JP6747786B2 - MEMS device, MEMS switch, and manufacturing method of MEMS switch - Google Patents

Description

The present invention relates to a MEMS (Micro Electro Mechanical System) device, a MEMS switch, and a method for manufacturing a MEMS switch.

Japanese Unexamined Patent Application Publication No. 2005-342803 discloses a MEMS device in which a seal glass serving as a protective cover is bonded onto a module substrate via a frame-shaped seal metal layer (sealing portion) surrounding a MEMS element portion. In this MEMS device, an interlayer insulating layer having a two-layer structure of SiO ₂ and SiO formed by a CVD method is formed so as to cross a signal transmission wiring (metal transmission line), and a seal is formed on the interlayer insulating layer. A metal layer (sealing portion) is formed.

JP, 2005-342803, A

However, it has been found that the interlayer insulating layer formed by the CVD method or the like as in the past has poor adhesion to the metal transmission line. If the adhesion of this portion is poor, there is a problem in that, when wet etching or the like is performed at the time of manufacturing, a part of the interlayer insulating layer is destroyed and a leakage path of the etching solution is formed.

An object of the present invention is to provide a MEMS device and a MEMS switch that have high adhesion to a transmission line and an insulating layer.

A method of the present invention is to provide a method of manufacturing a MEMS switch having high adhesion to a transmission line and an insulating layer.

The present invention relates to a device substrate in which a device driven, controlled, or read by an electric signal is arranged on the surface of a first substrate, and a transmission line substrate in which a metal transmission line is arranged on the surface of a second substrate. , An insulating layer formed by a thin film forming technique and etching on the surface of the second substrate so as to cross the transmission line, and hermetically sealing the device by being arranged between the insulating layer and the surface of the first substrate As described above, the target is a MEMS device including a sealing portion that joins the first substrate and the second substrate. In particular, in the present invention, a thin film adhesion layer made of a material having an insulation property and having a higher (high frequency) insulation property than the insulation layer is formed on the transmission line so as to adhere to both the transmission line and the insulation layer. ing.

According to the present invention, by providing the thin film adhesion layer made of a material that adheres to both the transmission line and the insulating layer, the adhesion between the high frequency transmission line and the insulating layer can be made higher than before. The leakage path of the etching liquid is not formed between the transmission line and the insulating layer. Therefore, it is possible to provide a MEMS device with higher reliability than ever before. In particular, since the thin film adhesion layer is formed of a material having a higher (high frequency) insulating property than the insulating layer, an advantage of suppressing transmission loss can be obtained.

The thin film adhesion layer can be formed from an aluminum oxide film. The thickness may be 200 nm or less. When the thickness of the thin film adhesion layer is 200 nm or less, sufficient adhesion can be ensured and the film formation does not take longer than necessary. In particular, aluminum oxide can be formed inexpensively and easily by a thin film forming technique, so that a highly reliable MEMS device can be provided without increasing the price of the MEMS device.

The first substrate and the second substrate can each be formed from a silicon substrate. The transmission line is preferably made of Au or Cu having a thickness of 1 μm or more. The insulating layer can be formed of SiO _{2 having} a thickness of 3 μm or more. Of course, the insulating layer may have a two-layer structure of SiO ₂ and SiO.

The sealing portion is preferably formed of a metal layer that flattens the step due to the transmission line. The thickness of the sealing portion is preferably 1 μm or more larger than the thickness of the transmission line. In this way, the step due to the transmission line is absorbed and the sealing portion can be reliably formed.

The device is arbitrary, but when the device is a MEMS switch element, the MEMS switch can be specifically configured as follows. That is, the MEMS switch includes a device substrate in which a MEMS switch element driven and controlled by an electric signal is arranged on the surface of the first silicon substrate, and a transmission made of Au having a thickness of 1 μm or more on the surface of the second silicon substrate. A transmission line substrate on which the line is arranged, an insulating layer made of SiO ₂ and having a thickness of 3 μm or more formed on the surface of the second silicon substrate so as to cross the transmission line, and the insulating layer and the first silicon substrate. A sealing portion that is disposed between the first silicon substrate and the second silicon substrate by metal bonding so as to hermetically seal the MEMS switch element, is provided between the surface and the high frequency transmission line made of Au. A thin film adhesion layer of aluminum oxide having a thickness of 200 nm or less is formed.

Further, as a manufacturing method of the MEMS switch, it is preferable to adopt the following method. That is, a device substrate manufacturing step of forming a MEMS switch element which is driven and controlled by an electric signal on the surface of the first silicon substrate by a MEMS forming technique, and a transmission of Au having a thickness of 1 μm or more on the surface of the second silicon substrate. A transmission line substrate manufacturing step of forming the line by a thin film forming technique; an adhesion layer forming step of forming a thin film adhesion layer made of aluminum oxide and having a thickness of 200 nm or less on the transmission line made of Au by the thin film forming technique; And an insulating layer forming step of forming an insulating layer of SiO _{2 having} a thickness of 3 μm or more formed on the surface of the second silicon substrate so as to cross the thin film adhesion layer by a thin film forming technique such as a CVD method; A sealing portion is provided between the first silicon substrate and the surface of the first silicon substrate to join the first silicon substrate and the second silicon substrate by metal bonding so as to hermetically seal the MEMS switch element. A first metal layer is formed on the substrate by sputtering, a second metal layer is formed on the second silicon substrate by electrolytic plating, and then the first metal layer and the second metal layer are metal-bonded to each other. It is preferable to manufacture the MEMS switch from the step of forming the sealing portion. According to this method, the MEMS switch can be manufactured at low cost.

According to the MEMS device and the MEMS switch of the present invention, the adhesion between the transmission line and the insulating layer is high, and a part of the interlayer insulating layer is not destroyed to form a leakage path of the etching solution. Can be realized without a significant increase in cost. Further, according to the manufacturing method of the MEMS switch of the present invention, such a MEMS switch can be manufactured at low cost.

FIG. 3 is an end view showing a main part of one embodiment of the MEMS switch of the present invention, taken along the line II′ of FIG. 2. It is a perspective view which shows the embodiment of FIG. It is a top view which shows the 2nd board|substrate of embodiment of FIG. FIG. 3 is a step diagram for manufacturing the device substrate according to the embodiment of FIG. 1 and an end view showing the device substrate. (A) And (B) is a high frequency line manufacturing step drawing of embodiment of FIG. 1, respectively, and is an AA' end view and a BB' end view of FIG. (A) And (B) is an adhesion layer formation step drawing similar to FIG. 5, respectively. 5A and 5B are insulating layer formation step diagrams similar to FIG. (A) And (B) is a sealing part formation step drawing (the 1) similar to FIG. 5, respectively. (A) And (B) is a sealing part formation step drawing (the 2) similar to FIG. 5, respectively.

Hereinafter, embodiments of a MEMS device, a MEMS switch, and a manufacturing method of the MEMS switch according to the present invention will be described.

1 and 2 show a cross-sectional view and an assembly schematic diagram of one embodiment of a MEMS switch according to the present invention. FIG. 3 is a plan view showing the second substrate 20 and each layer formed on the surface of the second substrate 20 in the embodiment shown in FIGS. 1 and 2, and FIG. 4 in the same embodiment. FIG. 3 is an end view showing the first substrate 10 and each layer formed on the surface of the first substrate 10.

In each figure, on the surface (upper surface in FIG. 4, lower surface in FIG. 1) of a first silicon substrate made of Si, that is, first substrate 10, a first metal layer 12 made of Au and a cantilever 14 made of a piezoelectric thin film are formed. And are stacked. The cantilever 14 is fixed to the surface of the first substrate 10 near the left end (fixed end) in FIGS. 1 and 2, and the right end is above the recess 11 formed on the surface of the first substrate 10. It is a free end that extends. A drive control electrode connecting portion 16 made of Au is formed on the surface near the left end of the cantilever 14, and a switch contact 18 made of Au is formed on the surface near the right end by sputtering.

A frame-shaped first metal layer 12 made of Au is formed by sputtering together with the drive control electrode connecting portion 16 and the switch contact portion 18. As shown in FIG. 2, the first metal layer 12 forms a continuous rectangular enclosure (or frame) when viewed in the plane of the first substrate 10. The shape of is the same as the shape of the second metal layer 25 made of Au formed by electrolytic plating on the side of the second substrate 20 described later. Therefore, by metal-bonding the first metal layer 12 and the second metal layer 25, it is possible to form a sealed space that protects the movable portion of the device.

Such a device substrate can be formed by a conventional MEMS forming technique. For example, the step of forming the concave portion 11 in the first substrate 10, the step of flattening the concave portion 11 with resin and patterning into the shape of the cantilever 14, the first metal layer 12, the drive control electrode connecting portion 16, It can be formed through a step of forming the switch contact portion 18 and a step of removing the resin in the concave portion 11 in order to make the free end of the cantilever 14 movable.

The thickness of the first metal layer 12 made of Au formed by sputtering is, for example, about 2 μm, the thickness of the drive control electrode connecting portion 16 and the switch contact portion 18 is, for example, about 0.8 μm, and the thickness of the cantilever 14 is, for example, It is about 1.2 μm.

Note that the thickness of each layer in each drawing is different from the actual thickness and is exaggerated for convenience of description. Therefore, in some cases, it is thicker than the ratio of the form actually manufactured.

The device substrate of this embodiment is a cantilever (cantilever) type RF-MEMS switch substrate. However, in other embodiments, a double-supported beam type or thin film type switch substrate may be used, and further, a sensor substrate such as an acceleration sensor or a pressure sensor, or a device substrate such as a reading probe for a recording medium may be used.

On the surface of the second silicon substrate 20 made of Si, the surface of which is thermally oxidized, that is, the second substrate 20, a high frequency line 21 made of Au and a drive control electrode 22 are arranged to form a transmission line substrate. An insulating layer 24 is formed on the surface of the second substrate 20 so as to cross the high-frequency line 21 via a thin film adhesion layer 23. A second metal layer 25 that joins the first substrate 10 and the second substrate 20 is provided between the insulating layer 24 and the surface of the first substrate 10 so as to hermetically seal the device. .. The second metal layer 25 is a thin film of Au formed by electrolytic plating. The drive control electrode 22 and the drive control electrode connection portion 16 are connected by a drive control electrode connection bump 26.

In the present embodiment, as shown in FIG. 9B, there is an insulating property between the high frequency line 21 and the insulating layer 24 and a higher (high frequency) insulating property than the insulating layer 24. A thin film adhesion layer 23 made of a material is formed. Thus, by providing the thin film adhesion layer 23 made of a material that adheres to both the high frequency line 21 and the insulating layer 24, the adhesion between the high frequency line 21 and the insulating layer 24 can be made higher than before. As a result, no leakage path is formed between the high frequency line 21 and the insulating layer 24. Therefore, it is possible to provide a MEMS switch with higher reliability than before. In particular, since the thin film adhesion layer 23 is formed of a material having a higher (high frequency) insulating property than the insulating layer 24, an advantage of suppressing transmission loss can be obtained.

The thin film adhesion layer 23 can be formed of an aluminum oxide film. The thickness may be 200 nm or less. When the thickness of the thin film adhesion layer 23 is 200 nm or less, sufficient adhesion can be ensured and the film formation does not take longer than necessary. In particular, aluminum oxide can be formed inexpensively and easily by the thin film forming technique, so that a highly reliable MEMS switch can be realized without increasing the price of the MEMS device.

In the RF-MEMS switch according to the present embodiment, the cantilever 14 having flexibility is bent downward by passing a current through the drive control electrode 22, so that the switch contact portion 18 arranged near the free end is 3 times. The middle high-frequency line 21 of the book can be connected to perform operations such as switching the circuit configuration.

In this embodiment, each of the first substrate 10 and the second substrate 20 is a silicon substrate, but in other embodiments, it may be a glass substrate. The high-frequency line 21 may be Au having a thickness of 1 μm or more, but may be Cu. The insulating layer 24 can be formed of SiO ₂ having a thickness of 3 μm or more. Of course, in other embodiments, the insulating layer may have a two-layer structure of SiO ₂ and SiO.

In the present embodiment, the second metal layer 25 is formed of an Au layer that flattens the step due to the high frequency line 21, but Cu or another metal can also be used. The thickness of the second metal layer 25 is larger than the thickness of the high-frequency line 21 by 1 μm or more. In this way, the step due to the high-frequency line 21 is absorbed and the second metal layer 25 can be reliably formed.

Although the MEMS device of this embodiment is an RF-MEMS switch, the MEMS device to which the present invention is applied is optional as described above. When the MEMS device is the MEMS switch element of this embodiment, the MEMS switch manufacturing method of this embodiment described with reference to FIG.

That is, the MEMS switch of the present embodiment shown in FIGS. 1 to 3 includes a device substrate in which a MEMS switch element driven and controlled by an electric signal is arranged on the surface of a first substrate 10 made of silicon, and a silicon substrate. A transmission line substrate in which a high frequency line 21 made of Au having a thickness of 1 μm or more is arranged on the surface of the second substrate 20, and SiO ₂ formed on the surface of the second substrate 20 so as to cross the high frequency line 21. An insulating layer 24 having a thickness of 3 μm or more, and a sealing portion which is disposed between the insulating layer 24 and the surface of the first substrate 10 and hermetically seals the MEMS switch element. The first metal layer 12 made of Au is provided on the first substrate 10, the second metal layer 25 made of Au is provided on the second substrate 20, and the aluminum oxide is formed on the high frequency line 21 made of Au. The thin film adhesion layer 23 having a thickness of 200 nm or less is formed.

First, in the device substrate manufacturing step of FIG. 4, a device substrate in which a MEMS switch element driven and controlled by an electric signal is arranged on the surface of the first substrate 10 made of silicon is formed by a conventional MEMS forming technique. The fact that the first metal layer 12 made of Au is formed on the first substrate 10 by sputtering is as described above. In each manufacturing step of the second substrate 20 shown in FIGS. 5 to 9, the first metal layer 12 made of Au and the second metal layer 25 made of Au are finally joined to form a sealing portion. However, by the time when the MEMS switch as shown in FIG. 1 is almost completed, it is performed before, after, or in parallel with the device substrate manufacturing step of FIG.

In the high frequency line manufacturing step of FIGS. 5A and 5B, the high frequency line 21 made of Au having a thickness of 1 μm or more and the drive control electrode 22 are formed on the surface of the second substrate 20 by electrolytic plating.

In the adhesion layer forming step of FIGS. 6A and 6B, a thin film adhesion layer 23 made of aluminum oxide and having a thickness of 200 nm or less is formed on the high frequency line 21 made of Au and the drive control electrode 22 by a thin film forming technique. Form.

In the insulating layer forming step of FIGS. 7A and 7B, a thickness of 3 μm made of SiO ₂ is formed on the surface of the second substrate 20 so as to cross the high frequency line 21, the drive control electrode 22 and the thin film adhesion layer 23. The above insulating layer 24 is formed by a thin film forming technique such as a CVD method.

8A and 8B, the Au layer is laminated on the insulating layer 24 formed on the surface of the second substrate 20 by electrolytic plating to form the second metal layer 25. Form. Prior to this, a part of the thin film adhesion layer 23 and the insulating layer 24 laminated on the surface of the drive control electrode 22 is removed and flattened by the Au layer which is the second metal layer to connect the drive control electrode. The bumps 26 are formed simultaneously with the second metal layer 25.

In the sealing portion forming step (2) of FIGS. 9A and 9B, the insulating layer 24 other than the portion covered by the second metal layer 25 is removed, so that the steps shown in FIGS. A square enclosure is formed as shown.

Finally, as shown in FIG. 1, the device substrate shown in FIG. 4 and the high-frequency line substrate shown in FIGS. 9A and 9B are turned upside down, and the second metal layer 25 and the first metal layer 12 are provided. Are overlapped with each other so as to be coincident with each other, and the both are metal-bonded to each other to complete the step of forming the sealing portion and complete the sealing.

According to the method of manufacturing the MEMS switch according to the present embodiment, the high-frequency line 21 and the insulating layer 24 have high adhesiveness, and therefore, the MEMS switch in which the leakage path of the etching liquid is hard to be formed can be manufactured at low cost.

According to the present invention, by providing the thin film adhesion layer made of a material that adheres to both the transmission line and the insulating layer, the adhesion between the high frequency transmission line and the insulating layer can be made higher than before. The leakage path of the etching liquid is not formed between the transmission line and the insulating layer. Therefore, it is possible to provide a more reliable MEMS device and MEMS switch than ever before.

10 First Substrate 11 Recess 12 First Metal Layer 14 Cantilever 16 Drive Control Electrode Connection 18 Switch Connection 20 Second Substrate 21 High Frequency Line 22 Drive Control Electrode 23 Thin Film Adhesion Layer 24 Insulating Layer 25 Second Metal layer 26 Drive control electrode connection bump

Claims (12)

A device substrate manufacturing step of forming a MEMS switch element, which is driven and controlled by an electric signal, on the surface of the first silicon substrate by a MEMS forming technique;
A transmission line substrate manufacturing step of forming a metal transmission line on the surface of the second silicon substrate by a thin film forming technique;
An adhesion layer forming step of forming a thin film adhesion layer on the transmission line by sputtering or vacuum deposition,
An insulating layer forming step an insulating layer you insulation on said surface of said second silicon substrate so as to traverse the transmission line and the thin film adhesion layer formed by a thin film forming technique and etching,
The first silicon substrate and the second silicon substrate are bonded by metal bonding so as to be arranged between the insulating layer and the surface of the first silicon substrate to hermetically seal the MEMS switch element. And a sealing portion forming step of forming a sealing portion,
The method for manufacturing a MEMS switch, wherein the thin film adhesion layer is made of a material having higher insulation than the insulation layer. The transmission line is made of Au having a thickness of 1 μm or more,
The insulating layer is made of SiO ₂ having a thickness of 3 μm or more,
The thin film forming technique is a CVD method,
In the step of forming the sealing portion, a first metal layer is formed on the first silicon substrate by sputtering, a second metal layer is formed on the second silicon substrate by electrolytic plating, and then the first metal layer is formed. 2. The method of manufacturing a MEMS switch according to claim 1, wherein the metal layer and the second metal layer are metal-bonded to each other to form the sealing portion. A device substrate on which a device driven, controlled, or read by an electric signal is arranged on the surface of the first substrate;
A transmission line substrate in which a metal transmission line is arranged on the surface of the second substrate;
An insulating layer formed on the surface of the second substrate so as to cross the transmission line;
A MEMS device comprising a sealing portion that is disposed between the insulating layer and the surface of the first substrate and that joins the first substrate and the second substrate so as to hermetically seal the device. There
On the transmission line, a thin film adhesion layer made of a material having an insulation property and having a higher insulation property than the insulation layer, which is in close contact with both the transmission line and the insulation layer, is formed. MEMS device to do. The MEMS device according to claim 3, wherein the transmission line is a high-frequency transmission line. The MEMS device according to claim 3, wherein each of the first substrate and the second substrate is a silicon substrate. The MEMS device according to claim 3, wherein the transmission line is made of Au or Cu having a thickness of 1 μm or more. The MEMS device according to claim 3, wherein the insulating layer is made of SiO ₂ having a thickness of 3 μm or more. The MEMS device according to claim 3, wherein the sealing portion is a metal layer that flattens a step due to the transmission line, and has a thickness greater than the thickness of the transmission line by 1 μm or more. The MEMS device according to claim 4, wherein the thin film adhesion layer is made of an aluminum oxide film. The MEMS device according to claim 9, wherein the thin film adhesion layer has a thickness of 200 nm or less. The MEMS device according to claim 3, wherein the device is a MEMS switch element. A device substrate in which a MEMS switch element driven and controlled by an electric signal is arranged on the surface of the first silicon substrate;
A transmission line substrate in which a transmission line made of Au having a thickness of 1 μm or more is arranged on the surface of the second silicon substrate;
An insulating layer made of SiO ₂ and having a thickness of 3 μm or more formed on the surface of the second silicon substrate so as to cross the transmission line;
A seal that is disposed between the insulating layer and the surface of the first silicon substrate to bond the first silicon substrate and the second silicon substrate by metal bonding so as to hermetically seal the MEMS switch element. With a stop,
A MEMS switch, wherein a thin film adhesion layer made of aluminum oxide and having a thickness of 200 nm or less is formed on the transmission line made of Au.