JPH08316085A - Semiconductor capacitor and trimming method for the capacitor - Google Patents

Abstract

PURPOSE: To provide a miniature semiconductor capacitor at low cost along with a trimming method. CONSTITUTION: A semiconductor capacitor 1 comprising a semiconductor element 10, an insulation layer 20 formed through degeneration of the surface layer, and an electrode layer 30 formed on the surface of the insulation layer 20 is mounted on a board. The electrode layer 30 is then trimmed by projecting laser light thereto thus adjusting the capacitance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor capacitor and its trimming method.

[0002]

2. Description of the Related Art Conventionally, for fine adjustment of frequency in electronic equipment such as communication equipment and measuring equipment, ceramics, plastic films, etc. are used as dielectrics, and electrodes are formed and fixed on one surface of the dielectrics. As an electrode, overlay the metal plate on the dielectric surface on the back side of the surface where the fixed electrode is formed and slide the metal plate to change the facing area between the fixed electrode and the metal plate to adjust the capacitance. Trimmer capacitors are widely used.

In recent years, as the demand for miniaturization of electronic devices has increased, a trimmer capacitor having a smaller size and a wider capacitance variable range has been demanded, but it is difficult to meet this demand with the trimmer capacitor having the above-mentioned configuration. It was Therefore, various proposals have been made to reduce the size of the trimmer capacitor and widen the variable range of capacitance. As one of them, there is a method of forming a fixed electrode inside the dielectric to reduce the thickness of the dielectric.

FIG. 6 is a sectional view of such a conventional trimmer capacitor. As shown in FIG. 6, the trimmer capacitor 60 includes a ceramic dielectric stator 61 having a fixed electrode 63 formed therein, a metal rotor 62 that rotates while contacting the dielectric stator 61, and a dielectric stator 6.
1 includes a terminal electrode 64 that is electrically connected to the fixed electrode 63 inside the unit 1, a terminal electrode 65 that is electrically connected to the metal rotor 62, and a resin case 66 that wraps the entire components.

FIG. 7 is a perspective view showing a metal rotor 62 used in the conventional trimmer capacitor shown in FIG. 6 in an upside down direction with respect to the metal rotor 62 shown in FIG.
FIG. 7 is a perspective view of a dielectric stator 61 used in the conventional trimmer capacitor shown in FIG. 6. As shown in FIGS. 6 and 7, the surface of the metal rotor 62 facing the dielectric stator 61 is a half-moon shaped contact surface 62 a due to the step 68.
And a non-contact surface 62b. The half-moon shaped contact surface 62a of the metal rotor 62 and the dielectric stator 61 are in contact with each other. Since the protrusion 69 for adjusting the step is provided on the non-contact surface 62b that is not in direct contact with the dielectric stator 61, the metal rotor 62 and the dielectric stator 61 slide smoothly. Also, the metal rotor 6
An adjusting groove 67 for trimming is provided on the surface of the second member opposite to the surface facing the dielectric stator 61, and a trimming jig (not shown) is applied to the adjusting groove 67 to rotate the metal rotor 62. By moving the metal rotor 62
Contact surface 62a of the fixed electrode 6 inside the dielectric stator 61
The area facing 3 is changed and the capacitance is adjusted.

[0006]

However, in the above trimmer capacitor, since the fixed electrode is formed inside the dielectric, the number of steps is increased and a complicated manufacturing process such as lamination of green sheets is required. In addition, there are many obstacles to mass production and cost reduction, such as limited materials used for the dielectric.

In view of the above circumstances, it is an object of the present invention to provide a small-sized and low-cost semiconductor capacitor and its trimming method.

[0008]

A semiconductor capacitor according to the present invention which achieves the above-mentioned object comprises a semiconductor element body, an insulating layer formed on the semiconductor element body by alteration of the surface layer of the semiconductor element body, and an insulating layer. And an electrode layer formed on the surface. Further, a method for trimming a semiconductor capacitor of the present invention which achieves the above object, a semiconductor element body, an insulating layer formed on the semiconductor element body by alteration of the surface layer of the semiconductor element body, and formed on the surface of the insulating layer. A semiconductor capacitor having an electrode layer is prepared, the semiconductor capacitor is mounted on a substrate, and the electrode layer is irradiated with laser light to trim the electrode layer.

[0009]

The semiconductor capacitor of the present invention, as described above,
The insulating layer on the semiconductor element body formed by modifying the surface layer of the semiconductor element body is used as the dielectric material of the capacitor, and the insulating layer that is the dielectric material, the electrode layer formed on the surface of the insulating layer, and the internal A capacitor is formed by the unaltered semiconductor portion inside the semiconductor element that acts as an electrode. Therefore, unlike the conventional trimmer capacitor, it is not necessary to form the internal electrode inside the dielectric, so that the semiconductor capacitor can be manufactured at low cost and with high productivity.

Further, since the dielectric formed by modifying the surface layer of the semiconductor body can be formed to have an extremely thin thickness, a semiconductor capacitor having a small size and a large capacitance can be easily manufactured. it can. After mounting the semiconductor capacitor of the present invention on a substrate, the capacitance of the capacitor can be trimmed to a desired capacitance by irradiating the electrode layer with laser light. in this case,
Since the capacitor itself has no moving parts, a small trimmer capacitor can be obtained. Further, since the structure of the trimmer capacitor is simple, it is possible to obtain a trimmer capacitor having a large capacitance and a wide capacitance variable range.

Further, the semiconductor capacitor trimming method of the present invention prepares the above semiconductor capacitor,
After mounting it on a substrate, the electrode layer of the semiconductor capacitor is irradiated with laser light to evaporate a part of the electrode layer to reduce the area of the electrode and reduce the capacitance of the capacitor to the desired capacitance. Since the trimming is performed, the change in capacitance due to vibration, heat, and other factors after trimming is smaller than that in the conventional trimming method that depends on the mechanism of the movable portion. Therefore, the trimmed capacitor operates extremely stably on the circuit.

[0012]

Embodiments of the present invention will be described below. FIG. 1 is a sectional view of a first embodiment of a semiconductor capacitor of the present invention. As shown in FIG. 1, this semiconductor capacitor 1
Is the semiconductor element body 10 and the insulating layer 20 formed on the semiconductor element body 10 by oxidizing the surface layer of the semiconductor element body 10.
And the electrode layer 30 formed on the surface of the insulating layer 20 and the terminal electrodes 4 formed on both ends 12 and 13 of the semiconductor body 10.
0.

The semiconductor element body 10 of the semiconductor capacitor 1 of this embodiment is made of a ceramic semiconductor, which is a ceramic semiconductor. The insulating layer 20 formed on the semiconductor body 10 functions as a dielectric of the capacitor, and the unoxidized semiconductor portion 11 inside the semiconductor body 10 faces the electrode layer 30 formed on the surface of the insulating layer 20. Acts as an electrode on the other side. The electrode layer 30 is not formed on the entire surface of the insulating layer 20, and as shown in FIG. 1, an electrode non-formation portion where the electrode layer 30 is not formed is formed at one end of the semiconductor element body 10. There is 21.

Since the insulating layer 20 is not formed on the end surface 12a of the semiconductor element body 10 on the electrode non-formation portion 21 side, the terminal electrode 40 formed on the end portion 12 of the semiconductor element body 10 is the semiconductor element body 10. It is electrically connected to the internal unoxidized semiconductor portion 11. On the other hand, since the end surface 13a of the semiconductor element body 10 is covered with the insulating layer 20, the semiconductor element body 1
The terminal electrode 40 formed at the end portion 13 of 0 is electrically insulated from the unoxidized semiconductor portion 11 inside the semiconductor body 10, and the terminal electrode 40 formed at the end portion 13 of the semiconductor body 10. The electrode 40 is formed on the surface of the insulating layer 20 and is electrically connected to the electrode layer 30.

Next, the semiconductor capacitor 1 of this embodiment is manufactured.
The manufacturing method will be described with reference to FIG. First, B
aTiO₃ Or SrTiO₃ Ceramic raw material powder
Nb at the end₂ O _Five And the like are added and mixed. Next
Then, add an organic binder such as Metroze to this mixed raw material powder.
After adding, kneading and extruding, the thickness is 1mm.
Make a green sheet of. Next, this green sea
Cut into 3.7 mm x 1.9 mm size chips
Then, the chips are made into semiconductors by reduction firing.
A ceramic semiconductor chip can be obtained. In addition,
Re-oxidizes the chip surface by firing the cup in the air
A semiconductor element body 10 having a film (insulating layer 20) is obtained.
It

Next, one end face 12a of the semiconductor body 10
Of the end surface 12 by physically polishing the insulating layer 20 of
The semiconductor portion 11 is exposed at a. Next, the semiconductor element body 1
0 is fixed to the workbench and the insulating layer 2 on the surface of the semiconductor element body 10 is fixed.
0 is coated with Ag electrode paste by a printing method, dried and baked. Next, both ends 12, 1 of the semiconductor element body 10
Ag / Pd terminal electrode paste is applied to each of the end faces 12a and 13a of No. 3 by a dipping method, dried and baked.

The Ag formed on the surface of the insulating layer 20
Ag / Pd formed on electrodes and both end faces 12a, 13a
The method of forming the terminal electrode is not limited to the above method, and may be replaced with another method such as a vapor deposition method. Further, the materials for these electrodes are not limited to the above materials. Next, a method of trimming the semiconductor capacitor of the present invention will be described.

FIG. 2 is a perspective view of a semiconductor capacitor for explaining the method of trimming the semiconductor capacitor of the present invention. As shown in FIG. 2, by irradiating the electrode layer 30 of the semiconductor capacitor 1 of this embodiment with a laser beam to evaporate the shaded portion 31 of the electrode layer 30 to reduce the electrode area,
The capacitance of the capacitor is trimmed to a predetermined capacitance.

Table 1 shows characteristic values of the trimmer capacitors trimmed by the above trimming method.

[0020]

[Table 1]

As shown in Table 1, this trimmer capacitor is small and has a wide capacitance variable range. In addition,
“Setting drift” in Table 1 means 2% after reducing the capacity by 20% by trimming by laser light irradiation.
The figure shows a change in electrostatic capacity before and after being left for 4 hours, which is shown as a percentage, and the change in electrostatic capacity after trimming of the semiconductor capacitor of this example is extremely small.

The temperature characteristics of the semiconductor capacitor of this embodiment,
That is, the rate of change (%) in capacitance due to temperature change can be further improved by changing the composition of the dielectric material. For example, a semiconductor capacitor having characteristics such as YF, YE, and YB can be manufactured by mixing BaTiO ₃ with various additives.

Further, by using a raw material containing TiO ₂ as a main component, a semiconductor capacitor having more excellent temperature characteristics can be manufactured. FIG. 3 is a sectional view of a second embodiment of the semiconductor capacitor of the present invention. As shown in FIG. 3, in this embodiment, the grain boundary layer 22 formed by diffusing the insulating agent is present in the surface layer of the semiconductor element body 10.

In order to form this grain boundary layer 22, an insulating agent is applied to the surface of the semiconductor element body 10 and baked to diffuse the insulating agent into the surface layer of the semiconductor element body 10. The surface layer portion of 10 is altered to form a thin grain boundary layer 22 (dielectric). This grain boundary insulation type semiconductor capacitor is characterized by having a large dielectric constant. The method is the same as that of the first embodiment except the method of forming the dielectric.

FIG. 4 shows a third embodiment of the semiconductor capacitor of the present invention.
3 is a cross-sectional view of the embodiment of FIG. In the third embodiment, the electrode layer 3
In the step of forming 0, the electrode layer 30 is formed and the surface layer of the semiconductor element body 10 is made into an insulator to form the insulating layer 20. In order to form this insulating layer 20, in the step of applying Ag paste on the surface of the semiconductor body 10 and baking it to form the electrode layer 30, the semiconductor body 10 is diffused in the Ag paste and diffused into the ceramic. An oxide, such as CuO, which turns into an insulator is mixed in advance. By doing so, the surface layer of the semiconductor element body 10 directly below the Ag paste is transformed into an insulator, and as shown in FIG. 4, the surface layer of the semiconductor element body 10 is transformed and the thin insulating layer 20 is formed. It is formed. This insulating layer 20 serves as a dielectric of the semiconductor capacitor 1.

The structure other than the insulating layer 20 is the same as that of the first embodiment. FIG. 5 is a sectional view of a semiconductor capacitor according to a fourth embodiment of the present invention. In the fourth embodiment, silicon, which is widely used as a material for memory elements, is used as the semiconductor element body 10. As shown in FIG. Insulation layer 2
0 is formed.

The structure other than the insulating layer 20 is the same as that of the first embodiment. Next, a method of manufacturing the semiconductor capacitor of the fourth embodiment shown in FIG. 5 will be described. Similar to the method for manufacturing a silicon wafer used as a material for a memory element of a computer, first, a silicon single crystal made into a semiconductor is manufactured, cut out as a substrate of the silicon single crystal, and the surface of the substrate is polished to reduce its thickness. After adjusting to 0.5 mm, the semiconductor element body 10 is manufactured by cutting into a size of 3.2 × 1.6 using a diamond blade. Next, the semiconductor element body 1
The longitudinal direction of 0 is made vertical and one end face 12a is fixed on the workbench, and then the surface of the semiconductor element body 10 is oxidized.
A 5000 Å SiO ₂ oxide film (insulating layer 20) is formed on the surface 0. End 12 of semiconductor body 10
Is in contact with the workbench, the end 12 of the semiconductor element body 10
The unoxidized semiconductor portion 11a remains in the vicinity. next,
After masking the semiconductor portion 11a, a metal such as Cr or Au is deposited on one surface of the semiconductor body 10 by a vacuum deposition method to form the electrode layer 30. Next, the terminal electrodes 40 are formed on both ends 12 and 13 of the semiconductor body 10 by a dipping method using a conductive resin adhesive.

Table 2 shows the characteristic values of the trimmer capacitor obtained by trimming the semiconductor capacitor of the fourth embodiment by the semiconductor capacitor trimming method of the present invention.

[0029]

[Table 2]

As shown in Table 2, this trimmer capacitor is small and has a wide capacitance variable range, and the temperature characteristic thereof is significantly improved as compared with the trimmer capacitor according to the first embodiment. You can see that In the fourth embodiment, the dielectric is formed by oxidizing the surface of the semiconductor silicon single crystal plate. However, in addition to this method, the surface of the semiconductor silicon single crystal plate is coated with a sol-gel solution. Then, the dielectric thin film may be formed by firing it, or by CVD (Ch
A dielectric thin film may be formed on the surface of the semiconductor silicon single crystal plate by using the electrical vapor deposition method.

[0031]

As described above, according to the semiconductor capacitor of the present invention, it is possible to obtain a small-sized and low-cost semiconductor capacitor which is easy to manufacture. When the semiconductor capacitor of the present invention is used as a trimmer capacitor, it is possible to obtain a compact trimmer capacitor having a large electrostatic capacitance and a wide variable capacitance range.

Further, according to the semiconductor capacitor trimming method of the present invention, it is possible to obtain a trimmer capacitor which has a small change in capacitance after trimming and operates extremely stably on a circuit.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a first embodiment of a semiconductor capacitor of the present invention.

FIG. 2 is a perspective view of a semiconductor capacitor for explaining a method for trimming a semiconductor capacitor of the present invention.

FIG. 3 is a sectional view of a second embodiment of the semiconductor capacitor of the present invention.

FIG. 4 is a sectional view of a semiconductor capacitor according to a third embodiment of the present invention.

FIG. 5 is a sectional view of a semiconductor capacitor according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view of a conventional semiconductor capacitor.

FIG. 7 is a perspective view of a metal rotor used in a conventional semiconductor capacitor.

FIG. 8 is a perspective view of a dielectric stator used in a conventional semiconductor capacitor.

[Explanation of symbols]

 1 Semiconductor Capacitor 10 Semiconductor Element 11 Semiconductor Part 12, 13 End 12a, 13a End Face 20 Insulating Layer 21 Electrode Non-Forming Part 22 Grain Boundary Layer 30 Electrode Layer 31 Diagonal Area 40 Terminal Electrode 60 Trimmer Capacitor 61 Dielectric Stator 62 Metal Rotor 62a contact surface 62b non-contact surface 63 fixed electrode 64,65 terminal electrode 66 resin case 67 adjustment groove 68 stepped portion 69 protrusion

Claims (2)

[Claims] 1. A semiconductor element body, an insulating layer formed on the semiconductor element body by alteration of a surface layer of the semiconductor element body, and an electrode layer formed on a surface of the insulating layer. And semiconductor capacitors. 2. A semiconductor capacitor comprising a semiconductor element body, an insulating layer formed on the semiconductor element body by alteration of the surface layer of the semiconductor element body, and an electrode layer formed on the surface of the insulating layer. A method for trimming a semiconductor capacitor, comprising: preparing and mounting the semiconductor capacitor on a substrate; and irradiating the electrode layer with laser light to trim the electrode layer.