JP2009039843A - Electric part and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric part high in reliability, and its manufacturing method. <P>SOLUTION: This electric part has a substrate 12 having a function element 11, a cover body 13 having a recessed part 13a larger in size than the function element 11, an adhesive layer 14 on which the recessed part 13a and the function element 11 are opposed to each other, and the cover body 13 is fastened to the substrate 12, and a sealing layer 15 to cover the outside of the adhesive layer 14 and smaller in gas permeability than the adhesive layer 14. The outside of the adhesive layer 14 is covered with the sealing layer 15 after an atmosphere in a cavity surrounded by the substrate 12 and the recessed part 13a is adjusted through the adhesive layer 14. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrical component and a manufacturing method thereof.

  The functional element having the movable part is hermetically sealed in the cavity in order to secure an operating space and to block the intrusion of outside air to protect the functional element.

  Conventionally, hermetic sealing is performed using a sealing material that does not transmit gas, such as a metal sealing method, a solder sealing method, and a glass sealing method (see, for example, Patent Document 1).

  In the electronic device disclosed in Patent Document 1, the device body and the lid are ultrasonically bonded to form a hermetic sealing structure, and then the strength of the ultrasonic bonding portion is increased and the effect of hermetic sealing is also increased. As described above, a sealing resin such as epoxy or polyimide is further provided outside the ultrasonic bonding portion.

However, the metal sealing method and the solder sealing method have a problem of affecting the characteristics of the functional element because a parasitic capacitance is generated between the functional element or the electric wiring and the sealing metal. Further, since the resin is inherently low in airtightness, there is a problem that only an auxiliary sealing effect is expected.
Since the glass sealing method has a high sealing temperature of 300 to 400 ° C., there is a problem that it is not suitable for hermetic sealing of functional elements having low heat resistance.
JP 2004-209585 A

  The present invention provides a highly reliable electrical component and a manufacturing method thereof.

  An electrical component of one embodiment of the present invention includes a substrate having a functional element, a lid having a concave portion larger in size than the functional element, the concave portion and the functional element are opposed to each other, and the lid is fixed to the substrate. It is characterized by comprising an adhesive layer and a sealing layer that covers the outside of the adhesive layer and has a lower gas permeability than the adhesive layer.

  In the method for manufacturing an electrical component of one embodiment of the present invention, a lid having a recess having a larger size than the functional element is fixed to a substrate having the functional element with an adhesive layer with the functional element facing the recess. A step, a step of adjusting the atmosphere in the cavity surrounded by the substrate and the recess through the adhesive layer, and the outside of the adhesive layer is covered with a sealing layer having a gas permeability smaller than that of the adhesive layer And a step of performing.

  According to the present invention, a highly reliable electrical component and a manufacturing method thereof can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

  An electrical component and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing an electrical component, and FIG. 2 is a cross-sectional view sequentially showing manufacturing steps of the electrical component.

  As shown in FIG. 1, the electrical component 10 of this embodiment includes a substrate 12 having a functional element 11, a lid 13 having a concave portion 13 a larger than the functional element 11, and the concave portion 13 a and the functional element 11 are opposed to each other. The adhesive layer 14 that fixes the lid 13 to the substrate 12 and the sealing layer 15 that covers the outside of the adhesive layer 14 and has a lower gas permeability than the adhesive layer 14 are provided.

  The substrate 12 is, for example, a silicon substrate. The functional element 11 is, for example, an electrostatically driven MEMS (Micro Electro Mechanical Systems) variable capacitor built in the substrate 12.

  The MEMS variable capacitor is a variable capacitor that utilizes the fact that, for example, when a voltage is applied to opposed aluminum electrodes, the distance between the aluminum electrodes changes due to electrostatic attraction.

  The lid 13 is a cap, for example, made of the same material as the substrate 12 and protects the functional element 11 from the outside. The recess 13 a formed in the lid 13 is a cavity for securing an operating space for the functional element 11.

  The inside of the cavity is kept in a dry atmosphere or a vacuum atmosphere so that the cleanliness of the aluminum electrode is impaired by harmful gas, for example, moisture, and the characteristics of the MEMS variable capacitor are not affected.

  The adhesive layer 14 is, for example, a silicone resin or an inorganic adhesive. As will be described later, after the lid 13 is fixed to the substrate 12 with the adhesive layer 14, the inside of the cavity is kept in a dry atmosphere or a vacuum atmosphere.

The gas permeability of the adhesive layer 14 is preferably as large as possible depending on the internal volume of the cavity so that moisture and harmful gas can pass through the adhesive layer 14 and be exhausted from the cavity in a short time.
The size of the cavity for storing the functional element represented by MEMS is, for example, about 2 × 2 × 0.04 mm, so that the gas permeability is practically larger than 1 × 10 ⁻¹² mol · m / m ² · s · Pa. Desirable above.

  The sealing layer 15 covers the entire surface of the substrate 12 and the lid 13 including the outside of the adhesive layer 14 so that the outside air containing moisture does not permeate the adhesive layer 14 and enter the cavity.

Therefore, the sealing layer 15 is a material having a gas permeability smaller than that of the adhesive layer 14, for example, an inorganic compound such as a silicon nitride film, a silicon oxide film, a silicon carbide film, a silicon oxynitride film, an aluminum oxide film, and an aluminum nitride film. A membrane is suitable.
These inorganic compound films are dense films, and their gas permeability is very small. For example, even in a thin film having a thickness of 1 μm or less, gas permeation can be ignored.

Next, a method for manufacturing the electrical component 10 will be described.
As shown in FIG. 2A, a substrate 12 having a plurality of functional elements 11 formed on a silicon wafer is prepared. A lid 13 is prepared in which a plurality of recesses 13a and stripe-like grooves 21 are formed between adjacent recesses 13a on a silicon wafer.

  Next, after applying, for example, a silicone resin as the adhesive 22 to the surface of the concave portion 13a and the groove 21 of the silicon wafer, the lid 13 is placed so that the functional element 11 and the concave portion 13a face the substrate 12. The lid 13 is placed on the substrate 12.

  Next, as shown in FIG. 2B, the adhesive 22 is cured by heating and pressing to cure the adhesive 22, and the substrate 12 and the lid 13 are fixed.

Next, as shown in FIG.2 (c), it grinds so that the board | substrate 12 and the cover body 13 may become predetermined thickness using a grinder, respectively.
The lid body 13 is ground to a thickness exceeding the groove 21, and the lid body 13 is separated into pieces by passing through the groove 21.

  At this time, since the process from the end of the process of FIG. 2B to the end of the process of FIG. 2C is performed in an air atmosphere, the moisture penetrates through the adhesive layer 14 of the lid 13 and is separated. And enters the cavity of the recess 13a.

Next, the substrate 12 with the lid 13 separated into pieces is housed in a container (not shown), and a dry gas is allowed to flow into the container to make the container have a low humidity atmosphere.
As a result, moisture that has permeated through the adhesive layer 14 and entered the cavity of the recess 13a permeates through the adhesive layer 14 due to the difference in partial pressure, diffuses outside, and is removed from the cavity.

  Next, as shown in FIG. 2D, in order to prevent moisture from entering again into the cavity of the recess 13a, the substrate 12 including the outside of the adhesive layer 14 and the individual lid 13 are separated. A sealing layer 15 is formed on the entire surface.

As the sealing layer 15, for example, SiH ₄ and NH ₃ are used as process gases, a film can be formed at a low temperature of about 250 to 300 ° C., and silicon having a thickness of about 1 μm is obtained by a plasma CVD (Chemical Vapor Deposition) method with good step coverage. A nitride film (SiN) is formed.
A silicon nitride film formed by a plasma CVD method is suitable as a sealing layer because it has a dense film quality and is excellent in moisture resistance and mechanical strength.

  Next, as shown in FIG. 3 (e), the substrate 12 is diced along the penetrated groove 21 using a diamond blade 23, and the substrate 12 is separated into individual pieces. Thereby, the electrical component 10 shown in FIG. 1 is obtained.

FIG. 3 is a diagram illustrating a result of calculating the time change of the humidity in the cavity of the recess 13a using the gas permeability of the adhesive layer 14 as a parameter.
The initial conditions used for the calculation were: temperature 30 ° C., initial humidity in the cavity 80%, external humidity 0%, cavity size 2 × 2 × 0.04 mm, adhesive layer 14 length 200 μm, adhesive layer The thickness of 14 is 10 μm.

As shown in FIG. 3, as the gas permeability increases from 5 × 10 ⁻¹⁵ mol · m / m ² · s · Pa to 1 × 10 ⁻¹² , the humidity in the cavity rapidly decreases.
Time humidity in the cavity is below 1%, when the gas permeability of ^{1 × 10 -12 mol · m /} m2 · s · Pa, is about 10 minutes, one in the manufacturing process of the electrical component 10 The processing time of the process is a practical value.

On the other hand, when the gas permeability is lower than 1 × 10 ⁻¹² mol · m / m ² · s · Pa, the time during which the humidity in the cavity is 1% or less is abruptly increased. It becomes scarce.

  Accordingly, the substrate 12 and the lid 13 can be fixed and the sealing layer 15 can be fixed by the adhesive 22 at a low temperature of 300 ° C. or lower, so that the functional element 11 having low heat resistance can be hermetically sealed. Is possible.

As a result, in the manufacturing process of the electrical component 10, it is possible to prevent the functional element 11 from being deteriorated in characteristics and broken due to insufficient heat resistance.
During use of the electrical component 10, it is possible to prevent the functional element 11 from being deteriorated in characteristics and broken down due to harmful gas.

  As described above, in this embodiment, after the substrate 12 and the lid 13 are fixed to each other by the adhesive layer 14 having a high gas permeability, harmful gas in the cavity of the recess 13a is removed through the adhesive layer 14. is doing.

  Thereafter, the outer side of the adhesive layer 14 is covered with a sealing layer 15 having a low gas permeability, thereby preventing the harmful gas from entering the cavity of the recess 13a through the adhesive layer 14.

  As a result, the substrate 12 and the lid body 13 are fixed using the adhesive 22 that can be cured at low temperature, and the outer side of the adhesive layer 14 is covered using the sealing layer 15 that can be formed at low temperature. The functional element 11 can be hermetically sealed.

  Therefore, there is no possibility that the characteristics of the functional element 11 will be deteriorated due to insufficient heat resistance in the manufacturing process, or that the functional element 11 may be damaged by harmful gases during use, and a highly reliable electrical component and a method for manufacturing the same can be obtained.

Although the case where the inside of the cavity of the recess 13a is dehumidified and held in a dry atmosphere has been described here, it may be held in a vacuum atmosphere.
If it is a vacuum atmosphere, there exists an advantage which can also remove harmful gases other than moisture, for example, oxidizing gas, corrosive gas, etc.

FIG. 4 is a diagram illustrating a result of calculating the time change of the degree of vacuum in the cavity of the recess 13a using the gas permeability of the adhesive layer 14 as a parameter.
The initial conditions used for the calculation were as follows: the temperature was 30 ° C., the initial pressure in the cavity was 1013 hPa, the external pressure was 1 hPa, the cavity size was 2 × 2 × 0.04 mm, the length of the adhesive layer 14 was 200 μm, and the thickness of the adhesive layer 14 Is 10 μm.

As shown in FIG. 4, as the gas permeability becomes large as ^{1 × 10 -12 mol · m /} m 2 · s · Pa from ^{1 × 10 -14 mol · m /} m 2 · s · Pa, in the cavity Pressure drops rapidly.
The time required for the pressure in the cavity to reach 1 hPa is about 30 minutes when the gas permeability is 1 × 10 ⁻¹² mol · m / m 2 · s · Pa.
On the other hand, when the gas permeability is lower than 1 × 10 ⁻¹² mol · m / m ² · s · Pa, the time for the humidity in the cavity to become 1 hPa increases abruptly.

  Although the case where the adhesive 22 serving as the adhesive layer 14 is a silicone resin has been described, similar effects can be obtained with an inorganic adhesive.

  Although the case where the sealing layer 15 is a silicon nitride film formed by a plasma CVD method has been described, a silicon oxide film, a silicon carbide film, a silicon oxynitride film, an aluminum oxide film, or an aluminum nitride film may be used.

When the sealing layer 15 is a silicon oxide film, it can be formed at a low temperature of about 250 to 300 ° C., for example, by a plasma CVD method using SiH ₄ and N ₂ O as process gases. The same applies to the silicon oxynitride film.
When the sealing layer 15 is a silicon carbide film, it can be formed at a low temperature of about 250 to 300 ° C., for example, by plasma CVD using SiH ₄ and CH ₄ as process gases.

Although the case where the sealing layer 15 is formed by the plasma CVD method has been described, it may be formed by a sputtering method or a vacuum evaporation method.
In the sputtering method and the vacuum evaporation method, the step coverage of the shadowed portion is poor, and therefore it is necessary to form the substrate 12 while rotating it uniformly by the planetary method.
The sputtering method or the vacuum deposition method has an advantage that the sealing layer 15 can be formed at a lower temperature than the plasma CVD method because it is not necessary to heat the substrate 12.

Although the case where the functional element 11 is an electrostatic drive type MEMS variable capacitor has been described, a piezoelectric drive type MEMS variable capacitor may be used.
In addition, other MEMS, for example, a thin film piezoelectric resonator (a thin film piezoelectric resonator formed on a substrate having a recess on the lower side of the piezoelectric thin film so as not to hinder the mechanical vibration by sandwiching the piezoelectric thin film between the lower electrode and the upper electrode) The same applies to FBAR (Film Bulk Acoustic Resonator).

Sectional drawing which shows the electrical component which concerns on the Example of this invention. Sectional drawing which shows the manufacturing process of the electrical component which concerns on the Example of this invention in order. The figure which shows the change of the humidity in the cavity of the electrical component which concerns on the Example of this invention. The figure which shows the change of the vacuum degree in the cavity of the electrical component which concerns on the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electrical component 11 Functional element 12 Board | substrate 13 Cover body 13a Recessed part 14 Adhesive layer 15 Sealing layer 21 Groove 22 Adhesive material 23 Blade

Claims (5)

A substrate having functional elements;
A lid having a recess having a larger size than the functional element;
The adhesive layer that the concave portion and the functional element face each other and the lid is fixed to the substrate;
A sealing layer that covers the outside of the adhesive layer and has a lower gas permeability than the adhesive layer;
An electrical component comprising:   The electrical component according to claim 1, wherein the adhesive layer is a silicone resin or an inorganic adhesive. The electrical component according to claim 1, wherein a gas permeability of the adhesive layer is greater than 1 × 10 ⁻¹² mol · m / m ² · s · Pa. A step of fixing a lid having a concave portion larger in size than the functional element to a substrate having the functional element with an adhesive layer facing the functional element and the concave portion;
Adjusting the atmosphere in the cavity surrounded by the substrate and the recess through the adhesive layer; and covering the outside of the adhesive layer with a sealing layer having a gas permeability smaller than that of the adhesive layer; ,
A method of manufacturing an electrical component comprising:   The method for manufacturing an electrical component according to claim 4, wherein the adhesive layer is a silicone resin or an inorganic adhesive.

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