at the outer peripheral edge of the frame member, while the interface portion between the first substrate member and the second substrate member connected to the positive side of the DC power source (that is, the first portion of the frame member). Negative charges accumulate on the contact surface and the second contact surface) to generate a space charge layer, and anodic bonding of the first and second substrate members and the frame member is simultaneously realized. You. That is, since the joining between the other substrate member and the other end surface of the frame member is not started after the joining of the one substrate member and the one end surface of the frame member is completed as in the related art, Positive charges excessively accumulated in the vicinity of one end face cannot be moved to the other end face side at the time of joining with the other substrate member, so that the problem that anodic joining itself becomes difficult does not occur from the beginning. .
Of course, the joining between the first substrate member and the frame member, and the second
Since the bonding of the substrate member and the frame member can be realized at the same time, improvement in manufacturing efficiency can also be achieved. In addition, an electrode frame made of a metal band that is bent into a shape corresponding to the outer peripheral edge end face and is pressed on the outer peripheral edge end face of the frame member, and the direct current is applied to the electrode frame. By connecting the negative side of the power supply, a voltage is uniformly applied to the entire end face of the outer peripheral edge, so that the cations in the frame member are uniformly accumulated near the end face of the outer peripheral section, and the first of the frame member is The space charge layer is formed evenly on the contact surface and the second contact surface. For this reason, the joining of the peripheral edge of the facing surface of the first substrate member to the first contact surface of the frame member and the joining of the peripheral edge of the facing surface of the second substrate member to the second contact surface of the frame member are performed. It can be very strong. As the frame member, a first substrate member and a second substrate member
The reason for adopting the one with the outer peripheral edge protruding from the outer surface of the substrate member is to secure a space for storing a positive charge when a voltage is applied by connecting the negative side of the DC power supply. is there. Further, the outer peripheral edge of the frame member is the first edge.
Projecting from the outer surface of the substrate member and the second substrate member
Therefore, the external electrode layer of the first substrate member and the external electrode layer of the second substrate member
The creepage distance between the external electrode layers should be
Used as surge absorbing element
During the discharge, instead of being generated inside the envelope,
Conduction between the external electrode layers through the outer surface of the envelope
Can be effectively prevented.

Also, at the time of bonding, the first substrate member and the second
Since the same potential voltage is simultaneously applied to the first and second substrate members, even a field-emission-type surge absorbing element of a type in which an emitter cone is formed on both the first and second substrate members. In addition, no discharge occurs in the envelope regardless of the applied voltage value. Therefore, even if the value of the voltage applied at the time of joining is equal to or higher than the operating voltage of the field emission type surge absorbing element, surge absorbing operation does not occur, and anodic joining can be realized effectively.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, in a first field emission type surge absorbing element 10 according to the present invention, a first substrate member 12 and a second substrate member 14 are separated by a predetermined distance. The peripheral edge 12a of the opposing surface of the first substrate member and the peripheral edge 14a of the opposing surface of the second substrate member are separated from each other by the first contact surface 16 of the frame member 16.
a and the second contact surface 16b are hermetically bonded to each other to form an envelope 18, and the interior of the envelope 18 is maintained in a high vacuum state of 10 ^-6 to 10 ^-8 Torr. As shown in FIG. 2, the frame member 16 has a shape in which a middle portion of a rectangular glass plate is largely cut out in a rectangular shape. Since the vertical dimension and the horizontal dimension of the frame member 16 are set to be larger than the vertical dimension and the horizontal dimension of the first substrate member 12 and the second substrate member 14, the peripheral edge of the opposing surface of the first substrate member is set. The notch of the frame member 16 is formed by the peripheral edge 14a of the facing surface 12a and the second substrate member.
When each board member is joined so as to just block 17, the frame member 16
Of the first substrate member 12 and the second substrate member 14
(FIG. 1).

On the opposing surface of the first substrate member 12, a large number of emitter cones 20 are provided projecting over substantially the entire surface at predetermined intervals. Although FIG. 1 is a cross-sectional view, only one row of emitter cones 20 is shown. However, in practice, the emitter cones 20 are arranged vertically and horizontally at regular intervals (FIG. 2). The first substrate member 12 is formed of an n-type semiconductor obtained by mixing impurities such as P and As into Si. The emitter cone 20 is also made of an n-type semiconductor and is formed integrally with the first substrate member 12.
The emitter cone 20 has a pointed cone or pyramid shape, and the tip 20 a faces the facing surface of the second substrate member 14. However, a predetermined gap is maintained between the tip 20a of the emitter cone 20 and the opposing surface of the second substrate member 14. The height of the emitter cone 20 is set to about 5 μm, the diameter of the bottom is set to about 3 to 10 μm, the pitch between the emitter cones 20 is set to about 7.5 to 15 μm, and the angle of the tip is set to 25 to 30 degrees. Have been.

The first including the surface of the emitter cone 20
The facing surface of the substrate member 12 is coated with a protective film 22. This protective film 22 is made of Nb, W, Mo, Cr, Ti, T
h, Si, Ni, La, Ge, Al, diamond (amorphous carbon) and other thin films, W and Zr
Two-layer structure, or at least one of the above substances
It is composed of carbides, oxides, nitrides, and inorganic compounds containing various types. On the outer surface of the first substrate member 12, a first layer 24a formed by evaporating Al or Cr and a second layer 24b formed by evaporating Ni on the surface of the first layer 24a are formed. A first external electrode layer 24 is formed. This first
Al or Cr forming the second layer 24b and Ni forming the second layer 24b have good ohmic contact (ohmic contact).
t).

The second substrate member 14 is made of an n-type semiconductor similarly to the first substrate member 12, and has a facing surface covering the surface of the emitter cone 20 and the like. A protective film 22 made of a similar material is formed. Further, on the outer surface of the second substrate member 14, a first layer 26a formed by evaporating Al or Cr, and a second layer 26b formed by evaporating Ni on the surface of the first layer 26a. The second consisting of
The external electrode layer 26 is formed.

As is clear from the above, in the first field electron emission type surge absorbing element 10, the entire area of the opposing surface of the first substrate member 12 constitutes an electron emission portion.
The entire opposing surface of the second substrate member 14 constitutes a plane portion. In addition, as the constituent material of the second substrate member 14, other than the n-type semiconductor, other substances having substantially the same thermal expansion coefficient as the first substrate member 12 can be used. For example, Mo corresponds to this. I do.

The first external electrode layer 24 and the second external electrode layer 26 do not necessarily have to have a two-layer structure, and may be formed by evaporating only Ni. As a material of the frame member 16, borosilicate glass (trade name: Pyrex glass) having a thermal expansion coefficient close to that of an n-type semiconductor and containing Na ⁺ as mobile ions is used.

The first external electrode layer 24 has a cathode terminal
28, and an anode terminal 30 is connected to the second external electrode layer 26 (FIG. 1). Then, by connecting each terminal to the line L1, L2 or GND in the same manner as shown in FIG.
1 and L2 or between lines L1 and L2 and GND. When a surge voltage exceeding the rated voltage is applied between the lines L1 and L2 or between the lines L1 and L2 and GND, a strong electric field concentration occurs at the tip 20a of the emitter cone 20, and a quantum mechanical tunnel effect occurs. As a result, electrons pass through a potential barrier on the surface and are emitted into a vacuum. Electrons generated by this so-called field electron emission phenomenon are captured on the opposing surface of the second substrate member 14, so that a precursor discharge in which a current flows between the second substrate member 14 and the first substrate member 12 is generated. By absorbing the precursor discharge into a vacuum spark discharge, the surge can be absorbed.

For convenience of illustration, the size of the emitter cone 20 is illustrated with emphasis in FIGS. 1 and 2;
In contrast to the unit size, the first substrate member 12 has a size of mm unit (for example, 2 to 6 mm square), and tens to hundreds of thousands of emitter cones 20 are formed. By the way,
The overall size of the first field emission type surge absorbing element 10 is about 6 mm square and about 0.6 mm thick.

FIG. 3 shows a second field emission type surge absorbing element 32 according to the present invention. In this second field emission type surge absorbing element 32, a first substrate member 12 and a second substrate member 14 made of an n-type semiconductor are arranged to face each other at a predetermined distance from each other. Is sealed in a hermetic manner with a frame member 16 interposed therebetween to form an envelope 18, and the internal space of the envelope 18 is in a high vacuum state of 10 ^-6 to 10 ^-8 Torr. And the first field-emission type surge absorbing element 10 described above. Also, the outer peripheral edge 19 of the frame member 16
However, they are also common in that they protrude from the outer side surfaces of the first substrate member 12 and the second substrate member 14.

On the other hand, the opposing surface of the first substrate member 12 is in contact with a first electron-emitting portion 34 in which a large number of emitter cones 20 are arranged in a dot matrix at predetermined intervals. , And a first flat portion 35 which maintains a flat shape without forming the emitter cone 20. Further, the opposing surface of the second substrate member 14 also includes a second electron-emitting portion 36 in which a large number of emitter cones 20 are arranged in a dot matrix at a predetermined distance, and an emitter cone.
The second flat portion 37 in which the flat shape is maintained without forming the 20
It is divided into and. As shown, the first substrate member 12
The first electron-emitting portion 34 of the second substrate member 14 faces the second plane portion 37 of the second substrate member 14, and the second electron-emitting portion 36 of the second substrate member 14 The two substrate members are positioned so as to face the first flat portion 35 of the first substrate. Then, the tip portion 20a of the emitter cone 20 and the flat portions 35, 37
A predetermined gap is maintained between the two.

The opposing surfaces of the two substrate members (the first electron-emitting portion 3
4, the second electron-emitting portion 36, the first flat portion 35, and the second flat portion 37) are each provided with a protective film 22 made of the same substance as described above. A first external electrode layer 24 having a two-layer structure of a first layer 24a made of Al or Cr and a second layer 24b made of Ni is formed on the outer surface of the first substrate member 12. The first external electrode layer 24 has the first
External terminals 38 are connected. Further, a first layer 26a made of Al or Cr is formed on the outer surface of the second substrate member 14.
And a second layer 26b made of Ni and Ni.
Is formed, and the second external electrode layer
26 is connected to a second external terminal 40.

This second field electron emission type surge absorbing element
32, the emitter cone 20 is provided on the first substrate member 12 side and the second substrate member 14 side as described above, so that the first external electrode layer 24 and the second external electrode layer 26 It has the advantage of being able to emit electrons in both directions between the electrodes, and has the advantage that it can be used without concern for polarity and that it can cope with the case where an overvoltage is applied in the reverse direction for some reason. .

Next, a method of joining the first substrate member 12, the second substrate member 14, and the frame member 16 in the first field emission type surge absorbing element 10 will be described. First, in a vacuum atmosphere, as shown in FIG. 4, the first substrate member 12 on which the emitter cone 20 and the first external electrode layer 24 have been formed,
And the second substrate member 14 on which the second external electrode layer 26 has been formed.
And are stacked.

An electrode frame 44 is crimped to the outer peripheral edge end surface 19a of the frame member 16. As shown in FIG. 5, the electrode frame 44 is formed by bending a flexible conductive metal band into a rectangular shape so as to correspond to the outer peripheral edge 19 of the frame member 16. I have. After opening and closing the open / close end 44a of the electrode frame 44 in the left-right direction and guiding the outer peripheral edge 19 of the frame member 16 into the electrode frame 44, and closing the open / close end 44a, the electrode frame 44 itself has By the restoring force, the outer peripheral edge end surface 19a of the frame member 16 and the inner surface of the electrode frame 44 are pressed. And FIG.
As shown in FIG. 3, the second external electrode layer 26 of the second substrate member 14 is formed.
Is connected to the positive side of the DC power supply 46, and the hot plate is also connected to the first external electrode layer 24 of the first substrate member 12.
The positive side of the DC power supply 46 is connected via 42. Further, the electrode frame 44 covering the outer peripheral edge end surface 19a of the frame member 16 includes:
The negative side of DC power supply 46 is connected.

Thus, 50 to 10 from the DC power supply 46
When a voltage of 00 V is applied, as shown in FIG. 6, the cations (Na ⁺ ) 48 inside the glass constituting the frame member 16 move to the electrode frame 44 side, and at the same time, the first substrate member 12 and the The space charge layer 50 is formed in the vicinity of the interface with the second substrate member 14 by concentrating the negative charges, and a large attractive force is generated, so that the first substrate member 12 and the second substrate member 14 Chemically bonded. That is, the peripheral edge 12a of the opposing surface of the first substrate member
Anodic bonding between the first contact surface 16a of the frame member 16 and the second
Peripheral edge 14a of the opposing surface of the substrate member and the second contact surface of the frame member 16
The anodic bonding with 16b is realized at the same time.

As described above, the outer peripheral portion 19 of the frame member 16 is configured to protrude from the outer surfaces of the first substrate member 12 and the second substrate member 14 because of the movement of the cations 48. This is for securing the storage destination, and as a result, the following effects occur. That is, the creepage distance between the first external electrode layer 24 of the first substrate member 12 and the second external electrode layer 26 of the second substrate member 14 is longer than that of the outer peripheral edge 19 made of an insulating material. Therefore, during use as a surge absorbing element, instead of generating discharge inside the envelope 18, the envelope 18
The conduction between the two external electrode layers through the outer surface of the substrate can be effectively prevented.

The reason why the electrode frame 44 is crimped so as to surround the outer peripheral edge 19 of the frame member 16 is to apply an electric field uniformly to the entire end face 19a of the outer peripheral edge. In addition,
In order to make the above anodic bonding more robust,
It is necessary to smooth as much as possible the peripheral edge 12a of the opposing surface of the substrate member, the peripheral edge 14a of the opposing surface of the second substrate member, and the contact surfaces 16a and 16b of the frame member 16 as much as possible. Is desirably suppressed to 1 μm or less.

The bonding between the first substrate member 12, the second substrate member 14, and the frame member 16 in the second field emission type surge absorbing element 32 is performed in the same manner as described above. That is, as shown in FIG. 7, in a vacuum atmosphere, the first substrate member 12 on which the emitter cone 20 and the first external electrode layer 24 have been formed, And the second substrate member 14 on which the second external electrode layer 26 has been formed is stacked and mounted with the frame member 16 interposed therebetween, and the first external electrode layer 24 and the second external electrode layer 26 Are connected to the positive side of the DC power supply 46, and are connected to the electrode frame 44 which is crimped to the outer peripheral edge 19a of the frame member 16.
Is connected to the negative side of the DC power supply 46.

When a predetermined DC voltage is applied from the DC power supply 46 while heating to 200 to 600 degrees Celsius using the hot plate 42, the frame member 16 is omitted from the drawing.
The cations (Na ⁺ ) inside move to the contact surface side with the electrode frame 44, and a space charge layer is formed near the interface between the first substrate member 12 and the second substrate member 14, and the frame member 16 Anodic bonding between the contact surface of the substrate member and the peripheral edge of the opposing surface of each substrate member is realized. At the time of joining the second field emission type surge absorbing element 32, the same electric potential is applied to both the emitter cone 20 on the first substrate member 12 and the emitter cone 20 on the second substrate member 14 at the same time. , No discharge is generated between the two substrate members. Therefore, the value of the voltage applied in the bonding step is the second field emission type surge absorbing element.
Even at a rated voltage of 32 or more, anodic bonding can be performed effectively.

In the above description, an example is shown in which an n-type semiconductor is used as the material of the first substrate member 12 and the second substrate member 14, but the present invention is not limited to this.
It is also applicable when the first substrate member 12 and the second substrate member 14 formed of a p-type semiconductor in which an impurity such as boron is mixed in i are anodically bonded through a frame member 16 therebetween. It is.

[0050]

According to the method of manufacturing a field emission type surge absorbing element according to the present invention, the joining of the first substrate member and the second substrate member can be realized at the same time. Not only can be achieved, but also in the case where the thickness of the frame member is configured to be relatively thin, the joining between the peripheral edge of the opposing surface of the first substrate member and the first contact surface of the frame member, and The joining between the peripheral edge of the opposing surface of the second substrate member and the second contact surface of the frame member can be reliably performed. Also, by crimping an electrode frame made of a metal band bent into a shape corresponding to the outer edge portion end surface on the outer edge portion end surface of the frame member, and connecting the minus side of the DC power supply to the electrode frame. In order to apply a voltage uniformly to the entire end surface of the outer peripheral portion, the cations in the frame member are uniformly accumulated near the end surface of the outer peripheral portion, and the first contact surface and the second contact surface of the frame member. The space charge layer is formed evenly on the surface. For this reason, the joining of the peripheral edge of the facing surface of the first substrate member to the first contact surface of the frame member and the joining of the peripheral edge of the facing surface of the second substrate member to the second contact surface of the frame member are performed. It can be very strong. Further, the first substrate member and the second
Since the same potential voltage is applied to the substrate members at the same time, even if the field electron emission type surge absorbing element has an emitter cone formed on both the first substrate member and the second substrate member. In addition, anodic bonding can be reliably realized without generating a discharge in the envelope due to voltage application at the time of bonding.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first field emission type surge absorbing element according to the present invention.

FIG. 2 is an exploded perspective view showing a first field electron emission type surge absorbing element.

FIG. 3 is a sectional view showing a second field-emission-type surge absorbing element according to the present invention.

FIG. 4 is a schematic cross-sectional view showing a joining step of a first substrate member, a frame member, and a second substrate member in the first field emission type surge absorbing element.

FIG. 5 is a perspective view showing an electrode frame.

FIG. 6 is a conceptual diagram showing a principle of joining a first substrate member, a frame member, and a second substrate member.

FIG. 7 is a schematic cross-sectional view showing a joining step of a first substrate member, a frame member, and a second substrate member in the second field-emission surge absorbing element.

FIG. 8 is a circuit diagram showing a usage example of a surge absorbing element.

FIG. 9 is a cross-sectional view showing a conventional field emission type surge absorbing element.

FIG. 10 is an exploded perspective view showing a conventional field emission type surge absorbing element.

FIG. 11 is a waveform chart showing surge absorption characteristics of a field emission type surge absorption element.

FIG. 12 is a cross-sectional view showing another example of a conventional field emission surge absorbing element.

FIG. 13 is a schematic cross-sectional view showing a step of joining a second substrate member and a frame member in a conventional field emission surge absorbing element.

FIG. 14 is a conceptual diagram illustrating the principle of the anodic bonding method.

FIG. 15 is a schematic cross-sectional view showing a step of joining a first substrate member and a frame member in a conventional field emission surge absorbing element.

FIG. 16 is a conceptual diagram illustrating a problem of a conventional anodic bonding method.

FIG. 17 is a schematic cross-sectional view showing a step of joining a first substrate member and a frame member in a conventional field emission type surge absorbing element.

[Explanation of symbols]

 10 First field electron emission type surge absorbing element 12 First substrate member 12a Peripheral edge of first substrate member facing opposite side 14 Second substrate member 14a Peripheral edge of second substrate member facing surface 16 Frame member 16a Frame member 16a First contact surface 16b Second contact surface of frame member 19 Outer peripheral edge of frame member 19a End surface of peripheral edge of frame member 18 Envelope 20 Emitter cone 24 First external electrode layer 26 Second External electrode layer 32 Second field-emission type surge absorbing element 34 First electron-emitting section 35 First plane section 36 Second electron-emitting section 37 Second plane section 44 Electrode frame 46 DC power supply 48 Cation

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01T 1/00-4/20

Claims (3)

(57) [Claims] 1. A semiconductor device comprising: a first substrate member having an electron emission portion formed integrally with a plurality of emitter cones on one surface and having an external electrode layer formed on the other surface; A second substrate member having a plane portion on one surface and an external electrode layer formed on the other surface, and a tip portion of the emitter cone of the first substrate member and the second substrate member. It is arranged so that the flat part of the substrate member faces a predetermined distance, and the periphery of the facing surface of both substrate members is hermetically sealed with a frame member therebetween in a vacuum atmosphere, so that the inside of the substrate member has a high vacuum. In the method for manufacturing a field electron emission type surge absorbing element forming an envelope in a state, the frame member is formed of an insulating material containing movable ions therein, and is provided with a peripheral edge of a facing surface of the first substrate member. A first abutting surface in contact with the The first substrate member is provided with a second contact surface that is in contact with the peripheral edge of the opposing surface of the second substrate member, and an outer peripheral portion that protrudes from the outer surfaces of both the substrate members that are disposed opposite to each other. the frame member, the stacked mounting the second substrate member in order, the outer peripheral edge end face of the frame member is bent into a shape corresponding to the outer peripheral end face, the outer periphery end surface
An electrode frame made of a metal band to be covered is crimped, and a positive side of a DC power supply is connected to the external electrode layers of the both substrate members, respectively, and a negative side of the DC power supply is connected to the electrode frame at a predetermined temperature. In a vacuum atmosphere heated to
By applying a voltage from the DC power supply, a voltage is uniformly applied to the entire end surface of the outer peripheral edge of the frame member,
At the same time, the peripheral edge of the facing surface of the first substrate member and the first contact surface of the frame member are anodically bonded, and the peripheral edge of the facing surface of the second substrate member and the second contact surface of the frame member are simultaneously joined. A method for manufacturing a field electron emission type surge absorbing element, comprising anodic bonding. 2. An electronic device comprising: a semiconductor; an electron emission portion having a plurality of emitter cones integrally formed on one surface; and a flat portion having no emitter cone formed on one surface, and an external electrode layer formed on the other surface. A first substrate member, which is also made of a semiconductor, has an electron emission portion integrally formed with a large number of emitter cones on one surface, and a flat portion on which no emitter cone is formed, and has an external electrode layer formed on the other surface. And a second substrate member is formed such that the tip of the emitter cone of one substrate member and the plane portion of the other substrate member face each other at a predetermined distance, and are placed in a vacuum atmosphere. In the method for manufacturing a field electron emission type surge absorbing element forming an envelope in which a high vacuum state is formed by hermetically sealing the peripheral edges of the opposing surfaces of both substrate members with a frame member therebetween, The frame member is made of an insulating material containing movable ions therein, and has a first contact surface in contact with the peripheral edge of the opposing surface of the first substrate member, and a second contact surface in contact with the peripheral edge of the opposing surface of the second substrate member. 2, the first substrate member, the frame member, and the second substrate member are sequentially stacked and mounted. While being placed, the outer peripheral edge of the frame member is bent into a shape corresponding to the outer peripheral edge ,
An electrode frame made of a metal band covering the outer peripheral end face is crimped, and a positive side of the DC power supply is connected to the external electrode layers of both the substrate members, and a negative side of the DC power supply is connected to the electrode frame. Then, in a vacuum atmosphere heated to a predetermined temperature, by applying a voltage from the DC power supply, a voltage is uniformly applied to the entire end face of the outer peripheral edge of the frame member. At the same time that the peripheral edge of the facing surface of the substrate member and the first contact surface of the frame member are anodically bonded,
The peripheral edge of the opposing surface of the substrate member and the second contact surface of the frame member are anodically bonded. 3. The method according to claim 1, wherein the frame member is made of a borosilicate glass containing Na ⁺ therein.