JP2010110877A - Electronic device and method for manufacturing electronic device - Google Patents

Abstract

An electronic device capable of effectively suppressing thermal stress transmitted to a MEMS while maintaining a high degree of design freedom.
An electronic device includes: a MEMS unit; a sensor substrate that supports the MEMS unit; and a cap unit that is attached to the sensor substrate so that a recess is opposed to the MEMS unit. 2. An electronic device according to claim 1, wherein a stress absorbing portion having a concavo-convex structure having a thickness smaller than that of the joint portion with the sensor substrate is formed on a part of the wall surface.
[Selection] Figure 1

Description

  The present invention relates to an electronic device having a structure in which a MEMS (Micro Electro Mechanical Systems) portion is installed on a sensor substrate and sealed with a cap, and a method for manufacturing the same.

  2. Description of the Related Art Conventionally, electronic parts including parts including mechanical parts such as MEMS and a control IC (circuit chip) are used. MEMS is defined as a device in which mechanical parts, sensors, actuators, electronic circuits, and the like are integrated on a single silicon substrate, glass substrate, organic material, and the like.

  One of the problems with such electronic components is that the MEMS is strongly subjected to stress due to the difference between the linear expansion coefficients of other structures and electronic components to be mounted, or the sensor substrate and cap of the electronic components. There are problems of detection, characteristic fluctuations, failures, and the like.

An invention relating to a capacitive sensor in consideration of such a point is disclosed (for example, see Patent Document 1). In this sensor, a groove is formed in an insulating substrate to which a semiconductor substrate is attached, thereby preventing thermal stress from being transmitted to the semiconductor substrate.
Japanese Patent Laid-Open No. 11-281667

  However, in the conventional sensor described above, a groove is formed in the insulating substrate to which the semiconductor substrate is attached, which causes a problem that the degree of freedom in design is reduced.

  The present invention is for solving such problems, and provides an electronic device capable of effectively suppressing the thermal stress transmitted to the MEMS while maintaining a high degree of design freedom. The main purpose.

In order to achieve the above object, the first aspect of the present invention provides:
A MEMS section;
A sensor substrate for supporting the MEMS unit;
A cap portion attached to the sensor substrate such that the concave portion faces the MEMS portion;
An electronic device comprising:
A part of the wall surface of the cap portion is formed with a stress absorbing portion having a concavo-convex structure with a thickness reduced as compared with a joint portion with the sensor substrate.
It is an electronic device.

  According to the first aspect of the present invention, the concave and convex portions having a thickness smaller than that of the joint portion with the sensor substrate are formed on a part of the wall surface of the cap portion attached to the sensor substrate so that the concave portion faces the MEMS portion. Since the stress absorbing portion of the structure is formed, the thermal stress transmitted to the MEMS can be effectively suppressed.

  In addition, since the stress absorbing portion is formed not on the sensor substrate but on the cap portion, the degree of freedom in design can be increased.

  Furthermore, since the joint part between the cap part and the sensor substrate can be made thicker than the stress absorbing part thinned to absorb the stress by enabling bending, it is possible to suppress the breakage of the joint part. Can do.

The second aspect of the present invention is:
A method of manufacturing an electronic device having a structure in which a MEMS unit is installed on a sensor substrate and sealed with a cap,
Forming a cavity in a multilayer SOI wafer;
Forming, by side etching, a stress-absorbing portion having a concavo-convex structure having a thickness reduced as compared with a joint portion with the sensor substrate on the multilayer SOI wafer;
Bonding the multilayer SOI wafer and the sensor substrate;
Dividing the member obtained by bonding the multilayer SOI wafer and the sensor substrate by dicing;
The manufacturing method of the electronic device which has this.

  ADVANTAGE OF THE INVENTION According to this invention, the electronic device which can suppress effectively the thermal stress transmitted to MEMS can be provided, maintaining the freedom degree of design high.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the accompanying drawings. The electronic device according to the present invention is used as, for example, an angular velocity sensor, an acceleration sensor, a pressure sensor, etc., and has a structure in which a MEMS (Micro Electro Mechanical Systems) part is installed on a sensor substrate and is sealed with a cap. Have

<First embodiment>
Hereinafter, an electronic device 1 according to a first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view schematically illustrating the configuration of an electronic device 1 according to a first embodiment of the present invention. As illustrated, the electronic device 1 includes a MEMS structure (movable part) 10, a sensor substrate 20, and a cap 30, and the sensor substrate 20 and the cap 30 are joined by a joining portion 40.

  The MEMS structure 10 has a movable part, which is a mechanical part, and other necessary electronic circuits. The MEMS structure 10 is formed, for example, based on an SOI substrate, and a movable portion is formed by performing trench etching, release etching, or the like on a silicon layer in the SOI substrate. The movable part of the MEMS structure 10 is connected to the active layer 22 of the sensor substrate 20 by a beam having a spring property or the like.

  The sensor substrate 20 has a configuration in which an active layer 22 is bonded to a support substrate 26 by a buried oxide film 24. The configuration of the sensor substrate 20 is not limited to this and may have any configuration. For example, a configuration without the buried oxide film 24 may be used.

  The cap 30 is joined to the sensor substrate 20 (the active layer 22; hereinafter omitted) so that the cavity (concave portion) 32 faces the MEMS structure 10. As a result, the MEMS structure 10 can be substantially shielded from the outside air to suppress problems due to the inclusion of foreign matter, and the cavity 32 can be decompressed by hermetic sealing to increase the degree of freedom in designing the electronic device 1.

  In addition, a stress absorbing portion 35 having a concavo-convex structure having a thickness smaller than that of the joint portion 40 with the sensor substrate 20 is formed on part of the wall surface of the cap 30. In this embodiment, the cap 30 has a structure in which the side corresponding to the outer wall of the electronic device 1 is partially removed.

  With such a configuration, the stress absorbing portion 35 can flex more flexibly in response to an external force, and the difference between the linear expansion coefficients of other structures to be mounted and the electronic device 1 or the sensor substrate 20 and the cap 30 can be increased. It is possible to effectively suppress the influence of the stress due to the stress on the MEMS 10.

  Further, since the stress absorbing portion 35 is formed not on the sensor substrate 20 but on the cap 30, the degree of freedom in design can be increased.

  Furthermore, since the joint portion 40 between the cap 30 and the sensor substrate 20 can be made thicker than the stress absorbing portion 35, the joint portion 40 can be prevented from being damaged.

  The electronic device 1 having such effects can be manufactured, for example, according to the following steps. 2 and 3 are explanatory diagrams for explaining a manufacturing process of the electronic device 1. Although these drawings are shown to manufacture one electronic device 1, in reality, a plurality of electronic devices 1 are manufactured simultaneously from one wafer, and in the process of FIG. It will be separated into individual pieces.

First, as shown in FIG. 2A, a multilayer SOI wafer in which Si and SiO ₂ are alternately laminated is prepared.

  Next, as shown in FIG. 2B, a groove A to be the cavity 32 and a dividing groove B for facilitating the process of FIG. 3C to be described later are formed by anisotropic etching. Anisotropic etching includes those using an active gas such as SF6 and those using an alkaline aqueous solution such as KOH and TMAH. Note that the process of forming the dividing groove B may be omitted.

  Then, as shown in FIG. 2C, the anisotropically etched wafer is bonded to the sensor substrate 20 on which the MEMS structure 10 is formed. For the joining, a technique such as glass frit or metal eutectic joining is used.

  When the wafer is bonded to the sensor substrate 20, as shown in FIG. 3A, up to one layer of the dividing groove B is cut by dicing.

Then, as shown in FIG. 3B, about half of the SiO ₂ layer is removed by side etching. As a result, the structure of the stress absorbing portion 35 is completed. For side etching, vapor hydrofluoric acid (Vaper HF) or the like is used.

  Finally, the Si layer and the sensor substrate left in the step of FIG. 3A are divided by dicing, and the chips are separated.

  According to the electronic apparatus 1 of the present embodiment described above, the thermal stress transmitted to the MEMS structure 10 can be effectively suppressed while maintaining a high degree of design freedom.

<Second embodiment>
Hereinafter, an electronic device 2 according to a second embodiment of the present invention will be described. FIG. 4 is a cross-sectional view schematically showing the configuration of the electronic device 2 according to the second embodiment of the present invention. As illustrated, the electronic device 2 includes a MEMS structure (movable part) 10, a sensor substrate 20, and a cap 30, and the sensor substrate 20 and the cap 30 are joined by a joining portion 40. Since the electronic device 2 is common to the electronic device 1 of the first embodiment except for the structure of the cap 30, only the structure and manufacturing process of the cap 30 will be described.

  The cap 30 according to the second embodiment is joined to the sensor substrate 20 so that the cavity (concave portion) 32 faces the MEMS structure 10 as in the first embodiment. As a result, the MEMS structure 10 can be substantially shielded from the outside air to suppress problems due to the inclusion of foreign matter, and the cavity 32 can be decompressed by hermetic sealing to increase the degree of freedom in designing the electronic device.

  In addition, a stress absorbing portion 35 having a concavo-convex structure having a thickness smaller than that of the joint portion 40 with the sensor substrate 20 is formed on a part of the wall surface of the cap 30. Unlike the first embodiment, the present embodiment has a structure in which the side of the cap 30 corresponding to the outer wall and the inner wall of the electronic device 1 is partially removed.

  The effect produced by such a configuration is the same as that of the first embodiment.

In the electronic device 2 having such an effect, for example, in the step of FIG. 2B in the first embodiment, a step of removing about 1/4 of the SiO ₂ layer from the inner side (side to be the cavity 32) by side etching. It can be manufactured by adding. FIG. 5 is a diagram showing a step of removing about 1/4 of the SiO ₂ layer from the inside by side etching. In addition, compared with 1st Example, the quantity removed in the process of FIG.3 (B) is decreased, and the thickness of the stress absorption part 35 is adjusted.

  According to the electronic apparatus 2 of the present embodiment described above, the thermal stress transmitted to the MEMS structure 10 can be effectively suppressed while maintaining a high degree of design freedom.

<Third embodiment>
Hereinafter, an electronic device 3 according to a third embodiment of the present invention will be described. FIG. 6 is a cross-sectional view schematically illustrating the configuration of the electronic device 2. As illustrated, the electronic device 3 includes a MEMS structure (movable part) 10, a sensor substrate 20, and a cap 30, and the sensor substrate 20 and the cap 30 are joined by a joining portion 40. Since the electronic device 3 is common to the electronic device 1 of the first embodiment except for the structure of the cap 30, only the structure and manufacturing process of the cap 30 will be described.

  The cap 30 according to the third embodiment is joined to the sensor substrate 20 so that the cavity (concave portion) 32 faces the MEMS structure 10 as in the first embodiment. As a result, the MEMS structure 10 can be substantially shielded from the outside air to suppress problems due to the inclusion of foreign matter, and the cavity 32 can be decompressed by hermetic sealing to increase the degree of freedom in designing the electronic device.

  In addition, a stress absorbing portion 35 having a concavo-convex structure having a thickness smaller than that of the joint portion 40 with the sensor substrate 20 is formed on a part of the wall surface of the cap 30. In this embodiment, unlike the first embodiment, the side of the cap 30 corresponding to the inner wall of the electronic device 1 is partially removed.

  The effect produced by such a configuration is the same as that of the first embodiment.

In the electronic device 3 having such an effect, for example, a step of removing about half of the SiO ₂ layer from the inner side (side to be the cavity 32) by side etching is added to the step of FIG. 2B in the first embodiment. It can be manufactured by omitting the step of FIG. FIG. 7 is a diagram showing a state in which a step of removing about half of the SiO ₂ layer from the inner side (side to be the cavity 32) by side etching is added.

  According to the electronic apparatus 3 of the present embodiment described above, the thermal stress transmitted to the MEMS structure 10 can be effectively suppressed while maintaining a high degree of design freedom.

<Effect confirmation by simulation>
In order to confirm the effect of the embodiment described above, the present applicant performed the following simulation.

  First, an electronic device having a conventional structure that does not have a stress absorbing portion, an electronic device having a structure similar to that of the first embodiment, and a 1/4 model of an electronic device having a structure similar to that of the first embodiment (model 1 and model respectively) 2, referred to as Model 3). FIG. 8 is a schematic view of these models and an enlarged view of the vicinity of the joint. FIG. 9 is a diagram illustrating the dimensions of the wall surface, the stress absorbing portion, and the joint portion in each model.

  The cap and the sensor substrate were made of Si, and these joint portions were joined at 450 [° C.] by Al—Al eutectic joining. The linear expansion coefficient of Si is 2.5 [ppm / ° C], the Young's modulus is 150 [GPa], and the Poisson's ratio is 0.36. Moreover, the linear expansion coefficient of Al is 23.1 [ppm / ° C], the Young's modulus is 77 [GPa], and the Poisson's ratio is 0.30. Note that 450 [° C.] was used as a reference (stress = 0).

  Under such setting, the temperature condition of the electronic device is reduced to (1) 450 [° C] → 440 [° C], and the position where the MEMS structure is installed on the support base ((1) in FIG. 8) Stress at the position of the electrode and the counter electrode). Further, (2) The stress was calculated in the same manner by reducing the temperature from 450 [° C] to 27 [° C].

  As a result, in the simulation (1), 0.049 [MPa] in the model 1, 0.026 [MPa] in the model 2, and 0.033 [MPa] in the model 3 were obtained.

  In the simulation (2), the results of 1.440 [MPa] in model 1, 0.770 [MPa] in model 2, and 0.965 [MPa] in model 3 were obtained.

  That is, the stress applied to the MEMS structure is reduced in the first embodiment by about 47 [%] compared to the electronic device having the conventional structure that does not include the stress absorbing portion, and in the second embodiment by about 33 [%]. The result that can be.

<Modification>
The best mode for carrying out the present invention has been described above with reference to the embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the present invention. And substitutions can be added.

<Deformation 1>
For example, in any one of the first embodiment, the second embodiment, and the third embodiment, the shape of the cavity 32 may be varied as shown in FIG. In FIG. 10, the shape of the stress absorbing portion 35 is shown as conforming to the first embodiment.

  In this case, the process shown in FIG. 11 is performed in place of the process of FIG. The grooves C and D are formed by anisotropic etching, and the gap between the grooves C and D is removed by anisotropic etching for a height necessary for housing the MEMS structure 10.

  By doing so, the etching amount can be reduced, and in addition to the effects described in the first to third embodiments, the manufacturing time can be shortened.

<Deformation 2>
Further, in any one of the first embodiment, the second embodiment, and the third embodiment, as shown in FIG. 12, both surfaces or one side of the ceiling portion 33 of the cap 30 are etched, and a part of the ceiling portion 33 is thinned. May be. In FIG. 12, the shape of the stress absorbing portion 35 is shown as conforming to the first embodiment.

  By doing so, the cap 30 is further increased in flexibility, so that the thermal stress transmitted to the MEMS structure 10 can be further suppressed.

<Modification 3>
Further, in any one of the first embodiment, the second embodiment, and the third embodiment, as shown in FIG. 13, both surfaces or one side of the ceiling portion 33 of the cap 30 are etched, and lattice-like slits are formed in the ceiling portion 33. It may be formed. FIG. 13 shows the shape of the stress absorbing portion 35 as conforming to the first embodiment.

  By doing so, the cap 30 is further increased in flexibility, so that the thermal stress transmitted to the MEMS structure 10 can be further suppressed.

<Others>
In addition, expressions such as “removing about half of the SiO ₂ layer” and “removing about 1/4” are merely examples, and other degrees of removal may be employed. It is not limited to a numerical value of “about 1/4”.

  The present invention can be used in the automobile manufacturing industry, the automobile parts manufacturing industry, and the like.

1 is a cross-sectional view schematically illustrating a configuration of an electronic device 1 according to a first embodiment of the present invention. FIG. 6 is an explanatory diagram for explaining a manufacturing process of the electronic device 1. FIG. 6 is an explanatory diagram for explaining a manufacturing process of the electronic device 1. It is sectional drawing which shows the outline of a structure of the electronic device 2 which concerns on 2nd Example of this invention. The SiO ₂ layer by side etching from the inside (the side where the cavity 32) shows the step of removing about 1/4. It is sectional drawing which shows the outline of a structure of the electronic device 3 which concerns on 3rd Example of this invention. The side etching is a diagram showing a process for about half removed SiO ₂ layer from the inside (the side where the cavity 32). It is the schematic of the model used by simulation, and the enlarged view near a junction part. It is a figure which shows the dimension of the wall surface in each model, a stress absorption part, and a junction part. It is sectional drawing which shows the outline of a structure at the time of changing the shape of the cavity 32 in any one of 1st Example, 2nd Example, and 3rd Example. It is explanatory drawing for demonstrating a part of process for manufacturing the electronic device which has a structure of FIG. It is sectional drawing which shows the outline of a structure at the time of etching the both surfaces or one side of the ceiling part 33 of the cap 30, and making a part of ceiling part 33 thin. FIG. 4 is a cross-sectional view schematically showing a configuration when both surfaces or one side of a ceiling portion 33 of a cap 30 are etched to form a lattice-like slit in the ceiling portion 33.

Explanation of symbols

1, 2, 3 Electronic device 10 MEMS structure 20 Sensor substrate 22 Active layer 24 Embedded oxide film 26 Support substrate 30 Cap 32 Cavity 33 Ceiling part 35 Stress absorbing part 40 Joint part

Claims (2)

A MEMS section;
A sensor substrate for supporting the MEMS unit;
A cap portion attached to the sensor substrate such that the concave portion faces the MEMS portion;
An electronic device comprising:
A part of the wall surface of the cap portion is formed with a stress absorbing portion having a concavo-convex structure with a thickness reduced as compared with a joint portion with the sensor substrate.
Electronic equipment. A method of manufacturing an electronic device having a structure in which a MEMS unit is installed on a sensor substrate and sealed with a cap,
Forming a cavity in a multilayer SOI wafer;
Forming, by side etching, a stress-absorbing portion having a concavo-convex structure having a thickness reduced as compared with a joint portion with the sensor substrate on the multilayer SOI wafer;
Bonding the multilayer SOI wafer and the sensor substrate;
Dividing the member obtained by bonding the multilayer SOI wafer and the sensor substrate by dicing;
Manufacturing method of electronic device having