JP2003100919A - Electronic device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic device, and its manufacturing method, in which a cap body for sustaining vacuum is provided for each cell utilizing an existing fabrication process of electronic device. SOLUTION: An Al film 151 is formed on a wafer 150 for cap and then patterned to form an annular film 144. A tubular part 142 surrounding a recess becoming a vacuum dome is formed by performing etching using the annular film 144 as a mask. Subsequently, a cut 152 is made in the substrate part 141 of the wafer 150 for cap and the wafer 150 for cap is mounted on a main wafer 100 on which an infrared area sensor is formed. Finally, the annular film 144 of the wafer 150 for cap is bonded to the annular film 118 of the main wafer 100 by compression thus forming an annular bonded part 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device constructed by enclosing a sensor, a transistor and the like in a reduced pressure atmosphere or an inert gas atmosphere.

[0002]

2. Description of the Related Art Conventionally, an electronic device such as an infrared sensor or a vacuum transistor that exhibits high performance in a vacuum atmosphere (or a reduced pressure atmosphere) is generally used by being enclosed in a container such as a hermetic seal or a ceramic. Has been. Such vacuum-packaged electronic devices include a so-called discrete device in which a single sensor is arranged and an integrated device in which a large number of sensors and transistors are arranged in an array.

On the other hand, an array of sensors and emitting elements is sealed in a vacuum atmosphere by a mounting method using a semiconductor device manufacturing process, rather than using a special container such as ceramics. Proposals have also been made to obtain electronic devices that are compact and highly integrated. For example, in International Publication WO95 / 17014, a cell array of detectors or radiation elements for infrared rays or the like is formed on a first wafer, and then a second wafer is arranged on the first wafer at a predetermined interval. , A method is disclosed in which the area where the cell array is arranged is sealed in a vacuum atmosphere by bonding the periphery of the cell array with solder while maintaining a vacuum state between both wafers.

[0004]

However, the technique of the above publication has the following problems.

First, when a large number of elements such as infrared detectors are arranged in an array, it is difficult to completely flatten the entire joint portion around the cell array, so that the pressing force required for thermocompression bonding naturally becomes excessive. Therefore, there is a possibility that the wafer may be damaged during the bonding, the vacuum state may be deteriorated due to the residual stress, or the device may not operate properly.

Secondly, if a bonding failure occurs in a part of the bonding portion for holding a large number of elements such as infrared detectors in a vacuum state, the vacuum state of the entire cell array is broken, so the device The whole becomes defective and the defective rate becomes high.

Thirdly, in soldering, since the organic material contained in the solder paste is degassed, the degree of vacuum in the internal space in which the cell array is arranged does not rise above a certain level. For example, there is a possibility that improvement in sensitivity of the infrared sensor or the like cannot be expected.

A first object of the present invention is to reduce the size and integration by providing means for enclosing in a decompressed atmosphere or an inert gas atmosphere in units of regions where detectors for infrared rays and electron-emitting devices are arranged. To provide an electronic device suitable for, a manufacturing method thereof, and the like.

A second object of the present invention is to improve the function of an electronic device such as an infrared sensor by providing means for increasing the degree of vacuum in the internal space where the cell array is arranged.

[0010]

An electronic device according to the present invention includes a body substrate having a cell region in which at least one element is arranged, a cap body mounted on the body substrate, and the plurality of cell regions. A cavity provided in at least one of the cell regions where the device is arranged, surrounded by the body substrate and the cap body and maintained in a reduced pressure atmosphere or an inert gas atmosphere, and the body substrate. And an annular joint portion that is provided between the cap body and the cap body and that shields the hollow portion from the external space.

As a result, it is possible to individually dispose elements, such as an infrared ray sensor and an electron emitting element, which require an atmosphere shielded from the external space, such as a reduced pressure atmosphere or an inert gas atmosphere, in the cavity. It is possible to obtain a structure suitable for both a portable electronic device and an integrated electronic device in which many elements are arranged.

Further, there is further provided a first annular film formed on the main body substrate and surrounding the element, and a second annular film formed on the cap body, wherein the annular joint portion is the first annular film. Since it is formed between the first and second annular films, it is possible to select the material forming the first and second annular films and provide a strong annular joint portion.

The materials for the first and second annular films are In,
Cu, Al, Au, Ag, Ti, W, Co, Ta, Al
A material selected from at least one of a Cu alloy and an oxide film is preferable.

The materials of the first and second annular films are preferably the same as each other.

The main body substrate is made of a semiconductor, and the element and the external circuit on the main body substrate are provided with an impurity diffusion layer formed across the first annular film in the main body substrate. The electrical connection between the elements and the external circuit can be improved by electrically connecting them to each other.

The cap body is provided with a concave portion forming the hollow portion and a tubular portion surrounding the concave portion, and the main body substrate is provided with an engaging portion that engages with the tubular portion. By doing so, it is possible to obtain an electronic device in which the positional relationship between the main body substrate and the cap body is stable and which has a highly reliable joint.

The electronic device is preferably an element selected from any one of an infrared sensor, a pressure sensor, an acceleration sensor and a vacuum transistor.

When the electronic device is an infrared sensor, the element provided on the main body substrate is a thermoelectric conversion element.

In this case, since the cap body has a Si substrate and a semiconductor layer provided on the Si substrate and having a bandgap smaller than 1.1 eV, the cap body can emit light close to visible light. Since it is possible to avoid the superposition of background signals, it is possible to secure a large dynamic range for infrared detection, and as a result, an electronic device suitable for detection of animals and people can be obtained.

In this case, since the uppermost layer of the cap body is composed of the Si layer on which the diffraction pattern serving as the Fresnel lens is formed, infrared rays can be focused on the thermoelectric conversion element of the infrared sensor, It is possible to improve the infrared detection efficiency.

The electronic device is an infrared detection sensor having a thermoelectric conversion element, a support member for supporting the thermoelectric conversion element, and a second cavity formed below the support member. Is preferred.

In this case, since no pillar or wall extending from the supporting member is provided inside the second hollow portion, it is possible to further improve the infrared detection sensitivity and the detection accuracy. You can

Further, since the second hollow portion is communicated with the hollow portion, it is possible to improve the infrared detection sensitivity and the detection accuracy.

An integrated electronic device can be obtained by providing a plurality of the annular joints so as to surround the plurality of cell regions.

In the first method for manufacturing an electronic device of the present invention, a body substrate having a plurality of cell regions in which at least one element is arranged and a cap substrate are prepared, and the body substrate and the cap substrate are prepared. A step (a) of forming a plurality of recesses surrounding at least one cell region of the plurality of cell regions in at least one of the plurality of cell regions; and a pressing force between the main body substrate and the cap substrate. A step of forming an annular joint between the main body substrate and the cap substrate so that at least some of the plurality of recesses remain as cavities blocked from the external space. (B) is included.

By this method, it is possible to manufacture both discrete type and integrated type electronic devices utilizing the existing manufacturing process of electronic devices such as Si process.
Moreover, since the cap body is mounted on each cell region individually to form the cavity, even if a bonding failure occurs in a part of the cell region,
Since other cell regions can be actually used, the yield can be improved in both the discrete type and the integrated type.

In the step (a), the main body substrate,
The cap substrate has a plurality of first and second surroundings surrounding the recess.
The second annular film is formed, and in the step (b), the first and second annular films are formed by forming the annular joint between the first and second annular films. It is possible to form a stronger annular joint by selecting the material.

The step (b) is performed by bonding using hydrogen bonding or metal bonding, or room temperature bonding, so that the cavity can be more reliably shielded from the external space.

In step (a), In, Cu, Al, Au, Ag and T are used as materials for the first and second annular films.
It is preferable to use a material selected from at least one of i, W, Co, Ta, an Al-Cu alloy, and an oxide film.

It is preferable to use the same materials as the materials for the first and second annular films.

Since the step (b) is performed without heating the main body substrate and the cap substrate to 450 ° C. or higher, the bonding can be performed without damaging the Al wiring.

In the step (a), the cap substrate is formed with slits for partitioning the cap substrate into a plurality of regions, so that pressing force is applied to the first and second annular films. Even when the wafers are warped when they are bonded to each other, it is possible to suppress the occurrence of a bonding failure due to locally applying a large stress.

In the step (a), the concave portion surrounded by each of the second annular films and the plurality of cylindrical portions surrounding the concave portion are formed in the cap substrate, so that the concave portion is formed only in the cap substrate. Since it may be formed, it is possible to avoid making the manufacturing process of the main body substrate difficult.

In the step (a), by preparing a main body substrate having an engaging portion that engages with the tubular portion of the cap substrate, the alignment accuracy of the first and second annular films is improved. Therefore, it is possible to obtain an electronic device with high reliability of bonding.

The step (b) is preferably performed in a reduced pressure atmosphere or an inert gas atmosphere.

Since the step (b) is carried out in a reduced pressure atmosphere having a pressure higher than 10 ^-4 Pa, it is possible to avoid the difficulty of maintaining a high vacuum state.
Practical and suitable for mass production can be performed.

After the step (c), a discrete electronic device can be obtained by further including a step of dividing the main body substrate into cell regions.

In a second method for manufacturing an electronic device of the present invention, a main body substrate having a plurality of cell regions in which at least one element is arranged and a cap substrate are prepared, and the main body substrate and the cap Step (a) of forming recesses surrounding at least one of the cell regions on at least one of the substrate and pressing force between the main substrate and the cap substrate to utilize hydrogen bonding or metal bonding. Joining,
Alternatively, the method includes a step (b) of forming an annular joint by room temperature bonding, wherein in the step (b), at least a part of the recess remains in the plurality of cell regions as a cavity that is shielded from an external space. Forming the annular joint.

By this method, the function of maintaining the atmosphere in the cavity at a desired atmosphere is improved as compared with the case of utilizing solder joining. For example, in an electronic device such as an infrared sensor in which a high vacuum atmosphere is preferable, the cavity can be kept in a high vacuum atmosphere.

In the step (a), a first annular film surrounding a plurality of cell regions is formed on the main body substrate, and a second annular film having a pattern substantially the same as the first annular film is formed on the cap substrate. By forming the annular film of, the materials forming the first and second annular portions can be selected to realize strong bonding.

In step (a), In, Cu, Al, Au, Ag and T are used as materials for the first and second annular films.
It is preferable to use a material selected from at least one of i, W, Co, Ta, an Al-Cu alloy, and an oxide film.

In this case, it is more preferable to use the same material as the material for the first and second annular films.

The step (b) is preferably performed without heating the main body substrate and the cap substrate to 450 ° C. or higher.

The step (a) can be performed so as to surround all the cell regions arranged in one electronic device by the first and second annular films.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Basic Structure of Electronic Device) FIG.
(A)-(d) is sectional drawing which shows roughly the basic structural example of the electronic device of this invention. Note that FIG.
The specific structure of the element arranged in the cell region 11 of the electronic device shown in (d) will be described later.

At least the region of the cell region 11 in which the elements are arranged is kept in a reduced pressure atmosphere by the cap body. Examples of elements provided in the cell area include an infrared sensor, a pressure sensor, an acceleration sensor, a flow velocity sensor, and a vacuum transistor.

The infrared sensor includes a thermal type such as a bolometer, a pyroelectric sensor, a thermopile, PbS, InSb,
It is roughly classified into a quantum form using HgCdTe or the like. Some bolometers utilize resistance changes of polysilicon, Ti, TiON, VO _x, and the like. Some thermopiles utilize the Seepec effect generated at the PN junction, and further utilize the transient characteristics of forward current such as a PN diode. For the pyroelectric infrared sensor, P
There is one that utilizes the change in the dielectric constant of materials such as ZT, BST, ZnO, and PbTiO ₃ . The quantum infrared sensor is
The current flowing through electronic excitation is detected. These infrared sensors generally have a characteristic that the characteristics are improved when they are sealed in a vacuum atmosphere or an inert gas atmosphere in the cap body.

Since the sensitivity of the pressure sensor and the acceleration sensor is improved by reducing the viscous resistance of air, it is known that the characteristics are improved by enclosing the cap sensor in a vacuum atmosphere or an inert gas atmosphere.

The number of elements arranged in one cell region of this type of sensor may be single or plural. further,
If necessary, a switching element (transistor) may also be provided in the cell region together with an element whose characteristics are improved by increasing the degree of vacuum.

—First Basic Structure Example— As shown in FIG. 1A, the electronic device of the first basic structure example includes a main body substrate 10 formed from a Si wafer and a desired region of the main body substrate 10. And a cap body 20A formed from a Si wafer for sealing in a reduced pressure atmosphere. The main body substrate 10 is provided with a cell region 11 in which a single element such as an infrared sensor and a circuit for supplying a signal to the element are arranged. On the other hand, the cap body 20A has a tubular portion 22 surrounding a substrate portion 21 made of silicon and a concave portion that is a cavity portion 23 held in a reduced pressure atmosphere.
It has and. That is, by using various bonding methods described later, a part of the cell region of the main body substrate 10 and the cylindrical portion 22 of the cap body 20A are coupled to each other in a reduced pressure atmosphere to form the cavity portion 23 held in the reduced pressure atmosphere. An annular joint 15 for sealing is formed. As a result, the elements in the cell region 11 are configured to exhibit their desired functions.

Here, as the structure of the concave portion, there is a space formed by removing a part of the flat substrate by etching to a certain depth, and a cylindrical portion which is a closed loop wall on the flat substrate. Therefore, there is a space surrounded by the tubular portion. Although FIG. 1 (a) discloses only a concave portion which is a space surrounded by the cylindrical portion 22, in the present invention, it is formed on the main body substrate or the cap substrate or both before forming the hollow portion. The structure of the recess is shown in FIG.
It is not limited to the form shown in (a). The same applies to each basic structure example and each embodiment described below.

As a method of forming the cylindrical portion surrounding the concave portion, a method of forming a cylindrical portion surrounding the concave portion by leaving a closed loop region of the flat substrate and removing the other region to a certain depth, There is a method of forming a cylindrical portion surrounding a concave portion by stacking closed loop walls on a flat substrate, and either method may be used.

-Second Basic Structure Example- As shown in FIG. 1B, the cap body 20B in the electronic device of the second basic structure example has a substrate portion 21 and a cavity portion 23 held in a reduced pressure atmosphere. 2 that encloses the recess that becomes
In addition to 2, the Ge filter portion 24 made of Ge having a thickness of about 3 μm is provided. The structure of the main body substrate 10 in the second basic structure example is the same as that of the main body substrate 10 in the first basic structure example. In this case, the substrate portion 21 has a wavelength of about 0.
While the light (infrared ray) having a wavelength of 8 μm or more is easily transmitted, the Ge filter portion 24 transmits only the light (infrared ray) having a wavelength of approximately 1.4 μm or more, and is close to visible light having a wavelength of approximately 1.4 μm or less. Blocks light in the wavelength range.

Therefore, the second basic structure example is applied to a device in which an infrared sensor is built in the cell region 11, so that a change in the current amount of a transistor in an electronic circuit due to the incidence of light close to visible light can be considered. It is possible to prevent erroneous detection due to it. In particular, infrared sensors are used to detect human bodies, animals, etc. at night, but light close to visible light such as cars and lighting excites carriers in the active regions of transistors in electronic circuits, resulting in superposition of background signals. This is because the detection margin of the infrared component may be reduced.

In order to epitaxially grow a Ge layer on a silicon wafer, Si can be grown on the silicon wafer.
_{The 1-x} Ge _x layer may be epitaxially grown so that the Ge component ratio x changes from 0 to 1, and then the Ge layer may be epitaxially grown to a predetermined thickness.

A Si _1-x Ge _x layer is formed on the Ge layer by G
After the epitaxial growth is performed so that the e component ratio x changes from 1 to 0, the Si layer may be epitaxially grown to a predetermined thickness. If the subsequent steps are carried out with the Ge layer exposed, the manufacturing apparatus may be contaminated with Ge. If the surface layer is composed of a Si layer, it may be necessary to perform electronic processing for the next Fresnel lens formation. It is preferable that the Ge layer is not exposed on the outermost surface in that the device manufacturing process can be used as it is.

The layer functioning as a filter may be made of a material containing an element other than Ge. In particular, a material having a bandgap smaller than the bandgap of 1.1 eV of Si absorbs light in a wavelength range longer than 0.8 μm (mainly near infrared rays), and thus diffuses impurities such as transistors arranged in the cell. It is possible to avoid problems caused by exciting carriers in the layer.

-Third Basic Structure Example- As shown in FIG. 1C, the cap body 20C in the electronic device of the third basic structure example has a substrate portion 21 and a cavity portion 23 held in a reduced pressure atmosphere. 2 that encloses the recess that becomes
In addition to 2, the Ge filter section 24 and the Si layer 25 having a grating pattern 27, which becomes a Fresnel lens having a convex lens function, is engraved on the surface thereof. The structure of the main body substrate 10 in the third basic structure example is the same as that of the main body substrate 10 in the first basic structure example. The third basic structure example is suitable for a device incorporating an infrared sensor for the same reason as the second basic structure example, and in particular, the convex lens function of the lattice pattern on the surface makes light effective at the existing position of the resistor. Therefore, it is possible to obtain an electronic device suitable for miniaturization and high performance.

In the atmosphere, the wavelength range of electromagnetic waves is 3 μm to 5 μm.
And 8 μm to 10 μm, there is a portion with high infrared transmittance called “atmosphere window”, and infrared rays pass through that band, but it is difficult to detect infrared rays due to disturbance noise in portions other than the atmospheric window. It becomes an area. The wavelength range of infrared rays emitted from the human body or animal body is 3 μm to 10 μm.
Since it is μm, by providing the Ge filter layer 24, while avoiding erroneous detection due to light in the range of 0.8 μm to 1.4 μm close to visible light, the detection of the person or animal targeted by the infrared sensor can be performed. It can be done accurately.

In place of the Ge filter layer, SiGe
A filter layer (composition Si _1-x Ge _x ) may be provided. In that case, the frequency band of infrared rays that can be blocked by the Ge component ratio x varies in the range of 0.8 μm to 1.4 μm. Therefore, by providing the SiGe filter layer, there is an advantage that the cutoff frequency range can be adjusted according to the purpose.

-Fourth Basic Structure Example- As shown in FIG. 1D, in the electronic device of the fourth basic structure example, a main body substrate 10 made of Si and a desired region of the main body substrate 10 are decompressed in an atmosphere. A cap body 20D made of Si for sealing the inside is provided. On the main body substrate 10, a large number of cell regions 1 in which one element such as an infrared sensor and a circuit for supplying a signal to the element are arranged.
1 is provided. On the other hand, the cap body 20D includes a substrate portion 21 and a large number of tubular portions 22 that surround a concave portion that serves as a hollow portion 23 that is held in a reduced pressure atmosphere. That is, by using various bonding methods described later, a part of each cell region 11 of the main body substrate 10 and each cylindrical portion 22 of the cap body 20D are coupled to each other in a depressurized atmosphere to form a closed loop annular bonding portion 1.
5 is formed so that each cavity 23 can be maintained in a reduced pressure atmosphere and the element in each cell region 11 can exhibit a desired function.

The substrate portion 21 has a notch for partitioning the substrate portion 21 into cell regions, and each cell region is divided at the notch during or after joining. However, it may not be divided at the cut portion. Even in that case, even if there is a slight difference in pressing force (compression force) between cells due to the bonding thickness of each cap body or the deformation of the wafer, the elastic deformation at the notch causes the bonding in each cell. The pressing force of is made as uniform as possible.

Further, in FIG. 1 (d), the cap body 20D has only the substrate portion 21, but it may have a Ge cap portion, and further has a lens function such as a Fresnel lens on the surface. You may have it.

FIGS. 1A to 1D show a state in which the main body substrate and the cap body are bonded to each other by bonding Si to each other. However, in general, the manufacturing process is easier using the joining of metals than the joining of Si. Therefore, an example of the structure of the joint will be described below.

(Structural example of the joint) FIGS. 2 (a) to 2 (d)
FIG. 3 is a cross-sectional view schematically showing a structural example of a bonding portion for holding a vacuum of the electronic device of the present invention.

The meanings of the hydrogen bond bonding, the metal bond bonding, and the room temperature bonding used in the present invention will be described below.

The hydrogen bonding is carried out in the range from atmospheric pressure to a low vacuum state of about 10 ⁻⁴ Pa. The hydrogen bonding may be unheated or heated. Metal bond is 100
There are cases where the pressure is applied to about 0 Pa, cases where the pressure is lower than 10 ⁻⁸ to an ultra-vacuum state, and there are cases where the sample is heated to a high temperature and cases where it is not heated. Room temperature bonding is a method of directly bonding members to be bonded at an atomic level without heating, and ranges from a relatively low vacuum state of about 10 ^-4 Pa to an ultra-vacuum state of a pressure lower than 10 ^-8 Pa. Done in. By the room temperature bonding, it is possible to bond the members to be joined made of a material other than metal such as metals, ceramics or silicon. Further, room temperature bonding includes atomic level direct bonding (performed in the range of 10 ⁻⁶ to 10 ⁻⁹ Pa) and bonding using metal bonding.

-Structural Example of First Bonding Section- As shown in FIG. 2A, in the structural example of the first bonding section,
An annular film 12 made of a metal (for example, aluminum (Al)) as a bonding material is provided on the main body substrate 10, and a metal (for example, Al) as a bonding material is provided at the tip of the tubular portion 22 of the cap body 20. An annular film 26 made of, for example, is provided. Then, in the depressurized atmosphere, each annular film 12, 26
The cavity 23 on the cell region 11 is sealed in a reduced-pressure atmosphere by forming a ring-shaped joint 15 by bonding the two by hydrogen bonding or the like.

In addition, in the structural example of the first joint portion and the structural examples of the second to fourth joint portions to be described later, the metal as the joining material is In, Cu, Au, A in addition to Al.
There are metals or alloys, such as g, Ti, W, Co, Ta, Al-Cu alloys, and metal bonds between these metals, between metals and alloys, or between alloys can be utilized. Further, it is possible to use a material other than metal as the bonding material. For example, it is possible to utilize hydrogen bonds between silicon oxide films, between silicon oxide films and Si, or between Si.

It can be said that the present invention is suitable for the present invention in the case of performing the bonding utilizing the metal bond or the hydrogen bond, or the room temperature bonding, because the bonding is easy at a low temperature and a low vacuum atmosphere.

In the structural examples of the first joint portion and the structural examples of the second to fourth joint portions which will be described later, when utilizing hydrogen bonds between Si, the respective annular films 12 and 26 are formed. There is no need to provide it.

-Structural Example of Second Bonded Section- As shown in FIG. 2B, in the structural example of the second bonded section,
An annular protrusion 14 made of an insulating film is provided on the main body substrate 10, and an annular film 12 is provided on a region inside the annular protrusion 14 of the cell region 11. On the other hand, an annular film 26 is provided at the tip of the tubular portion 22 of the cap body 20. Then, in the depressurized atmosphere, the tubular portion 22 is moved to
4, the annular membranes 12 and 26 are joined to each other to form the annular joint portion 15, so that the cell region 1 is formed.
The cavity 23 above 1 is sealed in a reduced pressure atmosphere. That is, the annular protrusion 14 functions as an engaging portion that engages with the tubular portion 22. However, although the main body substrate 10 is provided with a recess having an inner side surface that engages with the outer side surface of the tubular portion 22 as an engaging portion, the inner side surface of the tubular portion 22 and the outer side surface of the engaging portion of the main body substrate are It may be engaged.

According to this structural example of the joint portion, the cap body 20 can be reliably fixed on the main body substrate 10. Therefore, the structural example of the joint portion is particularly suitable for an electronic device having a plurality of cell regions 11. It has a different structure.

-Structural Example of Third Bonding Section- As shown in FIG. 2C, in the structural example of the third bonding section,
On the main body substrate 10, an annular protrusion 14 made of an insulator whose inner surface is a tapered surface is provided.
The annular film 12 is provided on a region inside the annular protrusion 14 of. On the other hand, the outer surface of the cylindrical portion 22 of the cap body 20 is also a tapered surface having substantially the same inclination as the tapered surface of the inner surface of the annular protruding portion 14, and the annular film 26 is provided at the tip of the cylindrical portion 22.
Is provided. Then, in a depressurized atmosphere, the annular joints 15 are formed by joining the annular membranes 12 and 26 in a state where the inner surface of the annular projection 14 and the outer surface of the tubular portion 22 are fitted together. Cavity 2 on the cell region 11
3 is sealed in a reduced pressure atmosphere. Also in this case, the annular protrusion 14 functions as an engaging portion that engages with the tubular portion 22. However, a recess having an inner side surface that engages with the outer side surface of the tubular portion 22 may be provided in the main body substrate 10 as an engaging portion. Further, the inner surface of the tubular portion 22 may be engaged with the outer surface of the engaging portion of the main body substrate.

According to the structural example of this joint, it is easy to align the cap body 20 on the main body substrate 10, and this structural example of the joint is particularly suitable for an electronic device having a plurality of cell regions 11. It has a different structure.

-Structural Example of Fourth Bonded Section- As shown in FIG. 2D, in the structural example of the fourth bonded section,
An annular protrusion 14 made of an insulating material having a stepped surface on the inner surface is provided on the main body substrate 10, and the cell region 11 is provided.
The annular film 12 is provided on a region inside the annular protruding portion 14. On the other hand, the outer surface of the cylindrical portion 22 of the cap body 20 is a stepped surface that engages with the stepped surface of the inner side surface of the annular protrusion 14, and the annular film 26 is provided at the tip of the cylindrical portion 22. . Then, in the reduced pressure atmosphere, the annular protrusion 14
With the inner surface of and the outer surface of the tubular portion 22 fitted,
By forming the annular joint 15 by joining the annular films 12 and 26 to each other, the cavity 23 on the cell region 11 is sealed in a reduced pressure atmosphere.

In this case as well, the annular projection 14 has the cylindrical portion 2
It functions as an engaging portion that engages with 2. However, the tubular portion 22
Alternatively, a stepped outer surface may be provided on the main body substrate 10, and a recess having a stepped inner surface that engages with the main body substrate 10 may be provided as an engaging portion. Further, the cylindrical portion 22 may be provided with a stepped inner surface, and the main body substrate may be provided with an engaging portion having a stepped outer surface.

According to this structural example of the joint, it is easy to align the cap body 20 on the main body substrate 10, and this structural example of the joint is particularly suitable for an electronic device having a plurality of cell regions 11. It has a different structure.

(Electrical Connection Structure) FIGS. 3A and 3B
FIG. 4A is a plan view and a cross-sectional view showing, in order, an example of an electrical connection structure suitable for the electronic device of the present invention. However, FIG. 3A shows a planar structure of the electronic device without the cap body.

As shown in FIGS. 3 (a) and 3 (b), the main body substrate 10 and the cap body 20 are mechanically connected to each other by bonding the annular films 12 and 26 to each other, and a vacuum state is provided between them. A cavity portion 23 held by is formed. Further, on the main body substrate 10, for example, an element 40 such as a bolometer shown by a broken line, a gate electrode 31, a source region 32.
And an N-channel type switching transistor 30 having a drain region 33. The switching transistor 30 controls the electrical connection between the element 40 and an external circuit. Then, the on / off of the electrical connection between the element 40 arranged in the region sealed by the cap body 20 and the external circuit is controlled. The drain region 33 and the gate electrode 31 of the switching transistor 30 are provided in the region surrounded by the cap body 20. The source region 32 is shown in FIG.
As shown in FIG. 4, the annular films 12 and 26 are formed in the substrate body 10 so as to cross the annular films 12 and 26. Also, the cap body 20
Impurity diffusion layers (N + type diffusion layers) 32, 35, which are formed so as to traverse the annular films 12, 26 in the substrate body 10 and function as wirings, in a region located immediately below the cylindrical portion of the.
36 are provided.

An inter-layer insulating film 41 made of silicon oxide covering the switching transistor 30 and the main substrate 10 and a passivation film 42 covering the inter-layer insulating film 41 are formed on the main substrate 10. There is. Further, the gate electrode 31 of the switching transistor 30
And a contact 31a connecting the impurity diffusion layer 36 and
A first wiring 51a connecting the source region 32 of the switching transistor 30 and an external circuit (not shown) to each other.
A second wiring 51b connecting the impurity diffusion layer 36 and an external circuit (not shown) to each other, and a third wiring connecting the drain region 33 of the switching transistor 30 and the element 40.
A wiring 51c, a fourth wiring 51d that connects the element 40 and the impurity diffusion layer 35 to each other, and a fifth wiring 51e that connects the impurity diffusion layer 35 and an external circuit (not shown) to each other are provided. That is, the element 40 and the switching transistor 30 are connected via the third wiring 51c and the drain region 33. Further, the element 40 is the fourth
It is connected to an external circuit via the wiring 51d, the impurity diffusion layer 35, and the fifth wiring 51e.

By adopting such an electrical connection structure, there is no metal wiring immediately below the annular joint portion 15 existing between the annular film 26 of the cap body 20 and the annular film 12 of the main body substrate 10. Therefore, due to the pressing force (crimping force) when connecting the annular films, the wiring may be broken and broken,
It is possible to effectively prevent the reliability of the connection from being deteriorated by a part of the breakage. Further, since it becomes easy to cover the interlayer insulating film 41 with the passivation film 42 in the hollow portion 23, it is possible to prevent gas and the like generated from the interlayer insulating film 41 from entering the hollow portion 23, The vacuum state of the hollow portion 23 can be maintained well.

The external circuit may be formed on the main body substrate 10 in a region not covered with the cap body 20, or may be provided in a portion different from the infrared sensor.

Further, in the structure of the electronic device shown in FIGS. 3A and 3B, the cap body 20 is provided so as to surround the element 40 in the cell region and the switching transistor 30 (particularly the drain region 33). ing. As described above, by providing the Ge layer having a filter function in the cap body 20, it is possible to avoid the occurrence of defects due to carriers excited in the drain region of the switching transistor 30 in the cell region. Further, even if the Ge layer is not provided on the cap body 20, a filter made of Ge or the like may be provided at a position that prevents light from at least entering the switching transistor 30. Furthermore, if the cap body 20 is not provided with a filter portion such as a Ge layer, it is not necessary to surround the switching transistor 30 (particularly the drain region) with the cap body 20.

(First Embodiment) Next, a first embodiment, which is an example in which the electronic device of the present invention is applied to a discrete infrared sensor, will be described.

FIGS. 4A and 4B are a sectional view and an electric circuit diagram of the infrared sensor according to the first embodiment of the present invention.

As shown in FIG. 4A, the infrared sensor according to the present embodiment has a Si substrate 110 having a thickness of about 300 μm.
A resistive element (bolometer) 120 provided on the Si substrate 110, a switching transistor 130 formed on the Si substrate 110 for turning on / off a current to the resistive element 120, and a resistive element 120. Cap body 14 for holding the mounted area in a reduced pressure atmosphere
It has 0 and. The size of this infrared sensor is
It is about several mm. A resistor 111 patterned in a zigzag pattern and a resistor 11 are formed on the Si substrate 110.
1 is provided with a silicon nitride film 112 and a silicon oxide film 113, and a BPSG film 116 and a passivation film (silicon nitride film) 117 that cover the resistor 111. Silicon oxide film 113, BPSG film 11
6 and the silicon nitride film 112 are patterned in a zigzag shape together with the resistor 111, and extend to above the Si substrate 110. Zigzag-shaped resistor 11
1, below the silicon oxide film 113, the BPSG film 116 and the passivation film 117, and above the passivation film 117, the cavity portions 119 and 143 held in vacuum are provided, respectively, the cavity portions 119 and 143, the silicon oxide film 113, BPSG
The films 116 and the silicon nitride film 112 are connected to each other through the gaps and the sides of the integrated portions. Then, on the cavity 119, the resistor 111, the silicon oxide film 113, the BPSG film 116, and the passivation film 11 are formed.
7 and the silicon nitride film 112 are in a state of being folded in a zigzag shape.

As the material of the resistor 111, there are Ti, TiO, polysilicon, Pt and the like, and any of them may be used.

The annular film 11 made of a soft metal material (aluminum or the like) is formed on the portion of the passivation film 117 located below the cylindrical portion 142 of the cap body 140.
8 is provided, and an annular film 144 made of a soft metal material (aluminum or the like) is also provided at the tip of the tubular portion 142, and the annular joint portion 15 formed between the both joint portions 118 and 142 allows the cap to be formed. Body 140 and Si substrate 110
The cavities 119 and 143 existing between and are held in a reduced pressure atmosphere (vacuum state). That is, the cavity 11
Due to the presence of 9,143, the resistor 111 is
It is thermally insulated from the substrate 110 and is configured to maintain a high conversion efficiency from infrared rays to heat.

Further, the substrate portion 141 of the cap body 140
Is about 3 μm thick on a silicon substrate of about 300 μm thick.
m, and a Si layer having a Fresnel lens formed on the surface and having a thickness of about 1 μm are epitaxially grown. A hollow portion having a depth of several μm or more is formed by the cylindrical portion 142 of the cap body 140. The window portion may be thinned by etching or the like.

Further, the switching transistor 130
Includes a source region 131, a drain region 132, and a gate electrode 133. Then, the drain region 132
Is formed below the cylindrical portion 142 of the cap body 140, and the drain region 132 is configured to function as a wiring for connecting a signal between the resistor 111 sealed in a vacuum state and an external member. There is.

Although not shown in FIG. 4A, a Peltier element for cooling the resistance element is attached to the lower surface of the Si substrate 110. This Peltier element is an element that utilizes the heat absorption effect associated with the movement of carriers that pass through the Schottky contact portion, and various Peltier elements having a known structure can be used in the present embodiment.

As shown in FIG. 4B, one end of the resistor 111 is connected to the wiring 135 for supplying the power supply voltage Vdd,
The other end of the resistor 111 has the switching transistor 130.
Of the drain region 132. Further, an ON / OFF switching signal is input to the gate of the switching transistor 130 via the wiring 136, and the source of the switching transistor 130 is connected to the resistor 111 via the wiring 138 having a standard resistance at the other end. The switching transistor 130 is connected to a detection unit (not shown) for detecting the amount of received infrared rays, and the substrate region of the switching transistor 130 is connected to the ground, which supplies the ground voltage Vss, via the wiring 137. That is, when the temperature of the resistor 111 changes according to the amount of infrared rays and the resistance value changes, the potential of the wiring 138 changes, so the amount of infrared rays is detected from this change in potential.

In the discrete infrared sensor, an operational amplifier for amplifying the output from the bolometer or the like may be provided on the substrate. In that case, in addition to the bolometer and the switching transistor of the present embodiment,
The operational amplifier can be arranged in the area sealed by the cap body.

Next, an example of the manufacturing process of the infrared sensor in this embodiment will be described. 5 (a)-(f)
FIG. 4A is a cross-sectional view showing a manufacturing process of the infrared sensor according to the first embodiment (see FIGS. 4A and 4B) of the present invention. Further, FIGS. 6A to 6E are plan views showing a process of forming the bolometer and its peripheral region. And FIG.
6A is a sectional view taken along line Va-Va shown in FIG. 6C, FIG. 5B is a sectional view taken along line Vb-Vb shown in FIG. 6D,
FIG. 5D is a sectional view taken along the line Vd-Vd shown in FIG.

FIG. 13 is a sectional view showing the overall structure of the infrared sensor according to this embodiment. As shown in the figure, the infrared sensor includes a sensor region Rsens in which cell regions having resistive elements such as bolometers and switching transistors are arranged in an array, and a transistor region for controlling current and operation in each cell region. And a peripheral circuit region Rperi (control circuit) formed by disposing (see FIG. 9). However, in the present embodiment, only the structural change in the sensor region Rsens in the manufacturing process will be described. Changes in the structure of the peripheral circuit region Rperi during the manufacturing process are irrelevant to the features of the present invention and are well known in various CMOs.
The S step can be used.

First, in the step shown in FIG. 5A, a large number of holes 112x as shown in FIG. 6A are formed on the Si substrate 110.
A flat plate-shaped silicon nitride film 112 is formed. Next, using the silicon nitride film 112 as a mask, the Si substrate 110 is dry-etched to form a bottomed hole just below the hole 112x, and then the hole is enlarged in the horizontal and vertical directions by wet etching. A cavity 119x having a depth of about 1 μm is formed as shown in FIG. At this time, in FIG. 5A, it is drawn that the wall portions 110x always exist between the small hollow portions 119x, but the hollow portions 119x are connected to each other below the approaching holes 112x. Then, it may be a relatively large cavity.

Then, when the polysilicon film 113 is formed on the silicon nitride film 112, the polysilicon film 11 is formed.
Since 3 does not completely cover the hole 112x, FIG.
As shown in (c), a small hole 113x is also formed in the polysilicon film 113.

Next, in the step shown in FIG. 5B, the polysilicon film 113 is thermally oxidized to form a silicon oxide film 113a. The silicon oxide film 113a is used to form the holes 1
13x is blocked. Further, the silicon oxide film 113a
After depositing a resistor film made of a conductor such as Ti on the
This is patterned to form a resistor 111 having a serpentine pattern as shown in FIG.

Then, after depositing a polysilicon film on the substrate, the polysilicon film is patterned to form the gate electrode 1.
33 is formed. Then, impurities (for example, n-type impurities such as arsenic and phosphorus) are implanted into regions of the Si substrate 110 located on both sides of the gate electrode 133, and the source region 1
31 and the drain region 132 are formed.

At this time, MIS transistors in the peripheral transistor region (not shown) other than the sensor region are also formed at the same time. After that, although not shown, some layers of interlayer insulating films and wiring layers (that is, multilayer wiring layers) covering the already formed members in the sensor region and the peripheral transistor region are formed on the substrate.
To form. However, in this embodiment, in this step, only some of the interlayer insulating films are deposited in the sensor region without forming the wiring layer.

Next, in the step shown in FIG. 5C, the gate electrode 133 and the resistor 11 are formed on the interlayer insulating film in the sensor region.
A silicon oxide film 116 is deposited so as to cover the entire upper surface of the substrate including 1.

Next, in the step shown in FIGS. 5D and 6E, the portion of the silicon oxide film 116 located in the gap between the resistors 111 is removed. At this time, a part of the silicon oxide film 116 remains and covers the resistor 111. Then, a passivation film 117 made of silicon nitride is deposited on the substrate. The passivation film 117 is for preventing moisture, humidity and the like from entering the resistor 111 and the switching transistor 130. After that, of the passivation film 117, the silicon oxide film 113, and the silicon nitride film 112, the portions located in the gaps between the resistors 111 are removed. This completes the formation of the resistance element (bolometer) 120. At this time, the wall portion 110x existing between the hollow portions 119x is also removed, and the wide hollow portion 119 is formed.
The cavity 119 communicates with the external space through the hole Het formed by this etching. In addition, the resistor 111 includes the silicon oxide film 113 and the silicon oxide film 11.
6 and the passivation film 117.

Incidentally, also in the peripheral transistor region (not shown), this passivation film 117 can be formed so as to cover the uppermost layer of the multilayer wiring. This passivation film is extremely commonly formed in the LSI manufacturing process. In the present embodiment, the passivation film 117 in the sensor region can be formed in the same process as the passivation film covering the peripheral transistor region and the same nitride film.

Next, in the step shown in FIG. 5E, the resistor 111 and the switching transistor 130 are formed on the passivation film 117 on the region around the resistor 111.
A ring-shaped film 118 made of metal (aluminum (Al)) having a thickness of about 600 nm is formed so as to surround the ring. At this time, part of the annular film 118 is the switching transistor 1.
It is located above the 30 source regions 131.

Although not shown in FIG. 5E, wirings 51a to 51 as shown in FIGS. 3A and 3B are also provided.
e is formed. That is, the impurity diffusion layer (including the source / drain regions) and the resistor 111 of the bolometer are penetrated through the passivation film 117 and the silicon oxide film 116.
After forming a contact hole reaching to, the contact hole is filled and a wiring extending on the passivation film is formed.

Next, in the step shown in FIG. 5 (f), a substrate portion 141 serving as a window for passing infrared rays in the wavelength region of 1.4 μm or more and a cylindrical portion 142 surrounding the recess are formed on the silicon substrate.
A cap body 140 having an annular film 144 made of Al and provided on the tip of the tubular portion 142 is prepared. Then, the annular film 144 on the cap body 140 and the Si substrate 1
The annular film 118 on 10 is aligned and the two are bonded to each other to form the annular joint 15. At this time, the entire cell region has substantially the same planar shape and circuit structure as shown in FIGS. 3 (a) and 3 (b).

Here, each of the annular films 118 and 144 is made of Al.
It is formed by patterning the Al film formed by sputtering. Then, the annular film 118,
FAB (First Atom Beam) processing in 144, that is, Ar
A dangling bond is exposed on the surface of Al by performing a treatment of irradiating atoms, and then both are bonded by pressure bonding. Details of this joining step will be described later.

In this embodiment, the manufacturing process of an infrared sensor using a resistor called a bolometer has been described, but the method of forming a bolometer that can be used in the present invention is not limited to this manufacturing process. Absent. Also, other types of infrared sensors can be utilized. In that case, a completely different manufacturing process is performed, but in any case, since the feature of the present invention is not the structure of the bolometer itself, the present invention can be applied to other types of infrared sensors, pressure sensors, acceleration sensors. The description of the manufacturing process when applied is omitted.

As described above, the following two effects can be obtained by the manufacturing process shown in FIGS.

First, in the step shown in FIGS. 5D and 6E, the wall portion 110 existing between the hollow portions 119x is formed.
Since x is also removed and a wide cavity 119 is formed,
Since the pillars and walls that connect the upper resistance element 120 and the lower substrate area do not exist in the cavity 119, heat dissipation of the resistance element 120 can be minimized, and the detection sensitivity of the infrared sensor and The detection accuracy can be improved.

Second, since the cavity 119 formed below the resistance element 120 by the hole Het communicates with the space inside the cap 141, the atmosphere of the cavity 119 has the same vacuum degree as the atmosphere inside the cap 141. have. That is, when the hollow portion 119 is isolated, the hollow portion 11
Since 9 is sealed in the atmosphere of the oxidation step shown in FIG. 5B, the cavity 119 cannot be maintained at a very high degree of vacuum. On the other hand, in the present embodiment, the degree of vacuum of the hollow portion 119 is the degree of vacuum in the cap body 140, that is, the degree of vacuum when the annular joint portion 15 of the cap body 140 is formed (for example, 10 ⁻² Pa to 10 ^{−). The} degree of vacuum is about ⁴ Pa). Therefore, the heat radiation of the infrared sensor can be suppressed, and the detection sensitivity and detection accuracy of the infrared sensor can be improved.

However, instead of removing all the wall portions as in the present embodiment, the wall portions and columns may be partially left. Even in that case, the effect of forming the annular bonding portion 15 by utilizing a metal bond or a hydrogen bond and the effect of providing a cap body for each cell region can be exhibited.

The cavity 119 shown in FIG. 5 and the space inside the cap body 140 do not have to communicate with each other.
Even in that case, the effect of forming the annular bonding portion 15 by utilizing a metal bond or a hydrogen bond and the effect of providing a cap body for each cell region can be exhibited.

-Method of Forming Cap Body- FIGS. 7A to 7F are sectional views showing a method of forming a cap body used in the electronic device of this embodiment.

First, in the step shown in FIG. 7A, a cap wafer 150 is prepared by sequentially epitaxially growing a Ge layer and a Si layer on a silicon wafer. In order to epitaxially grow a Ge layer having a thickness of about 3 μm on a silicon wafer, as described above, the Si _1-x Ge _x layer is epitaxially grown on the silicon wafer so that the Ge component ratio x changes from 0 to 1. After that, the Ge layer is epitaxially grown to a predetermined thickness. Also, after that,
After a Si _1-x Ge _x layer is epitaxially grown on the Ge layer so that the Ge component ratio x changes from 1 to 0, a Si layer having a thickness of about 1 μm is epitaxially grown. Then, on the surface of the Si layer, a Fresnel lens which is a convex lens for condensing infrared rays on each infrared sensor is formed.

Then, with the surface of the cap wafer 150 on which the Fresnel lens is formed facing downward, as shown in FIG.
As shown in (a), an Al film 151 having a thickness of about 600 nm is formed on the surface of the cap wafer 150 facing the Ge layer and the Si layer by a vapor deposition method, a sputtering method, or the like.

Next, in the step shown in FIG. 7B, the Al film 1
A resist pattern (not shown) is formed on 51, and the Al film 151 is etched using the resist pattern as a mask to form an annular film 144.

Next, in the step shown in FIG. 7C, the annular film 1
44 as a mask (hard mask), or dry etching (RIE) with the resist pattern left.
The cap wafer 150 is then formed with the cylindrical portion 142 that surrounds the concave portion that becomes the cavity of each infrared sensor. At this time, the cap wafer 150 is composed of the substrate portion 141 having the remaining portion of the silicon wafer, the Ge layer, the Si layer, the Fresnel lens, and the like, and the tubular portion 142.
The height of 2, that is, the depth of the recess is several μm or more.

As a method of forming the cap body, instead of the bulk Si substrate, an oxide insulating layer (for example, so-called BO) is used.
It is also possible to use an SOI substrate having an (X layer). In that case, since the Si substrate can be etched under the condition that the etching selection ratio between the insulating layer and the Si substrate is high, it becomes possible to reliably stop the formation of the concave portion at the insulating layer portion.

Next, in the step shown in FIG. 7D, with the substrate portion 141 of the cap wafer 150 facing upward, I
By dry etching using CP-RIE, the notch 152 for separating the substrate 141 and separately forming the cap body of each infrared sensor is formed on the substrate 141 of the cap wafer 150. And FIG. 5 (f)
And a main body substrate 100 having a structure as shown in FIG.
5F and FIG. 3 on the main body substrate 100.
An annular film 118 made of Al having the shape shown in FIG.
To form.

Next, in the step shown in FIG. 7E, the cap wafer 15 is formed on the main body wafer 100 on which the infrared sensor is formed through the steps shown in FIGS. 5A to 5E, for example.
0 is placed and the annular films 118 and 144 are joined to each other to perform a joining process by pressure bonding to form the annular joining portion 15 as shown in FIG.

Next, in the step shown in FIG. 7F, the cap wafer is divided by the notch portion 152 of the cap wafer 150 for each infrared sensor, and the main body wafer 10
By cutting 0 for each infrared sensor by dicing, a discrete infrared sensor including the Si substrate 110 and the cap body 140 (see FIG. 5F) can be obtained.

-Details of Joining Process by Pressure Bonding- FIG. 8 is a cross-sectional view schematically showing the structure of an apparatus used for pressure bonding. As shown in the figure, in the chamber 160, a supporting member 161 for applying pressure for pressure bonding,
A broadband rotary pump 162 for maintaining a vacuum inside the chamber 160 and irradiation devices 163, 164 for irradiating Ar are attached. Then, in a state where the main body wafer 100 is arranged above and the cap wafer 150 is arranged below, the irradiation devices 163 and 164 irradiate the annular films 118 and 144 (see FIG. 7D) with Ar atom beams, respectively. By this process, the annular films 118,
The contaminants and the oxide film on the Al surface constituting 144 are removed. Then, the vacuum degree in the chamber 160 is set to 10 ⁻⁴ P.
Room temperature (for example, about 30 ℃) with the level kept at a
Then, a pressure of 0.5 MPa to 20 MPa is applied to both annular membranes 11.
By applying a voltage between 8 and 144, each annular film 118,
144 are joined together.

At this time, before pressure bonding, the annular films 118,
The Ar adsorbed on the surface may be expelled by heating 144 to about 150 ° C.

Moreover, since the dangling bond can be exposed on the surface of the metal such as Al by irradiating with O atom or other neutral atom instead of irradiating with Ar atom,
The same effect as this embodiment can be obtained.

As the metal used for joining, other metals (including alloys) of Al can be used. In particular, In, Cu, Au, Ag, Al—Cu alloys having a low melting point are at room temperature or room temperature. It is possible to join at low temperature close to. As these metals, metals of the same kind may be used, or metals of different kinds may be used.

For example, if an In film is formed as a ring-shaped film by vapor deposition and pressure is applied, the surface of the In film is crushed and I
The natural oxide film existing on the surface of the n film is crushed, and In is metal-bonded. Such crimping can also be used.

Further, as the joining method, there are a method of using not only thermocompression but also ultrasonic joining, a method of giving composition deformation at room temperature and joining, and any method may be used. further,
Bonding using hydrogen bonds between Si, between Si and oxide films, between oxide films, etc. is also possible.

Particularly, by bonding at a vacuum degree of about 10 ^-2 Pa to 10 ^-4 Pa, the vacuum degree of the internal space is increased to maintain the functions of the infrared sensor and the like to some extent, while maintaining a high vacuum state. Since it is possible to avoid the difficulty for performing the bonding, it is possible to perform the bonding which is practical and suitable for mass production.

According to the present embodiment, unlike the conventional device described above, the entire cell array including many sensors and elements such as radiating elements is not held in a vacuum state, but a wafer on which many infrared sensors are formed is used. At the same time, since each infrared sensor can be individually sealed in a vacuum state,
It can be easily applied to a discrete type element.

In particular, this embodiment is a manufacturing method suitable for practical use because the manufacturing process of the electronic device, particularly the CMOS process can be used as it is.

Further, since the sealing portion is not formed by soldering as in the prior art but is formed by joining soft metals such as aluminum, the size of an element such as an infrared sensor is small. It can be easily applied to

Further, according to the manufacturing process of the present embodiment, even when a large number of discrete infrared sensors are formed on the wafer, the cap body can be bonded to each infrared sensor individually. In particular, as shown in FIG. 7D, by forming the cut portion 152 in the substrate portion 141, the stress applied to the joint portion can be made uniform for each cell, so that a large stress locally occurs during the joint. Does not work, and the reliability of the connecting portion can be improved.

(Second Embodiment) FIG. 9 shows a second embodiment of the present invention.
3 is an electric circuit diagram for explaining the configuration of the infrared area sensor according to the embodiment of FIG. The specific structure of the infrared area sensor of this embodiment is as shown in FIG.

As shown in the figure, the main body substrate is provided with a cell array in which a large number of cells A1 to E5 each having a bolometer 201 and a switching transistor 202 are arranged in a matrix. The size of one cell is, for example, 4
Although it is about 0 μm to 50 μm, it may be 20 μm or more, which is approximately twice the wavelength of infrared rays to be detected. The gate electrode of the switching transistor 202 of each cell is connected to the selection lines SEL-1 to SEL-5 extending from the vertical scanning circuit 209 (V-SCAN). One end of the bolometer 201 of each cell is connected to the power supply line 205, and the source of the switching transistor 202 is a data line 204a-extending from the ground through the reference resistors Ra-Re.
It is connected to 204e. In addition, the data line 204
a to 204e are switching transistors S, respectively.
It is connected to the output amplifier 206 via Wa to SWe. Signal lines 207a to 207e extending from the horizontal scanning circuit 208 (H-SCAN) are connected to the gate electrodes of the switching transistors SWa to SWe.

FIG. 10 is a timing chart showing the method of controlling the infrared area sensor of this embodiment. The selection line SEL-1 is controlled by the vertical scanning circuit (V-SCAN).
Is driven, the switching transistor 202 of each of the cells A1 to E1 is turned on, and the voltage passed through the reference resistors Ra to Re is supplied to the bolometer 201. On the other hand, the horizontal scanning circuit (H-SCAN) sequentially drives the switching transistors SWa to SWe to output the data Da1 to De1 of the cells A1 to E1 to the output amplifier 206.
Is output from. Next, the vertical scanning circuit (V-SCA
When the selection line SEL-2 is driven by the control of N), the switching transistors SWa to SWe are sequentially driven by the control of the horizontal scanning circuit (H-SCAN), and the data Da2 of the cells A2 to E2. De2 is output from the output amplifier 206. Similarly, the vertical scanning circuit (V-SCA
N), by the control of the horizontal scanning circuit (H-SCAN), the data Da3 to De3 of each cell A3 to E3 and each cell A4.
˜E4 data Da4 to De4 and cells A5 to E5 data Da5 to De5 are sequentially output from the output amplifier 206.

Then, the input levels of infrared rays in the cells in which the bolometers 201 are arranged are totaled, and two-dimensional information regarding the detection target is obtained.

FIGS. 11A to 11F are perspective views showing a manufacturing process of an infrared area sensor having the cell array of this embodiment.

In the steps shown in FIGS. 11A to 11E, the same processes as the steps shown in FIGS. 7A to 7E in the first embodiment are performed.

Then, in the step shown in FIG. 11F, the cap wafer 150 is divided by the notches 152 to obtain an infrared area sensor in which the cap body 140 is mounted for each cell of the cell array.

Here, in the division shown in FIG. 11 (f), the thickness of the remaining portion in the cut portion 152 may be set so as to be naturally performed at the time when the crimping force for joining is applied. Alternatively, a pressing force for splitting may be separately applied to the cut portion 152 after the joining by the above is completed.

Incidentally, in FIGS. 11A to 11F,
Since the structure of the infrared area sensor shown in FIGS. 7A to 7F is basically similar to that of the infrared area sensor shown in FIG.
Cells in discrete and integrated devices generally differ significantly in size.

An electronic device having a vacuum dome having a diameter (or one side) of several hundreds μm or less and a height of several hundreds μm or less could not be realized by the conventional technique, but according to the present embodiment. It has become possible to form such electronic devices. In this case, the wall thickness of the cylindrical portion of the cap body is several tens of μm or less, and the thickness of the ceiling portion is several hundreds of μm or less. In particular,
A vacuum dome having dimensions of several tens of μm or less in diameter (or one side) and several μm or less in depth can be called a “μ vacuum dome”. Further, the technique for forming such a vacuum dome requires joining of annular films having a thickness of submicron, and thus can be referred to as a "nano-junction μ vacuum dome".

In the case of an infrared area sensor having a cell array, the main body wafer 100 is provided with a bolometer, wirings for connecting the cells, an electric circuit, etc., but in FIGS. 11 (a) to 11 (f). Are not shown. Further, since a plurality of infrared area sensors each having a cell array are generally formed on one wafer, dicing for dividing the main body wafer 100 into each chip after the step shown in FIG. Is performed.

According to this embodiment, the following effects can be exhibited.

First, as in the conventional case, a large area including the entire cell array is covered with one cap body.
A large pressure force may be locally applied to the joint portion during the pressure bonding for joining, which may cause breakage of the joint portion or cracking of the substrate. On the other hand, when the cap body is bonded to each cell individually as in the present embodiment, as shown in FIG. 11, by providing the cut portion 152 in the cap wafer 150, each bonding is performed at the time of bonding by pressure bonding. The stress applied to the parts can be made uniform. At that time, the cap wafer may be naturally divided at the cut portion by the pressure force of bonding. That is, it is possible to prevent excessive stress from being locally generated.
It is possible to improve reliability in the subsequent steps or during actual use.

Secondly, when the entire cell array is enclosed by one cap body as in the conventional infrared sensor, if the joint failure occurs at a part of the joint portion, the entire cell array becomes defective. It is almost impossible to give relief. On the other hand, according to this embodiment, in an electronic device in which a large number of cells in which elements such as sensors are arranged are provided in an array, a cap body for vacuum sealing is attached to each cell, Even when the bonded portion of the cell is not maintained in a normal vacuum state due to defective bonding, the failure can be remedied by taking measures such as utilizing the information of the cell adjacent to the cell.

Thirdly, in the conventional structure having a large area including the entire cell array covered with one cap body, when the cell array area is particularly large or the window portion of the cap body is thin. However, the pressure difference between the outside atmosphere and the depressurized atmosphere in the cap may cause the window to bend, which may cause cracking of the window or contact between the window and the cell. On the other hand, in the present embodiment, such a problem does not occur because the cap body having a small area is provided for each cell. Therefore, it is possible to reduce the thickness of the window portion to increase the infrared ray detection sensitivity and to downsize the device.

(Third Embodiment) FIG. 12 is a sectional view showing an example of a micro vacuum transistor having a vacuum dome structure according to a third embodiment of the present invention. The micro-vacuum transistor of this embodiment is provided with a sapphire substrate 201, an n-GaN layer 202 functioning as an electron supply layer provided on the sapphire substrate 201, and an n-GaN layer 202, and has a composition substantially equal to that of the sapphire substrate 201. Al _x Ga _{1 -x} N layer 203 that functions as an electron transfer layer composed of a compositionally graded layer that changes continuously
And an AlN layer 204 provided on the Al _x Ga _1-x N layer 203 and functioning as a surface layer, a lower electrode 205 provided on the n-GaN layer 202, and provided on the AlN layer 204. A surface electrode 206 that is in Schottky contact with the AlN layer 204 and a first insulating film 207 that is formed on the AlN layer 204 and has an opening are provided. Then, A exposed on the bottom surface of the opening of the first insulating film 207
In a region from the surface of the 1N layer 204 through the side surface of the opening of the first insulating film 207 to the upper surface of the first insulating film 207,
A thin film portion 206a of the surface electrode 206 is formed. The thin film portion 206a of the surface electrode 206 is made of a thin metal (such as Cu) having a thickness of about 5 to 10 nm, and the portion of the thin film portion 206a that is in Schottky contact with the AlN layer 204 in the opening is an electron emitting portion. And the surface electrode 20
The thick film portion 206b of No. 6 is made of metal having a thickness of 100 nm or more provided on the first insulating film 207,
06b is connected to the thin film portion 206a and functions as a pad portion for connecting wiring.

Then, a cap body 208 having a cylindrical portion surrounding the vacuum dome 210 is provided on the first insulating film 207, and an upper electrode 209a for collecting electrons is provided on the inner surface of the ceiling portion of the cap body 208. Is provided with a cap body 2
An external electrode 209b is provided on the outer surface of the ceiling portion of 08, and the upper electrode 209a and the external electrode 209b are connected to each other through a through hole penetrating the ceiling portion of the cap body 210. Further, a passivation film 211 made of silicon nitride covering the surface electrode 206, an annular film 212 made of Al formed on the passivation film 211, and an annular film 213 formed at the tip of the cylindrical portion of the cap body 208 are provided. Each annular membrane 21
2, 213 are joined to each other by crimping to form an annular joint 1
5 is formed. The vacuum dome 210 has an inner diameter of about 10 μm and a reduced pressure of about 10 ⁻⁴ Pa.

In the Al _x Ga _1-x N layer 203, the Al content ratio to Ga is almost 0 at the lower end portion (x =
0), conversely, it has a graded composition with an Al content ratio of approximately 1 at the upper end.

This vacuum transistor has a surface electrode 206.
Electrons emitted according to a signal applied between the lower electrode 205 and the lower electrode 205 are accelerated in the decompressed electron transit chamber 210 and received by the upper electrode 209, and the electron transit region is evacuated. , It functions as an amplifying element or a switching element having high insulation, small internal loss, and low temperature dependence.

(Fourth Embodiment) In each of the above embodiments, the structure in which the cap body is provided for each cell region has been described, but the present invention is not limited to this embodiment.

FIG. 14 is a sectional view showing the overall structure of an infrared sensor according to the fourth embodiment of the present invention. As shown in the figure, in the present embodiment, the cap body does not cover each cell region in one cell unit, but the sensor region R
It covers multiple cell areas of the sens. The annular joint portion surrounds the plurality of cell regions. The material of the cap body, the material forming the annular joint portion, and the forming method are the same as those in the first embodiment.

FIG. 15 is a sectional view showing the overall structure of an infrared sensor according to a modification of the fourth embodiment of the present invention.
As shown in the figure, in the present embodiment, each cell region is not individually covered, but all the cell regions of the sensor region Rsens are covered. The annular joint part surrounds the entire sensor region Rsens. The material of the cap body, the material forming the annular joint portion, and the forming method are the same as those in the first embodiment.

According to the present embodiment or its modification, the annular joint is formed by the joining using the metal bond or the hydrogen bond, or the room temperature joint, unlike the one using the conventional solder. It is possible to maintain a high degree of vacuum in the space in which the elements are enclosed, and it is possible to further improve the detection sensitivity and detection accuracy of various sensors enclosed in the cap body.

(Other Embodiments) In each of the above embodiments, the case where the element held in the reduced pressure atmosphere is a bolometer or a vacuum transistor has been described, but the present invention is not limited to the embodiment. . For example,
It can be applied to thermoelectric conversion elements other than bolometers, such as PN junction diodes, and elements that detect or emit terawaves having a wavelength of 40 μm to 50 μm, and other elements that require a reduced pressure atmosphere or an inert gas atmosphere.

In each of the above-mentioned embodiments, only the cap body is provided with the concave portion which becomes the hollow portion and the closed loop-shaped tubular portion which surrounds the concave portion. Both the body and the main body substrate may have a hollow portion and a closed-loop cylindrical portion surrounding the hollow portion. Further, only the main body substrate may have a concave portion that becomes a hollow portion and a closed-loop cylindrical portion that surrounds the concave portion. In that case, the cap body may have a flat plate shape.

The shape of the cylindrical portion surrounding the cavity is as follows.
It may have a cylindrical shape or a polygonal cylindrical shape such as a square cylindrical shape. However, in order to maintain the cavity in a reduced pressure atmosphere,
It is necessary to have a closed loop annular structure.

Further, it is also possible to use a flat main body substrate having only concave portions and no cylindrical portion. In that case, the cap substrate may have a flat plate shape or may have a recess.

Further, it is also possible to use a flat cap substrate having only a concave portion and no cylindrical portion. In that case, the main body substrate may have a flat plate shape or may have a recess.

Further, in each of the above-described embodiments, it is assumed that the hollow portion sealed by the cap body is a vacuum dome. In that case, considering the easiness of joining the annular film by pressure bonding during the manufacturing process, the pressure inside the cavity is
Preferably 10 ^-2 Pa to 10 ^-4 about Pa but, 10 ^-4 Pa
Bonding in a vacuum atmosphere reaching 10 ⁻⁷ Pa below is also possible.

The present invention can also be applied to a plasma light emitting device. A depressurized atmosphere with a pressure of 133 Pa or less and a specific atmosphere containing a specific gas (for example, helium gas, argon gas, neon gas, xenon gas, krypton gas, hydrogen gas, oxygen gas, nitrogen gas, etc.) The present invention can be applied as long as it can be sealed using bonding by pressure bonding.

In the above plasma light emitting device, the cap body of the present invention may be made of a material other than a semiconductor. For example, by forming the cap body with a transparent material such as an oxide film or a nitride film, a device in which a light emitting element that emits visible light is enclosed in a reduced pressure atmosphere or the like can be obtained. When adopting that configuration, after depositing a transparent insulating film or the like on the Si substrate, Si is formed on the transparent insulating film.
A cylindrical portion surrounding the concave portion that does not reach the substrate (the outer surface may reach the Si substrate) is formed, and a cap body is formed for each cell on the main body substrate by the bonding method described in each of the above embodiments. By the procedure of sealing and further removing only the Si substrate by dry etching,
A transparent cap body can be mounted on each cell.

[0166]

According to the present invention, since the cap body for holding at least one cell region in which at least a single element is arranged in a reduced pressure atmosphere or an inert gas atmosphere is provided, a manufacturing process of an existing electronic device is performed. While utilizing the above, it is possible to provide a highly reliable electronic device suitable for both discrete and integrated structures and a method for manufacturing the same.

[Brief description of drawings]

1A to 1D are sectional views schematically showing an example of a basic structure of an electronic device of the present invention.

2A to 2D are cross-sectional views schematically showing a structural example of a bonding portion for holding a vacuum of the electronic device of the present invention.

3A and 3B are, respectively, a plan view and a cross-sectional view showing an example of an electrical connection structure suitable for an electronic device of the present invention, respectively.

4A and 4B are a cross-sectional view and an electric circuit diagram of the infrared sensor according to the first embodiment of the present invention.

5A to 5F are cross-sectional views showing a manufacturing process of the infrared sensor according to the first embodiment of the present invention.

6A to 6E are plan views showing a process of forming a bolometer and its peripheral region.

7A to 7F are cross-sectional views showing a method of forming a cap body used in the infrared sensor of the first embodiment.

FIG. 8 is a sectional view schematically showing the configuration of an apparatus used for crimping.

FIG. 9 is an electric circuit diagram for explaining a configuration of an infrared area sensor according to a second embodiment of the present invention.

FIG. 10 is a timing chart showing a method of controlling the infrared area sensor according to the second embodiment.

11A to 11F are perspective views showing a manufacturing process of the infrared area sensor having the cell array of the second embodiment.

FIG. 12 is a sectional view showing an example of a micro vacuum transistor having a vacuum dome structure according to a third embodiment of the present invention.

FIG. 13 is a sectional view showing the overall structure of an infrared sensor according to the first and second embodiments of the present invention.

FIG. 14 is a sectional view showing an overall structure of an infrared sensor according to a fourth embodiment of the present invention.

FIG. 15 is a cross-sectional view showing the entire structure of an infrared sensor according to a modified example of the fourth embodiment of the present invention.

[Explanation of symbols]

10 Main board 11 cell area 12 annular membrane 20 cap body 21 board part 22 Tube 23 Cavity 24 Ge layer 25 Si layer 26 annular membrane 27 grid pattern 30 switching transistors 31 Gate electrode 32 source electrode 33 drain electrode 35 Impurity diffusion layer 40 elements 41 Interlayer insulation film 42 passivation film 51 wiring 100 main body wafer 110 Si substrate 111 resistor 112 Silicon nitride film 113 Silicon oxide film 116 Silicon oxide film 117 passivation film 119 cavity 120 resistance element (bolometer) 130 switching transistor 131 Source area 132 drain region 133 gate electrode 140 cap body 141 board part 142 Tube 143 cavity 144 annular membrane Wafer for 150 caps 151 Al film 152 Notch

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 29/84 H01L 27/14 A 35/32 K 37/00 D 29/80 A (72) Inventor Masahiko Hashimoto Osaka 1006 Kadoma, Kadoma-shi, Matsushita Electric Industrial Co., Ltd. (72) Inventor Michio Okajima 1006 Kadoma, Kadoma-shi, Osaka Prefecture In-house (72), Matsushita Electric Industrial Co., Ltd. Shinichi Yamamoto 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Sangyo Co., Ltd. F-term (reference) 4M112 AA01 AA02 DA03 DA07 DA08 DA09 DA11 DA12 DA15 DA16 EA02 EA04 EA06 EA07 EA08 EA11 FA09 FA20 GA01 4M118 AA10 AB01 BA06 CA03 CA14 CA32 CA35 CB07 FB07 HA10 GD07 HA09 FC09 GA02 GA09 FC02 GA10 GA02 FC09 GA02 GB04 GJ10 GL04 GL16 GV08

Claims (32)

[Claims] 1. A main body substrate having a plurality of cell regions in which at least one element is arranged, a cap body mounted on the main body substrate, and at least one cell region of the plurality of cell regions. A cavity provided in a region where the element is arranged, surrounded by the main body substrate and the cap body and maintained in a reduced pressure atmosphere or an inert gas atmosphere, and provided between the main body substrate and the cap body. An electronic device comprising: an annular joint portion for blocking the cavity from an external space. 2. The electronic device according to claim 1, wherein a first annular film formed on the body substrate and surrounding the element, and a second annular film formed on the cap body. The electronic device, further comprising: the annular joint portion formed between the first and second annular films. 3. The electronic device according to claim 2, wherein the material of the first and second annular films is Al, In, Cu,
Au, Ag, Ti, W, Co, Ta, Al-Cu alloy,
An electronic device comprising a material selected from at least one of oxide films. 4. The electronic device according to claim 3, wherein the materials of the first and second annular films are the same as each other. 5. The electronic device according to claim 1, wherein the body substrate is made of a semiconductor, and the element and the external circuit on the body substrate are the body. An electronic device, wherein the electronic devices are electrically connected to each other via an impurity diffusion layer formed in the substrate across the annular junction. 6. The electronic device according to claim 1, wherein the cap body is provided with a concave portion that forms the hollow portion and a cylindrical portion that surrounds the concave portion. The electronic device, wherein the main body substrate is provided with an engaging portion that engages with the tubular portion. 7. The electronic device according to claim 1, wherein the electronic device is an element selected from an infrared sensor, a pressure sensor, an acceleration sensor and a vacuum transistor. An electronic device characterized by: 8. The electronic device according to claim 7, wherein the electronic device is an infrared sensor, and the element provided on the main body substrate is a thermoelectric conversion element. 9. The electronic device according to claim 8, wherein the cap body has a Si substrate, and a semiconductor layer provided on the Si substrate and having a bandgap smaller than 1.1 eV. Characterized electronic device. 10. The electronic device according to claim 8 or 9, wherein the uppermost layer of the cap body is formed of a Si layer on which a diffraction pattern serving as a Fresnel lens is formed. 11. The electronic device according to claim 7, wherein the electronic device includes a thermoelectric conversion element, a support member for supporting the thermoelectric conversion element, and a second member formed below the support member. An electronic device, which is an infrared detection sensor having a cavity. 12. The electronic device according to claim 11, wherein a pillar or a wall extending from the supporting member is not provided inside the second cavity. 13. The electronic device according to claim 11, wherein the second hollow portion is communicated with the hollow portion. 14. The electronic device according to claim 1, wherein a plurality of the annular joint portions are provided so as to surround the plurality of cell regions. device. 15. A body substrate having a plurality of cell regions in which at least one element is arranged and a cap substrate are prepared, and the plurality of body substrates are provided on at least one of the body substrate and the cap substrate. Step (a) of forming a plurality of recesses surrounding at least one cell region of the cell region, and applying a pressing force between the body substrate and the cap substrate, thereby forming the body substrate and the cap. A step (b) of forming an annular joint so that at least a part of the plurality of recesses remains as a cavity that is shielded from the external space between the substrate and the substrate. . 16. The method for manufacturing an electronic device according to claim 15, wherein in the step (a), a plurality of first and second annular films surrounding the recess are formed on the main body substrate and the cap substrate, respectively. In the step (b), the method for manufacturing an electronic device is characterized in that the annular joint is formed between the first and second annular films. 17. The method for manufacturing an electronic device according to claim 15, wherein the step (b) is performed by bonding using hydrogen bond or metal bond, or room temperature bonding. Manufacturing method. 18. The method of manufacturing an electronic device according to claim 16, wherein in the step (a), In, Cu, Al, Au, Ag and Ti are used as materials for the first and second annular films. , W, Co,
A method of manufacturing an electronic device, which is performed using a material selected from at least one of Ta, an Al-Cu alloy, and an oxide film. 19. The method of manufacturing an electronic device according to claim 18, wherein the same materials are used as the materials of the first and second annular films. 20. The method of manufacturing an electronic device according to claim 15, wherein the step (b) is performed without heating the main body substrate and the cap substrate to 450 ° C. or higher. And a method for manufacturing an electronic device. 21. The method of manufacturing an electronic device according to claim 15, wherein in step (a), the cap substrate is divided into a plurality of regions. A method of manufacturing an electronic device, comprising forming a slit. 22. The method of manufacturing an electronic device according to claim 16, wherein in the step (a), a recess surrounded by the second annular films is formed on the cap substrate, and a plurality of cylinders surrounding the recess. And a method for manufacturing an electronic device. 23. The method of manufacturing an electronic device according to claim 22, wherein in the step (a), an engaging portion that engages with a tubular portion of the cap substrate is formed in the main body substrate. Electronic device manufacturing method. 24. The method of manufacturing an electronic device according to claim 15, wherein the step (b) is performed in a reduced pressure atmosphere or an inert gas atmosphere. Electronic device manufacturing method. 25. The method of manufacturing an electronic device according to claim 24, wherein the step (b) is performed in a reduced pressure atmosphere having a pressure higher than 10 ⁻⁴ Pa. 26. The method of manufacturing an electronic device according to claim 15, further comprising a step of dividing the main body substrate into cells, after the step (b). And a method for manufacturing an electronic device. 27. A body substrate having a plurality of cell regions in which at least one element is arranged and a cap substrate are prepared, and the plurality of cell regions are provided on at least one of the body substrate and the cap substrate. (A) for forming a recess surrounding the substrate, and pressing force is applied between the main body substrate and the cap substrate to form a ring-shaped joint by hydrogen bonding or metal bonding or room temperature bonding. In the step (b), the annular joint is formed such that at least a part of the recess remains in the plurality of cell regions as a cavity that is shielded from an external space. And a method for manufacturing an electronic device. 28. The method of manufacturing an electronic device according to claim 27, wherein in the step (a), a first annular film surrounding a plurality of cell regions is formed on the body substrate, and the cap substrate is formed. A second ring having substantially the same pattern as that of the first annular film
A method for manufacturing an electronic device, comprising forming the annular film of 29. The method of manufacturing an electronic device according to claim 28, wherein in the step (a), In, Cu, Al, Au, Ag, Ti, W are used as materials for the first and second annular films. , Co,
A method of manufacturing an electronic device, which is performed using a material selected from at least one of Ta, an Al-Cu alloy, and an oxide film. 30. The method of manufacturing an electronic device according to claim 29, wherein the same material is used as the material of the first and second annular films. 31. The method of manufacturing an electronic device according to claim 27, wherein the step (b) is performed without heating the main body substrate and the cap substrate to 450 ° C. or higher. And a method for manufacturing an electronic device. 32. The method of manufacturing an electronic device according to claim 27, wherein the step (a) is arranged in one electronic device by the first and second annular films. And a method for manufacturing an electronic device, which is performed so as to surround all of the cell regions to be processed.