JP6773089B2 - device - Google Patents

Description

The present invention also relates to the device.

MEMS (Micro-Electro Mechanical Systems) devices manufactured using semiconductor technology and having both electrical circuit elements and fine mechanical elements are currently used in acceleration sensors, printer heads, pressure sensors, DMDs (Digital Micromirror Devices), etc. The market size is expanding.

Usually, a MEMS device has a movable part (functional element) formed in a hollow shape. Since the movable part is required to be protected from the outside air or the like, it is sealed with a vacuum (or a constant atmospheric pressure). Insufficient vacuum encapsulation causes a decrease in reliability such as malfunction of the MEMS device.

Examples of the sealing method used for MEMS devices include anodic bonding in which a silicon substrate and a glass substrate to which a high voltage is applied are bonded at a temperature of 300 ° C to 500 ° C. In the anode bonding, since the device substrate and the package substrate are directly bonded, a space (Cavity) for sealing the moving part is required separately.

There is also a method of using an airtight package substrate sealed in a high vacuum in the mounting process.

It has also been proposed to join the device substrate and the package substrate and collectively seal them in the wafer process (wafer level) for manufacturing the MEMS device. For example, in Patent Document 1, a metal layer of the same material is formed in a sealing portion for vacuum sealing and an electrical contact portion for electrical connection, and a cover substrate and an integrated circuit board are formed at the wafer level. It is joined.

In Patent Document 2, the LTCC substrate and the MEMS substrate are bonded by anode bonding. The LTCC substrate and the MEMS substrate are electrically connected via a porous metal.

In Patent Document 3, before dicing the wafer to individual chips, the semiconductor substrate wafer on which the accelerometer is formed and the cap wafer are bonded by frit glass.

Furthermore, in recent years, by superimposing a substrate on which various elements are formed on a device in which a device substrate on which semiconductor functional elements such as various sensors and optical scanners are formed and a package substrate are formed, a compact and highly functional device The development of technology to realize this is in progress.

When joining the substrate (device substrate) on which the functional element is formed and the package substrate, the functional element is precisely vacuum-sealed and the electrical connection between the electrodes formed on each substrate is reliable. Is preferable.

Further, the cost of joining is preferably low.

However, the airtight package substrate conventionally used has a problem that packaging is costly.

In Patent Document 1, since the metal layer of the same material is used for the sealing portion and the electrical contact portion, the optimum material for vacuum encapsulation and the optimum material for electrical connection cannot be selected and joined. Is unreliable. Furthermore, metal layers such as Au and Ag are expensive.

In Patent Document 2, since the anodic junction having a high applied voltage and high processing temperature is used, there is a concern that the MEMS device may be adversely affected. Further, in anode bonding, a Cavity for accommodating functional elements is required separately, so that bonding on a flat substrate is difficult. Furthermore, the reliability of joining is still low because problems such as positioning accuracy of Cavity occur.

The present invention has been made in view of the above problems, and an object of the present invention is to perform inexpensive and highly reliable bonding.

In order to achieve the above object, the device according to the embodiment of the present invention has a first substrate on which an optical element is formed and a second substrate on which an optical sensor through which light transmitted through the optical element is incident is formed. And a holding portion that joins the first substrate and the second substrate to each other and holds the first substrate and the second substrate at a predetermined interval, and the holding portion is a glass frit material. It is made of a polymer resin or a noble metal, and the optical element of the first substrate is made of Si.

According to the embodiment of the present invention, inexpensive and highly reliable joining can be performed.

It is sectional drawing which shows an example of the structure of the device which concerns on Embodiment 1. FIG. It is sectional drawing which shows an example of the structure of the device which concerns on Embodiment 1. FIG. It is sectional drawing and the plane transmission view which show an example of the structure of the device which concerns on Embodiment 1. FIG. It is sectional drawing which shows an example of the structure of the device which concerns on Embodiment 1. FIG. It is a figure which shows an example of the manufacturing method of the device which concerns on Embodiment 1. FIG. It is sectional drawing which shows an example of the structure of the device which concerns on Embodiment 2. FIG. It is sectional drawing which shows an example of the structure of the device which concerns on Embodiment 2. FIG. It is sectional drawing which shows an example of the structure of the device which concerns on Embodiment 2. FIG. It is sectional drawing which shows an example of the structure of the device which concerns on Embodiment 2. FIG. It is a figure which shows an example of the manufacturing method of the device which concerns on Embodiment 2. It is a figure which shows an example of the manufacturing method of the device which concerns on Embodiment 2. It is a figure which shows an example of the manufacturing method of the device which concerns on Embodiment 2. It is a figure which shows an example of the manufacturing method of the device which concerns on Embodiment 2. It is a figure which shows an example of the manufacturing method of the device which concerns on Embodiment 2. It is a figure which shows an example of the manufacturing method of the device which concerns on Embodiment 2. It is sectional drawing and the plane transmission view which show an example of the structure of the device which concerns on Embodiment 2. FIG.

<First Embodiment>
(Device structure)
FIG. 1 is an example of a cross-sectional view showing the structure of the device 100 according to the present embodiment.

As shown in FIG. 1, a functional element (for example, a sensor, an IC circuit, etc.) 4, an electrode 5, and a thin film metal pad 7 are formed on the first substrate 1. The electrode 5 and the thin film metal pad 7 are laminated and formed.

A through electrode 6 is formed on the second substrate 2, a thin film metal pad 8 is formed at one end of the through electrode 6, and a thin film metal pad 9 is formed at the other end of the through electrode 6. It is formed. Further, the plating layer 10 is formed by laminating with the thin film metal pad 9.

The bonding material 11 is formed between the first substrate 1 and the second substrate 2.

The conductive material 12 is formed between the thin film metal pad 7 and the thin film metal pad 8.

The bonding material 11 joins the first substrate 1 and the second substrate 2, forms a space (Cavity) 3 between the functional element 4 and the second substrate 2, and further vacuum-seals the functional element 4. It has a function to stop.

The conductive material 12 has a function of electrically connecting the first substrate 1 (device substrate) and the second substrate 2 (package substrate). Specifically, a conductive material 12 is interposed between the thin film metal pad 7 electrically connected to the functional element 4 and the thin film metal pad 8 electrically connected to the through electrode 6. Electrically connect. As a result, the functional element 4 and the through electrode 6 in the package substrate are electrically connected.

The conductive material 12 and the bonding material 11 are made of different materials. A hard and low-conductivity bonding material 11 is used for bonding in a part where strength and vacuum are required, and a soft and easy-to-process conductive material 12 is used in a part where conductivity is required. It is preferable to make a target connection.

As the bonding material 11, it is preferable to use a material having a high bonding force. By using a material having a high bonding force, the first substrate 1 and the second substrate 2 can be reliably vacuum-sealed.

Further, as the bonding material 11, it is preferable to use a material having a hardness capable of maintaining a predetermined distance between the first substrate 1 and the second substrate 2. By maintaining a predetermined distance between the first substrate 1 and the second substrate 2, Cavity 3 for vacuum-sealing the functional element 4 can be formed. As a result, it is not necessary to separately form a space for accommodating the functional element 4 on the package substrate. Further, the first substrate 1 and the second substrate 2 can be joined as a flat plate.

Further, as the bonding material 11, it is preferable to use a material that is resistant to mechanical stress. By using a material having mechanical stress resistance, it is possible to make it difficult to receive mechanical damage due to dicing (chip division) when forming a chip after joining a silicon wafer having a large diameter.

Moreover, it is preferable to use an inexpensive material as the bonding material 11. By using an inexpensive material, the overall cost of joining can be reduced even if the joining area is expanded.

Specifically, as the bonding material 11, it is preferable to use a glass frit material, a polymer resin, or the like. Examples of the polymer resin include epoxy, dry film, BCB, polyimide, UV curable resin and the like. However, the polymer resin has problems that the heat resistant temperature is not high and the airtightness is not high.

It is also possible to use a precious metal typified by Au or the like as the bonding material 11 as the bonding material. However, when a large amount of expensive precious metal is used as a bonding material, it is difficult to control the cost, which is not preferable.

The conductive material 12 is preferably a material having high conductivity, softness, and easily crushed by pressurization and heating at the time of joining. Further, it is preferable that the material can withstand the temperature at the time of solder reflow such as solder joining.

Specifically, as the conductive material 12, it is preferable to use a metal such as Au, Ag, a paste material of an alloy thereof, a solder material, or the like. By heating and pressurizing the conductive material 12 using these materials, mutual diffusion of the metal material occurs between the conductive material 12 and the thin film metal pad 7 and between the conductive material 12 and the thin film metal pad 8. , Diffusion bonding can be performed. As a result, the functional element 4 and the through electrode 6 in the package substrate can be electrically connected.

In addition, in this specification, "diffusion bonding" means that the conductive material 12 is heated and pressurized, and the through electrode 6 and the conductive material 12 are electrically connected by utilizing the diffusion of the metal material. And.

The first substrate 1 is a substrate on which a functional element 4 having a movable portion, a detection portion, and the like, and other electronic circuits and the like are formed. On the first substrate 1, there are various films and patterns for forming functional elements, electronic circuits, and the like. It is preferable to use silicon as the first substrate 1. When silicon is used, the silicon substrate may be a Bulk substrate or an SOI (Silicon On Insulator) substrate.

The second substrate 2 is a package substrate for vacuum-sealing (or sealing in a space adjusted to have a pressure lower than atmospheric pressure) the functional element 4 housed in the sealed Cavity 3. As the second substrate 2, ceramic, glass, silicon or the like can be used.

The electrode 5 is electrically connected to the functional element 4. As the electrode 5, aluminum, an aluminum alloy, or the like can be used.

The through electrode 6 is formed in the second substrate 2. By forming the thin film metal pad 8 and the thin film metal pad 9 on both exposed ends, it has a function of electrically connecting to an external circuit or electrically connecting to a functional element 4. As the through electrode 6, metals such as Au, Ag, Ti, W, etc., alloys thereof, low-resistance polysilicon, and the like can be used.

The thin film metal pad 7 electrically connects the electrode 5 and the conductive material 12. The thin film metal pad 7 functions as a pad for improving the adhesion between the electrode 5, the thin film metal pad 7, and the thin film metal pad 7 and the conductive material 12. Further, the thin film metal pad 7 functions as a barrier layer for preventing the metal material from diffusing.

Since it has a plurality of functions, the thin film metal pad 7 is preferably formed in a laminated structure.

It is preferable to use a metal such as Cr or Ti, an alloy thereof, or the like for the boundary (for example, the first layer) with the electrode 5 in which the improvement of adhesion is emphasized. Further, it is preferable to use a metal such as Pt or Ni, an alloy thereof, or the like for the barrier layer (for example, the second layer) in which the diffusion prevention of the metal material is emphasized. Further, it is preferable to use a metal such as Au, Ag, Cu, an alloy thereof, or the like for the boundary (for example, the third layer) with the conductive material 12 in which the improvement of adhesion is emphasized.

The thin film metal pad 8 electrically connects the conductive material 12 and the through electrode 6. Similar to the thin film metal pad 7, the thin film metal pad 8 functions as a pad for improving the adhesion between the conductive material 12 and the thin film metal pad 8, and the thin film metal pad 8 and the through electrode 6. Further, the thin film metal pad 8 functions as a barrier layer for preventing the metal material from diffusing. Therefore, it is preferable that the thin film metal pad 8 is also formed in a laminated structure like the thin film metal pad 7.

As the thin film metal pad 8, the same material as the thin film metal pad 7 can be used.

The thin film metal pad 9 functions as a UBM (Under Barrier Metal) layer for the plating layer 10. By using the UBM layer, the growth of the intermetallic compound layer formed at the interface between the plating layer 10 and the penetrating electrode 6 is suppressed, and the plating layer 10 and the thin film metal pad 9 and the thin film metal pad 9 and the penetrating electrode 6 are suppressed. It is possible to improve the interface strength with 6.

As the thin film metal pad 9, Ti, Cr, Ni, Al or the like can be used.

The plating layer 10 is a layer required when the device 100 according to the present embodiment is finally solder-mounted on the printed circuit board. As the plating layer 10, Ni, Au, Ag, Cu or the like can be used.

According to the device 100 according to the present embodiment, by using an inexpensive and hard material as the bonding material 11 and a soft and highly conductive material as the conductive material 12, the functional element 4 is vacuum-sealed and the functional element is sealed. The optimum material can be selected for each bonding of 4 and the electrical connection between the package substrate. In addition, vacuum sealing and electrical connection can be performed simultaneously at the wafer level. Therefore, inexpensive and highly reliable joining can be performed.

(Modification example 1)
FIG. 2 is an example of a cross-sectional view showing the structure of the device 101 according to the present embodiment. The part different from the device 100 shown in FIG. 1 will be mainly described. The same parts as the device 100 are given the same reference numerals.

The difference between FIGS. 1 and 2 is that the material used as the package substrate (second substrate 13) is LTCC (Low Temperature Co-fired Ceramic) instead of ceramic, glass, silicon, or the like. That is the part.

By using the LTCC substrate as the second substrate 13, it becomes easy to freely control the shape and position of the internal wiring 16 formed in the LTCC substrate. Therefore, the positions of the metal thin film pad 9 and the conductive material 12 are determined when the internal wiring 16 is formed on the package substrate as compared with the case where the through electrode 6 as shown in the device 100 is formed on the package substrate. Even if the design is relatively free, the metal thin film pad 9 and the conductive material 12 can be reliably electrically connected. That is, even if the thin film metal pad 9 and the conductive material 12 do not exist on the same straight line in the vertical direction, the thin film metal pad 9 and the conductive material 12 can be electrically connected by devising the pattern shape of the internal wiring 16. Can be connected.

(Modification 2)
FIG. 3A is an example of a cross-sectional view showing the structure of the device 102 according to the present embodiment. Further, FIG. 3B is an example of a plane transmission diagram showing the structure of the device 102 according to the present embodiment.

The part different from the device 100 shown in FIG. 1 will be mainly described. The same parts as the device 100 are given the same reference numerals.

In the device 100 shown in FIG. 1, the electrode 5, the thin film metal pad 9, and the conductive material 12 are present on the same straight line in the vertical direction. These alignments had to be done for electrical connections, and there were layout restrictions during the design.

In the device 102 shown in FIG. 3A, the electrode 5, the thin film metal pad 9, and the conductive material 12 do not exist on the same straight line in the vertical direction. That is, as shown in FIG. 3B, the positions of the electrode 5, the thin film metal pad 9, and the conductive material 12 are all displaced.

Even in such a case, the structure of the device 102 makes it possible to electrically connect the electrode 5, the thin film metal pad 9, and the conductive material 12.

For example, the electrode 5 and the conductive material 12 are electrically connected by using the thin film metal pad 7. Further, for example, the conductive material 12 and the through electrode 6 are electrically connected by using the thin film metal pad 8.

That is, as shown in FIG. 3A, the thin film metal pad 7 and the thin film metal pad 8 can be used as internal wiring, the thin film metal pad 7 can be extended, and the electrode 5 and the conductive material 12 can be electrically connected. As described above, the thin film metal pad 7 is formed. Further, the thin film metal pad 8 is extended to form the thin film metal pad 8 so that the conductive material 12 and the through electrode 6 can be electrically connected to each other. By devising the pattern shapes of the thin film metal pad 7 and the thin film metal pad 8 in this way, even if the electrodes 5, the thin film metal pad 9, and the conductive material 12 are all displaced in the vertical direction, the electrode 5 and the thin film are thin. The metal pad 9 and the conductive material 12 can be electrically connected.

The device 102 shown in FIG. 3 has a higher degree of freedom in layout. Since the positions of the electrode 5, the thin film metal pad 9, and the conductive material 12 can be freely selected and designed, it is easy to put into practical use.

Further, although the device 102 has the through electrode 6 on the package substrate, it has the same effect as the internal wiring 16 of the LTCC substrate 13 and the wafer level CSP (Wafer level Chip Size Package). Therefore, it is possible to achieve high integration and miniaturization of the device.

(Modification 3)
FIG. 4 is an example of a cross-sectional view showing the structure of the device 103 (semiconductor device) according to the present embodiment. The part different from the device 100 shown in FIG. 1 will be mainly described. The same parts as the device 100 are given the same reference numerals.

The difference between FIGS. 1 and 4 is that a third substrate 14 is formed on the first substrate 1. According to the device 103 according to the present embodiment, the first substrate 1 and the second substrate 2 are connected to each other via the bonding material 11, and the first substrate 1 and the third substrate 14 are connected to the bonding material 15. Can be joined at the same time through.

The joining material 11 and the joining material 15 can be made of the same material.

A lens or the like can be formed on the third substrate 14. In addition, in response to the expected expansion of MEMS device applications in the future, the third substrate 14 is used not only for integrated circuits such as IC (Integrated Circuit) circuits and LSI (Large Scale IC) circuits, but also for optical circuits. All kinds of elements such as communication devices, mobile communication devices, and acceleration sensors for automobile airbags can be formed.

Although FIG. 4 shows an example in which three substrates are laminated and joined at the same time, the number of substrates to be laminated is not particularly limited. As shown in device 103, the substrates are three-dimensionally laminated to form a laminated structure, and these substrates are simultaneously bonded using a bonding material made of the same material, thereby significantly increasing the process for manufacturing the device. It can be expected to reduce the size of the device and reduce the size of the device.

(How to make a device)
FIG. 5 is a diagram showing an example of a method for manufacturing the device 100 according to the present embodiment. Hereinafter, a method of manufacturing the device 100 will be described with reference to FIG.

First, as shown in FIG. 5 (A), a functional element 4 such as an IC circuit or a sensor is formed on a first substrate (for example, a silicon substrate) 1 in the same manner as in the process of manufacturing a general MEMS. To.

Next, the electrode 5 is formed by a sputtering method or the like. The electrode 5 is formed of aluminum or an aluminum alloy with a film thickness of about 0.5um to 3.0um.

A thin film metal pad 7 is formed on the electrode 5 by a sputtering method or the like. The thin film metal pad 7 is formed to have a width equal to that of the electrode 5 or a size equal to or larger than that of the electrode 5. Further, the thin film metal pad 7 has a three-layer laminated structure and is formed with a film thickness of about 100 nm to 5000 nm.

Specifically, as the first layer, a Ti layer, a Cr layer, etc., and an alloy layer thereof are formed. The first layer can function as an adhesion layer. A Ni layer, a Pt layer, etc., and an alloy layer thereof are formed on the upper part of the first layer as a second layer. The second layer can function as a barrier layer for preventing the diffusion of the metal material. An Au layer, an Ag layer, a Cu layer, etc., and an alloy layer thereof are formed on the upper part of the second layer as a third layer. The third layer can function as an alloy layer for alloying with the upper layer (here, the conductive material 12).

In this embodiment, an example in which the thin film metal pad 7 has a three-layer laminated structure will be described, but the structure is not limited to this. It may have a laminated structure other than three layers.

Next, as shown in FIG. 5B, the conductive material 12 is formed on the thin film metal pad 7.

The conductive material 12 is formed to electrically connect the electrode 5 and the through electrode 6 at the time of joining in the next step. The conductive material 12 is patterned by a method such as screen printing using a noble metal such as Au or Ag, or a paste material or solder material of an alloy thereof. Since the film thickness of the conductive material 12 depends on the distance between the spaces (Cavity) 3, the so-called distance between the first substrate 1 and the second substrate 2, the film thickness is formed to be about 10 um to 50 um.

The conductive material 12 is formed of a relatively soft material (for example, a paste material) or a highly conductive material. Further, it is preferably formed of a firing material having a firing temperature of 400 ° C. to 450 ° C. or lower.

Next, after the conductive material 12 is patterned, the conductive material 12 (paste material) is prebaked in order to remove unnecessary solvents. The temperature at the time of prebaking is preferably a temperature at which gas and water in the paste material can be removed. By removing unnecessary solvent by pre-baking and further removing unnecessary gas and water, more reliable joining can be realized at the time of joining in the next step. Further, the temperature at the time of prebaking is preferably a temperature lower than the joining temperature at the joining in the next step. Therefore, it is preferable to perform prebaking at a temperature of about 200 ° C. to 400 ° C.

Next, as shown in FIG. 5C, the through electrode 6 is formed on the second substrate (for example, a glass substrate). A thin film metal pad 8 is formed at one end of the exposed through electrode 6. Further, a thin film metal pad 9 is formed at the other end of the exposed through electrode 6.

The thin film metal pad 8 is formed by using the same material as the thin film metal pad 7. For example, a three-layer laminated structure (Ti layer, Cr layer, etc., their alloy layer / Ni layer, Pt layer, etc., their alloy layer / Au layer, Ag layer, Cu layer, etc., and their alloy layer). It is formed with a film thickness of about 100 nm to 5000 nm.

The thin film metal pad 9 is formed with a film thickness of about 100 num to 10 um using Ti, Cr, Ni, Al and the like.

Next, as shown in FIG. 5 (D), the bonding material 11 is formed on the second substrate 2. The joining material 11 is formed to join the first substrate and the second substrate 2 at the time of joining in the next step.

The bonding material 11 is patterned by a method such as screen printing using a glass frit material or a polymer resin. Since the film thickness of the bonding material 11 determines the interval of Cavity 3, the bonding material 11 is formed with a film thickness of about 10um to 50um. In addition, in order to make the height of the bonding material 11 uniform, for example, a glass bead material or the like may be added to the glass frit material.

The bonding material 11 is preferably formed of a relatively hard material or an inexpensive material.

Further, in order to prevent the functional element 4 from being adversely affected by the high temperature, it is preferably formed of a firing material having a firing temperature of 400 ° C. to 450 ° C. or lower. Specifically, it is preferable to use a glass frit material or the like.

Since the firing temperature of the bonding material 11 and the firing temperature of the conductive material 12 are almost the same, the bonding for vacuum sealing between the first substrate 1 and the second substrate 2 and the first substrate 1 The bonding for electrical connection with the second substrate 2 can be performed at the same time.

Next, after the bonding material 11 is patterned, the bonding material 11 is prebaked in order to remove unnecessary solvent. It is preferable to perform prebaking at a temperature of about 200 ° C to 400 ° C.

Next, as shown in FIG. 5 (E), the device substrate manufactured in FIG. 5 (B) and the package substrate manufactured in FIG. 5 (D) are joined.

The joining machine 16 pressurizes the first substrate 1 and the second substrate 2, and further heats the first substrate 1 and the second substrate 2. The heating temperature at the time of joining is preferably about 350 ° C. to 450 ° C. That is, it is preferable that the temperature is such that the functional element 4 is not adversely affected and the bonding material 11 (for example, glass frit material) and the conductive material 12 (for example, Ag paste material) are fired and cured.

The degree of vacuum in Cavity 3 is adjusted inside the joining machine 16. As described above, the bonding material 11 and the conductive material 12 are prebaked to remove unnecessary solvents, gases, and water. Pre-baking is an important step for performing highly accurate vacuum sealing, and unnecessary gas and air are almost removed from Cavity 3 by the pre-baking and vacuuming during joining by the joining machine 16. In this state, by adjusting the degree of vacuum in Cavity 3 with the joining machine 16, high-precision joining can be performed.

As shown in FIG. 5 (F), after joining, the conductive material 12 is crushed by heating and pressurizing by the joining machine 16, and is diffusion-bonded to the thin film metal pads 7 and 8, thereby forming the conductive material 12 and the thin film metal pad. It is electrically connected to 7 and 8.

Further, as shown in FIG. 5 (F), since the bonding material 11 is made of a material that is harder than the conductive material 12, it is almost impossible to be deformed by heating or pressurizing by the bonding machine 16 after bonding. You can think that there is no such thing. That is, a predetermined distance is maintained between the first substrate 1 and the second substrate 2 by the amount of the film thickness of the bonding material 11, and Cavity 3 is formed. The functional element 4 is vacuum-sealed in Cavity 3 without forming a separate space on the package substrate.

According to the above-mentioned joining step, since the first substrate 1 and the second substrate 2 may be flat plates, unnecessary steps such as separately forming a space for accommodating the functional element 4 can be omitted. ..

Finally, the plating layer 10 is formed so as to be in contact with the thin film metal pad 9. The plating layer 10 is formed with a film thickness of about 100 nm to 100 um using Ni, Au, Ag, Cu, or the like.

According to the manufacturing method according to the present embodiment, the first substrate 1 and the second substrate 2 are bonded to each other by using the bonding material 11 which is harder than the conductive material 12 and has low conductivity. A predetermined distance can be stably maintained between the substrate 1 and the second substrate 2, and the functional element 4 can be vacuum-sealed with high accuracy. At the same time, the electrode formed on the first substrate 1 and the through electrode formed on the second substrate 2 are surely secured by diffusion bonding using the conductive material 12 which is soft and has high conductivity. Can be electrically connected to.

Further, by forming the joining material 11 with an inexpensive material, it is possible to join at low cost.

That is, according to the device according to the present embodiment and the method for manufacturing the device, the optimum material for electrical connection and the optimum material for vacuum sealing are selected, and the materials are simultaneously bonded at the wafer level. It is possible to perform inexpensive and highly reliable bonding.

<Second embodiment>
(Device structure)
FIG. 6 is an example of a cross-sectional view showing the structure of the device 200 according to the present embodiment.

The device 200 includes a first substrate 201, a second substrate 202, a third substrate 203, a functional element 204, a drive circuit 205, a thin film metal pad 206, a thin film metal pad 207, a thin film metal pad 208, a through electrode 209, and a conductive device. The material 210, the first bonding material 211, the second bonding material 212, the optical element 213, and the cavity (space) 214 are included.

A functional element 204 and a drive circuit 205 for driving the functional element 204 are formed on the first substrate 201. The functional element 204 (for example, an optical sensor, a pressure sensor, an infrared sensor, an acceleration sensor, etc.) is formed by using a known microfabrication technique and a thin film forming technique. The functional element 204 may include an actuator such as an oscillator, for example, in addition to various sensors and the like. The drive circuit 205 is formed using known semiconductor technology.

Examples of the material of the first substrate 201 include Si, SOI (silicon on insulator) and the like.

A through electrode 209 is formed on the second substrate 202, and a thin film metal pad 207 is formed at one end of the through electrode 209, and a thin film metal pad 208 is formed at the other end of the through electrode 209. It is formed. The functional element 204 is electrically connected to the outside via the through electrode 209.

The material of the second substrate 202 is not particularly limited as long as it is a material having an insulating property, and examples thereof include glass and ceramics.

An optical element 213 is formed on the third substrate 203. The optical element 213 is formed by using a known thin film forming technique. Examples of the optical element 213 include a diffraction grating, a lens, a filter, and the like.

Examples of the material of the third substrate 203 include Si and the like.

The conductive material 210 is formed between the drive circuit 205 and the through electrode 209. The drive circuit 205 and the through electrode 209 are electrically connected to each other via the conductive material 210 and the thin film metal pads 206 and 207. A thin film metal pad 206 is formed on one end of the conductive material 210, and a thin film metal pad 207 is formed on the other end of the conductive material 210.

The material of the conductive material 210 is preferably a material having high conductivity, softness, and easily crushed by pressurization and heating at the time of joining. Further, it is preferable that the material can withstand the temperature at the time of solder reflow such as solder joining. As the material of the conductive material 210, for example, metals such as Au, Ag, Al, paste materials and solder materials of alloys thereof, porous Au and the like can be used.

The thin film metal pad 206 can have a three-layer laminated structure. For example, when the thin film metal pad 206 has a laminated structure of Cr / Pt / Au, the Au layer is formed on the surface in contact with the conductive material 210 in order to increase the conductivity, and the Cr layer is the electrode of the drive circuit 205. It is preferably formed on the surface in contact with.

Similarly, the thin film metal pad 207 can have a three-layer laminated structure. For example, when the thin film metal pad 207 has a laminated structure of Cr / Pt / Au, the Au layer is formed on the surface in contact with the conductive material 210 in order to enhance the conductivity, and the Cr layer is for enhancing the adhesion. In addition, it is preferably formed on the surface in contact with the third substrate 203, and the Pt layer is preferably formed in the central layer in order to prevent diffusion. It is possible to use a Ti layer instead of the Cr layer, and it is also possible to use a Ni layer instead of the Pt layer.

Similarly, the thin film metal pad 208 can have a three-layer laminated structure. The Au layer is formed on the surface in contact with the outside, the Cr layer is formed on the surface in contact with the third substrate 203 in order to enhance the adhesion, and the Pt layer is formed in the central layer to prevent diffusion. It is preferable to be done.

The first bonding material 211 is formed between the first substrate 201 and the second substrate 202, and joins the first substrate 201 and the second substrate 202. The first substrate 201 and the second substrate 202 are joined to each other with a predetermined interval via the first bonding material 211, whereby the functional element 204 is vacuum-sealed. Between the first substrate 201 and the second substrate 202, there is a cavity 214 for packaging the functional element 204.

As the material of the first bonding material 211, it is preferable to use a glass frit material, a polymer resin, or the like.

The thickness of the first joining material 211 is preferably about 20 μm. By making the thickness of the first bonding material 211 thicker than the thickness of the functional element 204 (about 10 μm), it is possible to avoid interference between the functional element 204 and the second substrate 202 after bonding. ..

The width of the first joining material 211 is preferably about 150 μm. The width of the first bonding material 211 needs to be appropriately adjusted so that the distance between the functional element 204 and the first bonding material 211 is at least 50 μm or more.

The second bonding material 212 is formed between the first substrate 201 and the third substrate 203, and joins the first substrate 201 and the third substrate 203. The first substrate 201 and the third substrate 203 are joined to each other with a predetermined interval via the second bonding material 211. The interval can be arbitrarily adjusted by changing the thickness of the second bonding material 211.

The thickness of the second joining material 212 may be equal to the thickness of the first joining material 211. Further, the width of the second joining material 212 may be equal to the width of the first joining material 211. Further, the material of the second joining material 212 may be the same as the material of the first joining material 211.

By forming the second bonding material 212 with the same thickness, the same width, and the same material as the first bonding material 211, the device 200 can be manufactured by a low cost and a simple process. Further, by superimposing the third substrate 203 on which the optical element 213 is formed on the first substrate 201 on which the functional element 204 is formed, a compact and highly functional multilayer substrate structure is formed at low cost. The device 200 having the above can be realized.

(Modification example 1)
FIG. 7 is an example of a cross-sectional view showing the structure of the device 300 according to the present embodiment. The part different from the device 200 shown in FIG. 6 will be mainly described. The same parts as the device 200 are designated by the same reference numerals.

The device 300 includes a second bonding material 312 that is different from the device 200. The second bonding material 312 is different in thickness and width from the first bonding material 211, but the materials are the same.

As shown in FIG. 7, the thickness of the second bonding material 312 can be made thinner than the thickness of the first bonding material 211, for example, about 10 μm. Further, the width of the second bonding material 312 can be made wider than the width of the first bonding material 211, for example, about 200 μm.

By making the thickness of the second bonding material 312 thinner than the thickness of the first bonding material 211 in this way, the distance between the optical element 213 and the functional element 204 can be shortened. Therefore, since the alignment accuracy of the optical element 213 with respect to the functional element 204 can be improved, the optical characteristics of the functional element 204 can be improved.

Further, by making the width of the second bonding material 312 wider than the width of the first bonding material 211, when the wafer on which a plurality of devices are formed is divided and individualized, the division position is adjusted. Becomes easier. Therefore, since dicing with high accuracy can be performed, the device 300 can be relatively easily miniaturized.

(Modification 2)
FIG. 8 is an example of a cross-sectional view showing the structure of the device 400 according to the present embodiment. The part different from the device 200 shown in FIG. 6 will be mainly described. The same parts as the device 200 are designated by the same reference numerals.

The device 400 includes a second bonding material 412 that is different from the device 200. The second bonding material 412 is different in thickness, width, and material from the first bonding material 211.

As shown in FIG. 8, the thickness of the second bonding material 412 can be made thinner than the thickness of the first bonding material 211, for example, about 1 μm. Further, the width of the second bonding material 412 can be made wider than the width of the first bonding material 211, for example, about 200 μm. Further, the second bonding material 412 can be made of a metal, for example, an alloy of Au and Sn.

By forming the second bonding material 412 with metal in this way, it is possible to suppress the generation of gas. Therefore, the bonding temperature of the second bonding material 412 at the time of bonding is set to the first bonding material 211. It can be made lower than the bonding temperature of. Since it is possible to perform airtight sealing with a high degree of vacuum while joining at a relatively low temperature, the performance of the device 400 can be maintained even if the manufacturing process is simplified.

(Modification 3)
FIG. 9 is an example of a cross-sectional view showing the structure of the device 500 according to the present embodiment. The part different from the device 200 shown in FIG. 6 will be mainly described. The same parts as those of the device 200 are designated by the same reference numerals.

The device 500 includes a second bonding material 512 that is different from the device 200. The width and material of the second joining material 512 are different from those of the first joining material 211, but the thickness is the same.

As shown in FIG. 7, the width of the second bonding material 312 can be made wider than the width of the first bonding material 211, for example, about 200 μm. Further, the second bonding material 412 can be a polymer resin, for example, a polyimide resin.

By forming the second bonding material 512 with the polyimide resin in this way, the bonding temperature of the second bonding material 412 at the time of bonding can be set to 300 ° C. or lower. That is, since low-temperature bonding becomes possible, the material selectivity of the third substrate 203 and the functional element 204 can be expanded. For example, since it is possible to use an organic material as the material of the third substrate 203 and the functional element 204, the material cost of the device 500 can be suppressed.

According to the devices 200, 300, 400, and 500 according to the present embodiment, the thickness, width, material, and the like of the first bonding material 211 and the second bonding material 412 are appropriately changed according to various conditions. Thereby, each substrate can be bonded by using the optimum bonding material for each substrate. Therefore, inexpensive and highly reliable joining can be performed. Further, since the first bonding material and the second bonding material have both functions of substrate bonding and packaging of functional elements, it is possible to realize a compact and highly functional device while simplifying the manufacturing process.

(How to make a device)
FIG. 10 is a diagram showing an example of a method for manufacturing the device 200 according to the present embodiment. Hereinafter, a method of manufacturing the device 200 will be described with reference to FIG.

First, as shown in FIG. 10A, a functional element 204 and a drive circuit 205 are formed on a first substrate (for example, a silicon substrate) 201 by a known microfabrication technique and a semiconductor thin film forming technique.

Next, the thin film metal pad 206 is formed in contact with the drive circuit 205 by a sputtering method or the like. An electrode (for example, Al) is formed in the drive circuit 205, and the thin film metal pad 206 is formed to conduct the electrode and the conductive material 210 to be formed later. The thin film metal pad 206 has, for example, a three-layer laminated structure (for example, Cr / Pt / Au) and is formed with a film thickness of about 100 nm to 5000 nm.

Next, as shown in FIG. 10B, a dot-shaped conductive material 210 (for example, Ag paste) is formed in contact with the thin film metal pad 206 by a screen printing method or the like. When Ag paste is used as the material of the conductive material 210, it is preferable that the conductive material 210 is sufficiently heat-treated and fired at a temperature of about 200 ° C. in order to remove the solvent and the binder.

The dot diameter of the conductive material 210 is preferably about 150 μm, and is preferably smaller than the thin film metal pad 206 and the thin film metal pad 207.

The film thickness of the conductive material 210 after being heat-treated and fired is preferably about 20 μm. Further, the film thickness of the conductive material 210 is preferably formed so as to be thicker than the film thickness of the thin film metal pad 206 and the film thickness of the thin film metal pad 207.

Next, as shown in FIG. 10C, a through electrode 209 is formed on the second substrate (for example, a glass substrate) 202. A thin film metal pad 207 is formed on one end of the exposed through electrode 209 by a sputtering method or the like. A thin film metal pad 208 is formed on the other end of the exposed through electrode 209 by a sputtering method or the like. The thin film metal pad 207 and the thin film metal pad 208 have, for example, a three-layer laminated structure (for example, Cr / Pt / Au) and are formed with a film thickness of about 100 nm to 5000 nm.

Next, as shown in FIG. 10 (D), the first bonding material 211 (for example, a glass frit material) attaches the functional element 204 and the through electrode 209 on the second substrate 202 by a screen printing method or the like. It is formed so as to surround it. The first bonding material 211 is formed so as to have a film thickness of about 10 μm to 50 μm.

The solvent and the binder are removed by drying and firing the first bonding material 211. Further, the first bonding material 211 is vitrified by being heat-treated at 400 ° C. or higher. As a result, the functional element 204 can be vacuum-sealed when the first substrate 201 and the second substrate 202 are joined.

Next, as shown in FIG. 11 (A), the device substrate (first substrate 201) produced in FIG. 10 (B) and the package substrate (second substrate 202) produced in FIG. 10 (D). ) And, after aligning, join.

The first substrate 201 and the second substrate 202 are pressurized by the joining machine, and the first substrate 201 and the second substrate 202 are further heated (thermocompression bonded). The heating temperature at the time of joining is preferably about 350 ° C. to 450 ° C. That is, it is preferable that the temperature is such that the functional element 204 is not adversely affected and the first bonding material 211 (for example, glass frit material) or conductive material 210 (for example, Ag paste) is fired and cured.

After joining, the conductive material 210 is crushed by heating and pressurizing by a joining machine, and diffusion-bonded with the thin film metal pads 206 and 207. As a result, the conductive material 210 and the thin film metal pads 206 and 207 become conductive.

Further, since the first bonding material 211 is made of a material that is harder than the conductive material 210, it can be considered that the first bonding material 211 is hardly deformed by heating or pressurizing by the bonding machine after bonding. That is, a predetermined distance is maintained between the first substrate 201 and the second substrate 202 by the amount of the film thickness of the first bonding material 211, and the cavity 214 is formed. The functional element 204 is vacuum-sealed in the cavity 214 without forming a separate space in the package substrate. According to the above-mentioned joining step, since the first substrate 201 and the second substrate 202 may be flat plates, unnecessary steps such as separately forming a space for accommodating the functional element 204 can be omitted. ..

Next, as shown in FIG. 11B, a second bonding material 212 (for example, a glass frit material) is formed on the second substrate 202 by a screen printing method or the like. The solvent and the binder are removed by drying and firing the second bonding material 212. Further, the second bonding material 212 is vitrified by being heat-treated at 400 ° C. or higher. As a result, when the first substrate 201 and the third substrate 203 are joined, the functional element 204 can be vacuum-sealed from the opposite direction.

Next, as shown in FIG. 11C, an optical element 213 (for example, an optical filter) is formed on the third substrate 203 by a known microfabrication technique and a semiconductor thin film forming technique.

Next, as shown in FIG. 11 (D), the device substrate (first substrate 201) produced in FIG. 11 (B) and the substrate (third substrate 203) produced in FIG. 11 (C). And are joined after alignment.

The first substrate 201 and the third substrate 203 are pressurized by the joining machine, and the first substrate 201 and the third substrate 203 are further heated (thermocompression bonded). The heating temperature at the time of joining is preferably higher than the heating temperature at the time of joining the first substrate 201 and the second substrate 202.

As described above, the joining of the first substrate 201 and the second substrate 202 and the joining of the first substrate 201 and the third substrate 203 are performed by the first bonding material 211 and the first bonding material 211 in which various conditions are optimized. Highly accurate joining can be performed by individually using the second joining material 212. That is, by optimizing the joining temperature, the thickness, width, and material of the joining material, it is possible to improve the joining strength and joining reliability even when a plurality of substrates on which various elements are formed are overlapped. Therefore, a highly functional device can be realized.

As shown in FIGS. 12 to 15, the device 200 according to the present embodiment may be manufactured by joining all the substrates at the same time.

In this case, first, as shown in FIG. 12 (A), the functional element 204 and the drive circuit 205 are formed on the first substrate 201, and as shown in FIG. 12 (B), the conductive material 210 is formed.

Next, as shown in FIG. 13 (A), a through electrode 209 is formed on the second substrate 202, and as shown in FIG. 13 (B), a first bonding material 211 is formed.

Next, as shown in FIG. 14 (A), the optical element 213 is formed on the third substrate 203, and as shown in FIG. 14 (B), the second bonding material 212 is formed.

Further, as shown in FIG. 15 (A), the positions of the substrate manufactured in FIG. 12 (B), the substrate manufactured in FIG. 13 (B), and the substrate manufactured in FIG. 14 (B). After matching, all the substrates are joined at the same time as shown in FIG. 15 (B).

The joining machine pressurizes the first substrate 201, the second substrate 202, and the third substrate 203, and further heats the first substrate 201, the second substrate 202, and the third substrate 203 ( Thermocompression bonding). The heating temperature at the time of joining is preferably about 350 ° C. to 450 ° C.

As described above, by joining all the substrates at the same time, the manufacturing process can be simplified, so that the manufacturing cost of the device 200 can be suppressed.

Further, as shown in FIG. 16 (A), the first bonding material 211, the second bonding material 212, a plurality of functional elements, and the like are formed on each substrate at the wafer level and then bonded, and then bonded in FIG. 16 (B). As shown in, it is also possible to divide into individual elements and separate them into individual elements.

In this case, since a large number of elements can be formed by a batch process, the manufacturing cost of the device 200 can be suppressed.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and is within the scope of the gist of the embodiment of the present invention described in the claims. Various modifications and changes are possible.

1 1st board
2 Second board
4 Functional elements
5 electrodes
6 through silicon via
11 Joining material
12 Conductive material
14 Third board
100 Device 200 Device 201 First board 202 Second board 203 Third board 204 Functional element 205 Drive circuit 209 Through electrode 210 Conductive material 211 First joint material 212 Second joint material 300 Device 400 Device 500 device

Japanese Unexamined Patent Publication No. 2010-17805 Japanese Unexamined Patent Publication No. 2012-49298 Japanese Unexamined Patent Publication No. 5-291388

Claims (4)

The first substrate on which the optical element is formed and
A second substrate on which an optical sensor in which light transmitted through the optical element is incident is formed , and
A holding portion that joins the first substrate and the second substrate to each other and holds the first substrate and the second substrate at predetermined intervals.
Have,
The holding portion is made of a glass frit material, a polymer resin or a precious metal.
The optical element of the first substrate is made of Si.
A device that features that. The device according to claim 1, wherein the optical sensor is an optical sensor or an infrared sensor. The device according to claim 1 or 2, wherein the optical sensor is vacuum-sealed by the holding portion. The optical element includes a thin film.
The device according to any one of claims 1 to 3, wherein the device is characterized by the above.

Images