JP4494130B2 - Manufacturing method of electrostatic drive switch - Google Patents

Description

  The present invention relates to an electrostatic drive switch formed on a semiconductor substrate by micromachine technology and a method for manufacturing the same, and more particularly to a structure capable of being manufactured integrally with a semiconductor integrated circuit and for sealing. The present invention relates to a switch structure integrated with a switch and a manufacturing method thereof.

  Various micromachines manufactured on a silicon substrate are widely used in various application fields (see Non-Patent Document 1). Silicon can be obtained in large quantities at low cost, and it can be easily miniaturized while maintaining extremely high dimensional accuracy and processing accuracy by micromachining technology based on LSI manufacturing technology. In addition, mass production is possible. Therefore, development of micromachines using silicon has been actively conducted.

  In recent years, a technical field called MEMS (MicroElectro Mechanical System) technology has been created, and in addition to the application fields described in Non-Patent Document 1, the present invention is also applied to various fields such as sensors, medical care, optical communication, and wireless communication. Applications are spreading.

  Among these, a wide range of research and development has been undertaken for MEMS (called RFMEMS) that processes high-frequency signals such as radio signals (see Non-Patent Documents 2 and 3). There are many types of RFMEMS elements such as inductors, switches, variable capacitors, resonators, filters, transmission lines, antennas, and the like.

RFMEM switch consumes very little power during operation, high isolation when switching off (high-frequency signal separation between input and output terminals), low switching resistance when switching on, low distortion characteristics due to high linearity, etc. There are many advantages over conventional RF switches (see Non-Patent Document 4).
However, as pointed out in Non-Patent Document 4, since the RFMEMS switch has a mechanical movable part in the structure, it is necessary to seal the RFMEM switch with a high cleanliness such as in a rare gas or in a vacuum. There is. For this reason, RFMEMS has a manufacturing problem that the package cost is high and mass production is difficult.

  As an example of a conventional MEMS switch, a switch in which a movable part is supported and fixed at one place (see Patent Document 1) and a switch in which a movable part is supported and fixed at two or more places (see Patent Documents 2 and 3) )and so on. All the MEMS switches realize the switch operation by utilizing the fact that a flat movable electrode supported by a spring structure is attracted by an electrostatic force. Patent Document 1 describes only the switch structure, and does not describe a specific manufacturing method.

  Patent Document 2 describes that a switch structure is manufactured on a substrate on which an electrical pattern such as a signal line is manufactured by a micromachine technique using an integrated circuit technique. Patent Document 3 describes a technique for manufacturing a switch structure by bonding a structure in which a movable part is manufactured to a substrate on which an electrical pattern such as a signal line is manufactured. In these prior arts, no consideration is given to the method of sealing the switch.

In a conventional MEMS switch sealing method, individual switch elements are cut out from a silicon wafer and then sealed for each element, and individual switch elements are sealed after the switch elements are collectively sealed in a silicon wafer state. There is a way to cut out.
As the former method of sealing each element, there is a method of mounting a MEMS switch on a package by a method similar to a known hermetic seal (hermetic seal). In this technique, there is a risk that the movable part may be damaged due to vibration applied to the switch movable part in a process of cutting out the element for mounting after the MEMS element is manufactured on the wafer and handling of the cut out element.

  In the mounting process of the MEMS switch, careful handling is necessary so that the fine movable part is not damaged. Further, in the inspection process after mounting the MEMS switch, it is necessary to guarantee the quality of each switch element. Therefore, in the prior art, the size of parts inevitably increases, and it is difficult to apply to mass production.

  Next, a description will be given of the prior art of the method of collectively sealing the latter wafer. For example, in order to package a SAW (Surface Acoustic Wave) resonator, a space is produced in a glass substrate, a SAW chip is built in the produced space, and finally two glass substrates are bonded together to form a SAW chip. Has been proposed (see Non-Patent Document 5).

  In addition, after manufacturing the MEMS element on the wafer, another substrate (sealing chip) for sealing is prepared, and BCB (benzocyclobutene) shaped so as to surround the periphery of the MEMS element on the sealing chip. ) A method of sealing by forming a frame pattern by a film and attaching a sealing chip to a wafer on which a MEMS element is manufactured by a flip chip has been proposed (see Non-Patent Document 6).

  In addition, a method has been proposed in which a MEMS element fabricated on a wafer is covered with a small cap that is slightly larger than the element size, and a material called LCP (Liquid Crystal Polymer) is deposited and solidified on the small cap for sealing. (See Non-Patent Document 7).

The applicant has not yet found prior art documents related to the present invention by the time of filing other than the prior art documents specified by the prior art document information described in this specification.
JP 2000-294104 A Japanese Patent Laid-Open No. 11-250792 JP 2001-266727 A KEPetersen, “Silicon as a mechanical materia1”, Proc. IEEE, Vol.70, No.5, pp.420-457, May 1982. RJRichards and HJDe Los Santos, "MEMS for RF / microwave wireless applications: the next wave", Microwave Journal, Vol.44, No.3, pp.20-41, Mar.2001. HJDe Los Santos and RJRichards, "MEMS for RF / microwave wireless applications: the next wave-PART II", Microwave Journal, Vol.44, No.7, pp.142-152, July 2001. GMRebeiz and JBMuldavin, “RF MEMS switches and switch circuits”, IEEE Microwave Magazine, Vol.2, No.4, pp.59-70, Dec.2001. D. Ando, K. Oishi, T. Nakamura, and S. Umeda, "Glass direct bonding technology for hermetic seal package", IEEE 10th Int. Wiorkshop on Micro Electro Mechanical Systems, pp. 186-190, Jan. 1997. A. Jourdain, P. De Moor, S. Pamidighantam, and ACTilmans, "Investigation of the hermeticity of BCB-sealed cavities for housing (RF-) MEMS devices", 15th IEEE Int. Conf. Micro Electro Mechanical Systems, pp. 677 -680, Jan. 2002. FFFaheem, KCGupta, and Y.-C.Lee, "Flip-chip assembly and liquid crystal polymer encapsulation for variable MEMS capacitors", IEEE Trans. Microwave Theory and Tech., Vol.51, No.12, pp.2562-2567 , Dec. 2003. SPPacheco, LPBKatehi, and CT-C. Nguyen, "Design of low actuation voltage RFMEMS switch", 2000 IEEE MTT-S Int. Microwave Symp., Vol.1, pp.165-168, June 2000. N.Sato, H.Ishii, S.Shigematu, H.Morimura, T.Kamei, K.Kudou, M.Yano, K.Machida, H.Kyuragi, "A sealing technique for stacking MEMS on LSI using spin-coating film transfer and hot pressing ", Jpn.J.App1.Phys., Vol.42, Part 1, No.4B, pp.2462-2467, Apr.2003.

  However, in any of the above-described techniques, a special dedicated process is required to seal the MEMS element, and it is very difficult to reduce the manufacturing cost of the MEMS element including the mounting. Furthermore, since the sealing method is special and not universal, it is difficult to greatly change the structure of the MEMS switch, and it is possible to manufacture and mount MEMS switches having different structures and sizes on the same chip. It was difficult.

  The present invention has been made to solve the above-described problems. Elements in different forms composed of fine structures such as MEMS elements are mounted on a semiconductor substrate on which an LSI or the like is formed. The purpose is to enable monolithic mounting.

The method for manufacturing an electrostatic drive switch according to the present invention includes a step of forming a side wall frame on a semiconductor substrate so as to surround a predetermined region, and a step of forming an element on the semiconductor substrate inside the side wall frame. And a step of forming a ceiling wall facing the surface of the semiconductor substrate on the side wall frame so that the element is sealed in a container composed of the side wall frame and the ceiling wall. A movable body supported above the semiconductor substrate via a spring beam, a contact electrode disposed on the lower surface of the movable body on the semiconductor substrate side, and a signal line disposed below the movable body, The drive element is disposed under the movable body and attracts the movable body by electrostatic force, and is a switch element based on an electrical conduction state between the contact electrode and the signal line.

  In the manufacturing method of the electrostatic drive switch, a first step in which the first seed layer is formed on the semiconductor substrate, and a state in which the first metal pattern is formed on the first seed layer by plating. After that, a second step in which the seed layer is selectively removed by etching using the first metal pattern as a mask, and an interlayer insulating film is formed on the semiconductor substrate so as to cover the first metal pattern A third step of forming a state, a fourth step of forming a contact hole at a desired position of the interlayer insulating film corresponding to a partial region of the first metal pattern, and an interlayer insulating film including the inside of the contact hole After the fifth step in which the second seed layer is formed on the second seed layer and the second metal pattern and the thicker third metal pattern formed on the second seed layer by plating. A sixth process in which the second seed layer is selectively removed by etching using the second metal pattern and the third metal pattern as a mask, and the second metal pattern is covered by filling the space between the third metal patterns. After the photosensitive organic resin film is formed on the interlayer insulating film, the photosensitive organic resin film is patterned by exposure and development, and the interlayer insulating is performed with a part of the third metal pattern exposed. A seventh step in which the first sacrificial layer is formed on the film; and a seventh step in which the third seed layer is formed on the first sacrificial layer including the exposed portion of the third metal pattern. After the contact electrode and the fourth metal pattern are formed on the third seed layer by eight steps and plating, the third seed layer is formed by etching using the contact electrode and the fourth metal pattern as a mask. Selectively removed The ninth step, and the contact electrode and the fourth metal pattern are embedded to form a photosensitive organic resin film on the first sacrificial layer, and then the photosensitive organic resin is exposed and developed. A tenth step of patterning the film to form a second sacrificial layer on the first sacrificial layer with the contact electrode and a portion of the fourth metal pattern exposed, and a second sacrificial including the contact electrode An eleventh step in which the first inorganic insulating layer is formed in a predetermined region on the layer; and a fourth seed layer is formed on the second sacrificial layer so as to cover the first inorganic insulating layer. After the twelfth step and the fifth metal pattern are formed on the fourth seed layer by plating, the fourth seed layer is selected by etching using the first inorganic insulating layer and the fifth metal pattern as a mask. The 13th step to be removed and the first inorganic After filling the space between the insulating layer and the fifth metal pattern to form a photosensitive organic resin film on the second sacrificial layer, the photosensitive organic resin film is patterned by exposure and development, and the first inorganic insulation is formed. A fourteenth step in which a third sacrificial layer is formed on the second sacrificial layer in a state where a part of the layer and the fifth metal pattern are exposed, and the exposed first inorganic insulating layer and the fifth metal pattern The fifth metal layer and the seventh metal pattern thicker than the fifteenth step, in which the fifth seed layer is formed on the third sacrificial layer including the portion, and the plating method, After the state formed above, the sixteenth step in which the fifth seed layer is selectively removed by etching using the sixth metal pattern and the seventh metal pattern as a mask, and the first inorganic insulating layer Of the sixth metal pattern that hits the top After the 17th step in which the second inorganic insulating layer is formed in the predetermined region, and between the seventh metal pattern and the photosensitive organic resin film is formed on the third sacrificial layer Then, the photosensitive organic resin film is patterned by exposure and development, and the eighteenth step is performed in which a fourth sacrificial layer is formed on the third sacrificial layer with a part of the seventh metal pattern exposed. A nineteenth step in which the sixth seed layer is formed on the fourth sacrificial layer including the seventh metal pattern portion, and an eighth metal pattern having a plurality of openings is formed by the sixth seed by plating. And a 20th step in which the sixth seed layer is selectively removed by etching using the eighth metal pattern as a mask, and an opening of the eighth metal pattern. By etching, the first sacrificial layer and the second sacrificial layer A twenty-first step in which the layer, the third sacrificial layer, and the fourth sacrificial layer are removed; and a twenty-second step in which an insulating film is formed on the eighth metal pattern so as to close the opening. The third metal pattern is composed of a frame-shaped part surrounding the region where the first metal pattern is formed, and a part arranged inside the frame-shaped part, and the sixth metal pattern is You may make it form over the part arrange | positioned inside.

  In the method of manufacturing an electrostatic drive switch, the first metal layer is formed on the first seed layer by a first step of forming a first seed layer on the semiconductor substrate and a plating method. After the second state, the second step in which the seed layer is selectively removed by etching using the first metal pattern as a mask, and the interlayer insulating film is formed on the semiconductor substrate so as to cover the first metal pattern A third step in which the contact hole is formed, a fourth step in which the contact hole is opened at a desired position of the interlayer insulating film corresponding to a partial region of the first metal pattern, and interlayer insulation including the inside of the contact hole A fifth step in which a second seed layer is formed on the film, and a plating method that is disposed in a region including the second metal pattern and the upper portion of the first metal pattern and is thicker than the second metal pattern. After the third metal pattern is formed on the second seed layer, the second seed layer is selectively removed by etching using the second metal pattern and the third metal pattern as a mask. A photosensitive organic resin film is formed on the interlayer insulating film in a state in which the second metal pattern is covered by filling the space between the sixth step and the third metal pattern, and then exposed to light by exposure and development. Patterning the organic resin film to form a first sacrificial layer on the interlayer insulating film in a state in which a part of the third metal pattern is exposed; and a portion of the exposed third metal pattern In addition, an eighth step in which a third seed layer is formed on the first sacrificial layer, and a fourth metal pattern disposed on the contact electrode and the third metal pattern by the plating method, Form formed on seed layer After that, a ninth step of selectively removing the third seed layer by etching using the contact electrode and the fourth metal pattern as a mask, and filling between the contact electrode and the fourth metal pattern, After the photosensitive organic resin film is formed on the first sacrificial layer, the photosensitive organic resin film is patterned by exposure and development, and the first sacrificial film is exposed with a part of the contact electrode and the fourth metal pattern exposed. A tenth step in which the second sacrificial layer is formed on the layer, and an eleventh step in which the first inorganic insulating layer is formed in a predetermined region on the second sacrificial layer including the contact electrode; A twelfth step of covering the first inorganic insulating layer and forming a fourth seed layer on the second sacrificial layer; and a fifth metal pattern disposed on the fourth metal pattern, It is formed on the seed layer by plating. Then, between the first inorganic insulating layer and the fifth metal pattern, the thirteenth step in which the fourth seed layer is selectively removed by etching using the first inorganic insulating layer and the fifth metal pattern as a mask. Is embedded to form a photosensitive organic resin film on the second sacrificial layer, and then the photosensitive organic resin film is patterned by exposure and development to form a part of the first inorganic insulating layer and the fifth metal pattern. A 14th step of forming a third sacrificial layer on the second sacrificial layer with the exposed portion of the third sacrificial layer including the exposed first inorganic insulating layer and the fifth metal pattern portion; The sixth metal pattern disposed on the region including the upper part of the fifth metal pattern is formed on the fifth seed layer by the fifteenth step in which the fifth seed layer is formed on the upper surface and the plating method. After the formed state, the sixth metal pattern is A 16th step in which the fifth seed layer is selectively removed by etching that forms a mask, and a second inorganic insulating layer is formed in a predetermined region on the sixth metal pattern that hits the top of the first inorganic insulating layer. A seventeenth step in which the sixth seed layer is formed on the third sacrificial layer including the second inorganic insulating layer and the sixth metal pattern, and a plating method. Then, after the seventh metal pattern disposed on the fifth metal pattern is formed on the sixth seed layer, the sixth seed layer is selectively formed by etching using the seventh metal pattern as a mask. A state in which the photosensitive organic resin film is formed on the third sacrificial layer in a state in which the second inorganic insulating layer is covered by filling the space between the seventh metal pattern and the nineteenth step to be removed After exposure to photosensitive organic Patterning the oil film to form a fourth sacrificial layer on the third sacrificial layer with a portion of the seventh metal pattern exposed; and exposing the exposed portion of the seventh metal pattern. An eighth metal pattern having a plurality of openings is formed on the seventh seed layer by a twenty-first process in which the seventh seed layer is formed on the fourth sacrificial layer including the plating and a plating method. Then, the first sacrificial layer is formed by etching through the opening of the eighth metal pattern and the twenty-second process in which the seventh seed layer is selectively removed by etching using the eighth metal pattern as a mask. , A 23rd step in which the second sacrificial layer, the third sacrificial layer, and the fourth sacrificial layer are removed, and a state in which an insulating film is formed on the eighth metal pattern so as to close the opening. 24th process at least, and a 3rd metal putter The first metal pattern may be formed in a frame shape surrounding the region where the first metal pattern is formed, and the sixth metal pattern may be formed over a portion where the third metal pattern is disposed.

  As described above, in the present invention, a semiconductor substrate is provided by a container including a ceiling wall facing the surface of the semiconductor substrate formed on the semiconductor substrate and a side wall frame that supports the ceiling wall on the semiconductor substrate. The switch element formed on is sealed. As a result, according to the present invention, different types of elements composed of fine structures such as MEMS elements are monolithically formed on a semiconductor substrate on which LSIs are formed, for example, by a consistent manufacturing process. The excellent effect of being able to be mounted on is obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a plan view (a) and a sectional view (b) showing a configuration example of an electrostatic drive switch according to an embodiment of the present invention. The electrostatic drive switch shown in FIG. 1 includes an interlayer insulating layer 102 on a semiconductor substrate 101 such as silicon, and the insulating plate formed on both surfaces of the plate movable electrode 105 and the plate movable electrode 105 on the interlayer insulating layer 102. Layer 106 is provided.

  The electrostatic drive switch shown in FIG. 1 is fixed to the lower surface of the movable plate electrode 105 and the spring beam 107 connected to the side of the movable plate electrode 105, the anchor 108 for fixing the spring beam 107 on the interlayer insulating layer 102, and the lower surface of the movable plate electrode 105. The switch structure includes a contact electrode 109, a drive electrode portion 110, and a signal wiring portion 111 disposed on the interlayer insulating layer 102. The plate movable electrode 105 is connected to the upper part of the anchor 108 by a spring beam 107 and can be displaced in the normal direction of the plane of the semiconductor substrate 101.

  In addition, the electrostatic drive switch shown in FIG. 1 includes a side wall frame 103 so as to surround the switch structure. Further, a ceiling wall 104 is provided on the side wall frame 103, and a container that surrounds the switch structure is constituted by these. The side wall frame 103 and the ceiling wall 104 are made of, for example, a metal material. The side wall 103 and the ceiling wall 104 may be made of a material such as silicon oxide or silicon nitride. In FIG. 1A, the ceiling wall 104 is not shown in order to make the planar structure of the switch easier to see.

  In the electrostatic drive switch shown in FIG. 1, the switch structure can be sealed in an inert gas atmosphere such as a rare gas or in a vacuum by a container including the side wall frame 103 and the ceiling wall 104. The influence of noise and unnecessary radiation to the outside can be shielded. Note that the side wall frame 103 has a rectangular planar shape, but is not limited thereto, and may be a polygon such as a triangle or a hexagon, or may be a polygon including a convex portion or a concave portion. In particular, in the case of a rectangle, a triangle, or a hexagon, a plurality of containers (side wall frames 103) can be arranged on the same plane without gaps.

  Next, the operation of the switch structure inside the container will be described. The electrostatic drive switch shown in FIG. 1 applies the voltage Vsw between the flat plate movable electrode 105 and the drive electrode 110 to attract the flat plate movable electrode 105 to the drive electrode 110 by electrostatic force, and the contact electrode 109 and the signal line. The switch operation is performed when 111 comes into contact. Vsw at this time can be obtained as a pull-in voltage of a parallel plate and can be expressed by the following equation (1).

  In the above equation (1), k is the spring constant of the spring beam 107, d is the gap between the flat plate movable electrode 105 and the drive electrode unit 110, ε is the dielectric constant of the gap, and S is the area of the flat plate movable electrode 105. .

  Next, in the electrostatic drive switch shown in FIG. 1, it is first considered to obtain a spring constant for one spring beam 107 by calculation. As a calculation example, the spring constant is calculated when a meandering spring beam having the dimensions shown in FIG. 2 is elastically deformed by fixing one end and applying a vertical force to the other end of the paper. To do. A calculation formula for obtaining the spring constant k in such a structure is shown in Non-Patent Document 8, and can be obtained by the following equation (2).

  In the above equation (2), N is the number of meandering spring beams, w is the width of the spring beam, t is the thickness of the spring beam, l is the length of the short side of the spring beam, and L is the length of the long side of the spring beam. Length, E is Young's modulus, and ν is Poisson's ratio.

  In the electrostatic drive switch shown in FIG. 1, since four spring beams with N = 2 are connected to the four corners of the plate movable electrode 105, the total spring constant k_total can be obtained by the following equation (3). it can.

Specifically, when the electrostatic drive switch shown in FIG. 1 is calculated, when the spring beam is gold having a thickness of 0.5 μm, E = 78 GPa and ν = 0.31, and the structural constant is w = When 5 μm, t = 0.5 μm, 1 = 10 μm, and L = 40 μm, the spring constant k_total = 1.48 N / m from Equation 3. With this spring structure, the pull-in voltage when the structure of the plate movable electrode 105 is d = 1.5 μm and S = 10000 μm ² is obtained from Equation 1 as Vsw = 4.1V.

  In the electrostatic drive switch shown in FIG. 1, the plate movable electrode 105 has a rectangular shape, and has a structure in which four spring beams 107 are connected to the four corners. Since the spring beams 107 are arranged at the four corners, a switch structure with less distortion can be obtained, and the movement of the flat plate movable electrode 105 in the horizontal direction during the switch operation can be suppressed. Furthermore, the spring beam 107 having a meandering structure makes it possible to realize a spring beam having a small spring constant with a small occupied area, thereby realizing a switch structure that operates with a low pull-in voltage.

  Further, as shown in FIG. 1B, the flat plate movable electrode 105 includes the insulating layers 106 on the upper and lower surfaces of the flat plate-shaped metal flat plate movable electrode 105, so that an excessive switch voltage is applied. Therefore, even if the plate movable electrode 105 moves up and down largely and comes into contact with other structures, problems such as electrode sticking and short-circuiting do not occur.

  Furthermore, warping of the plate movable electrode 105 can be prevented by making the movable electrode part a three-layer structure of insulating film / metal film / insulating film. In general, in a structure in which thin films made of different types of materials are bonded together, warpage is likely to occur because the internal stress of the thin film differs depending on the material. On the other hand, since the flat movable electrode 105 is sandwiched by the same insulating film 106, the effects of internal stress cancel each other, and the occurrence of warpage can be suppressed.

Next, another electrostatic drive switch of the present invention will be described.
FIG. 3 is a plan view (a) and a cross-sectional view (b) showing another configuration example of the electrostatic drive switch according to the embodiment of the invention. In the electrostatic drive switch shown in FIG. 3, the plate movable electrode 105 is connected to the inside of the side wall frame 103 by a spring beam 137 and can be displaced in the normal direction of the plane of the semiconductor substrate 101. The anchor 108 provided in the electrostatic drive switch shown in FIG. 1 is not necessary in the electrostatic drive switch shown in FIG. Other configurations are the same as those of the electrostatic drive switch shown in FIG.

  Since the electrostatic drive switch shown in FIG. 3 does not require an anchor as described above, an area for anchoring is not necessary, and the spring beam 137 having a higher number of meanders is used using this area. Is possible. By using a spring beam having a large number of meanders, the operating voltage of the switch can be lowered.

  With respect to the electrostatic drive switch of FIG. 3, when the operating voltage of the switch is calculated by Equations 1 and 3, Vsw = 2.9V. In the calculation results, the number of meanders is N = 4, and other structural constants are obtained from the same numerical values as those of the electrostatic drive switch shown in FIG. The simulation result of the drive voltage of the electrostatic drive switch of FIG. 1 is 4.1 V, but the drive voltage is lower according to the electrostatic drive switch of FIG.

  When there is no need to lower the operating voltage (driving voltage), the number of meandering of the spring beam can be reduced, the area of the side wall frame 103 can be narrowed by the anchor area, and the overall element size can be reduced.

Next, a method for manufacturing the above-described electrostatic drive switch will be described.
First, an example of a manufacturing method of the electrostatic drive switch shown in FIG. 1 will be described.
First, an interlayer insulating layer 102 made of, for example, silicon oxide is formed on a semiconductor substrate 101 made of, for example, silicon. The semiconductor substrate 101 may include a semiconductor integrated circuit composed of a plurality of transistors, resistors, capacitors, wirings, and the like. For example, a contact hole for electrical connection with the wiring of the integrated circuit has interlayer insulation. It may be formed at a predetermined location of the layer 102.

  When such a substrate is prepared, the first seed layer 203 is formed on the interlayer insulating layer 102 as shown in FIG. The first seed layer 203 may be formed by, for example, first depositing titanium and depositing gold thereon by sputtering or vapor deposition. The thickness of titanium may be about 0.1 μm, and the thickness of gold may be about 0.1 μm.

Next, a resist material is applied on the first seed layer 203 and exposed using a mask having a desired pattern to form a resist pattern having an opening at a desired location. A gold pattern is formed on the exposed first seed layer 203 by plating, and then the resist pattern is removed to form a first metal pattern 204 as shown in FIG. 4B. And
At this time, the resist film thickness is about 1 μm, and the plating film is formed to a film thickness of about 0.3 μm, whereby the thickness of the first metal pattern 204 can be formed to about 0.3 μm.

  Next, the first seed layer 203 is removed by etching using the first metal pattern 204 as a mask, so that the first metal pattern 204 is separated on the interlayer insulating layer 102 as shown in FIG. For example, gold on the upper layer of the first seed layer 203 may be wet-etched with an etching solution made of iodine, ammonium iodide, water, and ethanol. The titanium under the first seed layer 203 exposed by this etching can be wet-etched with an aqueous hydrogen fluoride solution.

Next, a silicon oxide film is deposited on the interlayer insulating layer 102 including the first metal pattern 204 by, for example, sputtering, and this film is used in FIG. As shown, an interlayer insulating film 205 having a thickness of about 1 μm is formed with the surface being flattened.
Next, as shown in FIG. 4E, a contact hole 206 is formed at a desired position of the interlayer insulating film 205 by a known lithography technique and etching technique.

  Next, as shown in FIG. 4F, the second seed layer 207 is formed on the interlayer insulating film 205 including the formed contact hole 206. The second seed layer 207 can be formed in the same manner as the first seed layer 203. Next, the second metal pattern 208 is formed in the same manner as the first metal pattern 204. Subsequently, by repeating the same process, the third metal pattern 209 is formed. The third metal pattern 209 is formed to be thicker than the second metal pattern 208.

For example, when the second metal pattern 208 is formed, the resist pattern serving as a mask may have a thickness of about 1 μm and the plating film may be formed in a thickness of about 0.3 μm. Further, when the third metal pattern 209 is formed, the thickness of the resist pattern serving as a mask may be about 1 μm, and the plating film may be formed to a thickness of about 0.8 μm.
Next, the seed layer 207 is removed by the same etching method as that for the first seed layer 203, so that the second metal pattern 208 and the third metal pattern 209 become the interlayer insulating film 205 as shown in FIG. Are separated from each other.

  Next, as shown in FIG. 5H, the first sacrificial layer 210 is formed on the interlayer insulating layer 102 with the second metal pattern 208 covered and the upper surface of the third metal pattern 209 exposed. It is assumed that For example, the first sacrificial layer 210 can be formed by applying a photosensitive organic resin made of PBO (polybenzoxazole) to form a coating film, and patterning the formed coating film by a known lithography technique.

  In the patterning process for forming the first sacrificial layer 210, pre-baking at 120 ° C. is performed for about 4 minutes as pre-processing, and heat processing at about 310 ° C. is performed after patterning, so that the organic resin film is thermally cured. . As the organic resin, CRC8300 manufactured by Sumitomo Bakelite Co., Ltd. can be used.

  Next, as shown in FIG. 5I, the third seed layer 211 is formed by the same process as the first seed layer 203, and the film is formed by the same process as the second metal pattern 208. The contact electrode 212 having a thickness of about 0.3 μm is formed, and the fourth metal pattern 213 having a thickness of about 0.3 μm is formed by the same manner as the third metal pattern 209. The fourth metal pattern 213 is formed in contact with the third metal pattern 209.

  Next, similarly to the method described with reference to FIG. 4C, the exposed region of the third seed layer 211 is removed by etching so that each pattern is separated. Note that different seed layers may be used for the contact electrode 212 and the fourth metal pattern 213. For example, the seed layer for forming the contact electrode 212 may be a multilayer film made of chromium and gold.

Subsequently, a second sacrificial layer 214 is formed as shown in FIG. 5J by forming a resin film made of polybenzoxazole so as to fill the side portions of the respective patterns. The second sacrificial layer 214 may be formed in the same manner as the first sacrificial layer 210.
Next, as shown in FIG. 5K, the titanium layer 215 is formed on the second sacrificial layer 214 by sputtering or the like, and the first inorganic insulating layer 216 is formed on the titanium layer 215. State. The first inorganic insulating layer 216 can be formed, for example, by processing a silicon oxide film deposited by a sputtering method using a known photolithography technique and etching technique. Note that the thickness of the titanium layer 215 may be about 0.1 μm, and the thickness of the first inorganic insulating layer 216 may be about 0.3 μm.

  Next, using the first inorganic insulating layer 216 as a mask, the titanium layer 215 is etched by wet etching using an aqueous hydrogen fluoride solution, and thereafter, the same as the formation of the first seed layer 203 and the formation of the first metal pattern 204. By doing so, as shown in FIG. 6L, the fourth seed layer 217 and the fifth metal pattern 218 are formed. Subsequently, the unnecessary seed layer 217 is selectively removed. As a result, the upper surface of the first inorganic insulating layer 216 is exposed. Note that the plating thickness of the fifth metal pattern 218 may be about 0.3 μm.

Next, in the same manner as the formation of the first sacrificial layer 210 and the second sacrificial layer 214, the third sacrificial layer 219 is formed as shown in FIG. The third sacrificial layer 219 is formed in a state where the top surfaces of the first inorganic insulating layer 216 and the fifth metal pattern 218 are exposed.
Next, as shown in FIG. 5 (n), a fifth seed layer 220 is formed on the top surfaces of the first inorganic insulating layer 216 and the fifth metal pattern 218 and the third sacrificial layer 219. The sixth metal pattern 221 and the seventh metal pattern 222 thicker than the sixth metal pattern 221 are formed by two plating steps.

Subsequently, the unnecessary seed layer 220 is selectively removed. At this time, the plating thickness of the sixth metal pattern 221 may be about 0.3 μm, and the plating thickness of the seventh metal pattern 222 may be about 1 μm.
Next, after the titanium layer 223 is deposited by the same method as described above, the second insulating layer 224 is formed as shown in FIG. 5 (o) by performing the same process as the first inorganic insulating layer 216. And The thickness of the titanium layer 223 may be about 0.1 μm, and the thickness of the second insulating layer 224 may be about 0.3 μm.

Next, the fourth sacrificial layer 225 is formed as shown in FIG. 7P by the same method as that for forming the sacrificial layers described above.
Subsequently, after the seed layer 226 is formed on the fourth sacrificial layer 225 by the same method as described above, the metal layer (eighth metal pattern) 227 is formed on the seed layer 226. In addition, an unnecessary seed layer 226 is removed using the formed metal layer 227 as a mask pattern (FIG. 7 (q)). The metal layer 227 includes one or more openings 228. For example, the metal layer 227 is provided so that a plurality of openings 228 are arranged in a lattice pattern. The metal pattern 227 may have a film thickness of about 1 μm.

  Next, ozone is applied to the first sacrificial layer 210, the second sacrificial layer 214, the third sacrificial layer 219, and the fourth sacrificial layer 225 from the opening 228 of the metal layer 227 using, for example, an ozone asher device, and the first sacrificial layer 225. By removing the layer 210, the second sacrificial layer 214, the third sacrificial layer 219, and the fourth sacrificial layer 225, a space is formed below the metal layer 227 as shown in FIG. . Thereafter, the insulating film 229 is attached to the upper surface of the metal layer 227 by STP (spin-coating film transfer and hot pressing: see Non-Patent Document 9) method. The ceiling wall 104 is configured by the metal layer 227 and the insulating film 229.

  The insulating film 229 may be made of an organic material having a thickness of about 5 μm, for example. Note that the insulating film 229 may be formed by another method. For example, it may be formed by applying a resin, or may be formed by depositing an insulating film by chemical vapor deposition. Alternatively, a conductive film such as a metal may be disposed on the metal layer 227 instead of the insulating film 229 so as to close the opening 228 of the metal layer 227.

Next, an example of a manufacturing method of the electrostatic drive switch shown in FIG. 3 will be described.
First, in the same manner as the above-described steps from FIG. 4A to FIG. 6M, the interlayer insulating layer 102 is formed on the semiconductor substrate 101 as shown in FIG. Layer 303, first metal pattern 304, interlayer insulating film 305, second seed layer 307, second metal pattern 308, third metal pattern 309, first sacrificial layer 310, third seed layer 311, contact electrode 312, fourth The metal pattern 313, the second sacrificial layer 314, the titanium layer 315, the first inorganic insulating layer 316, the fourth seed layer 317, the fifth metal pattern 318, and the third sacrificial layer 319 are formed.

  In addition, compared with the state shown in FIG. 6M, there is no columnar structure serving as an anchor in the process shown in FIG. In addition, a part of the side wall structure is connected to the first metal pattern 304 in order to fix the potential of the portion serving as the side wall.

  As described above, after the third sacrificial layer 319 is formed, the fifth seed layer 320 is formed as shown in FIG. 8B, and the fifth seed layer 320 is formed. A sixth metal pattern 321 is formed on the substrate. Here, the sixth metal pattern 321 includes the flat plate movable electrode 105, a portion to be a spring beam 137 having a spring structure, a connection portion between the spring beam 137 and the side wall frame 103, and the like shown in FIG. The plating thickness of the sixth metal pattern 321 may be about 0.3 μm. Subsequently, the unnecessary seed layer 320 is selectively removed.

  Next, as shown in FIG. 8C, the second insulating layer 323 is formed on the sixth metal pattern 321 via the titanium layer 322. For example, first, a titanium layer 321 is formed on the sixth metal pattern 321, and a silicon oxide film is deposited on the titanium layer 321 by sputtering or the like. Thereafter, a state in which the second insulating layer 323 is formed is obtained by processing the deposited silicon oxide film by a known photolithography technique and etching technique. Note that the thickness of the titanium layer 321 may be about 0.1 μm, and the thickness of the second insulating layer 323 may be about 0.3 μm.

  Subsequently, a sixth seed layer 324 is formed, a seventh metal pattern 325 is formed thereon, and the unnecessary sixth seed layer 324 is selectively removed using this as a mask. The plating thickness of the seventh metal pattern 325 may be about 0.6 μm. As described above, the fourth sacrificial layer 326 having an opening at a desired location is formed by lithography as described above, so that the seventh metal pattern 325 is formed as shown in FIG. A state is obtained in which the fourth sacrificial layer 326 is formed so as to fill the gap and cover the second insulating layer 323.

  Next, a seed layer (seventh seed layer) is formed on the fourth sacrificial layer 326 by, for example, first depositing titanium and depositing gold thereon by sputtering or vapor deposition. And The thickness of titanium may be about 0.1 μm, and the thickness of gold may be about 0.1 μm. Subsequently, a metal layer 327 having a plurality of openings 328 is formed on the seed layer, and an unnecessary seed layer is removed using the formed metal layer 327 as a mask pattern. .

  As described above, as shown in FIG. 9E, a state in which the metal layer 327 having a plurality of openings 328 is formed can be obtained. Thereafter, each sacrificial layer below the metal layer 327 is removed by, for example, an ozone asher, and the insulating film 329 is attached to the upper surface of the metal layer 327 by the STP method as shown in FIG. To do. The ceiling wall 104 is configured by the metal layer 327 and the insulating film 329.

  The insulating film 329 may be made of an organic material having a thickness of about 5 μm, for example. Note that the insulating film 329 may be formed by another method. For example, it may be formed by applying a resin, or may be formed by depositing an insulating film by chemical vapor deposition. Alternatively, a conductive film such as a metal may be provided over the metal layer 327 instead of the insulating film 329 so that the opening 328 of the metal layer 327 is blocked.

  By the above manufacturing method, the flat plate movable electrode 105, the spring beam 137 connected to the flat plate movable electrode 105, the contact electrode 109 formed by sandwiching the insulating film between the flat plate movable electrode 105, and the semiconductor substrate 101 are fixed. A mechanical switch structure including the drive electrode unit 110 and the signal wiring unit 111 disposed on the semiconductor substrate 101, and a structure in which the switch structure is sealed in a container including the ceiling wall 104 and the side wall frame 103. can get.

  Further, according to the manufacturing method described above, a MEMS switch can be manufactured and sealed as a subsequent step of a known semiconductor integrated circuit manufacturing process, and the semiconductor integrated circuit and the MEMS switch are integrated. With respect to the device, it is possible to manufacture a semiconductor integrated circuit, a MEMS switch, and a MEMS switch by a consistent manufacturing process.

It is the top view (a) and sectional drawing (b) which show the structural example of the electrostatic drive switch in embodiment of this invention. It is a top view which shows the structural example of a spring beam. It is the top view (a) and sectional drawing (b) which show the other structural example of the electrostatic drive switch in embodiment of invention. It is process drawing which shows the example of a manufacturing method of the electrostatic drive switch shown in FIG. It is process drawing which shows the example of a manufacturing method of the electrostatic drive switch shown in FIG. It is process drawing which shows the example of a manufacturing method of the electrostatic drive switch shown in FIG. It is process drawing which shows the example of a manufacturing method of the electrostatic drive switch shown in FIG. It is process drawing which shows the example of a manufacturing method of the electrostatic drive switch shown in FIG. It is process drawing which shows the example of a manufacturing method of the electrostatic drive switch shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Semiconductor substrate, 102 ... Interlayer insulating layer, 103 ... Side wall frame, 104 ... Ceiling wall, 105 ... Flat plate movable electrode, 106 ... Insulating layer, 107 ... Spring beam, 108 ... Anchor, 109 ... Contact electrode, 110 ... Driving electrode Part 111... Signal wiring part.

Claims (2)

A step of forming a side wall frame on the semiconductor substrate so as to surround the predetermined region;
Forming an element on the semiconductor substrate inside the side wall frame;
A ceiling wall facing the surface of the semiconductor substrate is formed on the side wall frame, and the element is sealed in a container composed of the side wall frame and the ceiling wall.
The element is
A movable body supported with a space above the semiconductor substrate via a spring beam in a support portion;
A contact electrode disposed on the lower surface of the movable body on the semiconductor substrate side;
A signal line disposed under the movable body;
A driving electrode disposed under the movable body and attracting the movable body by electrostatic force;
A switch element according to an electrical conduction state between the contact electrode and the signal line;
A first step in which a first seed layer is formed on the semiconductor substrate;
After the first metal pattern is formed on the first seed layer by plating, the seed layer is selectively removed by etching using the first metal pattern as a mask. Process,
A third step in which an interlayer insulating film is formed on the semiconductor substrate so as to cover the first metal pattern;
A fourth step in which a contact hole is opened at a desired position of the interlayer insulating film corresponding to a partial region of the first metal pattern;
A fifth step in which a second seed layer is formed on the interlayer insulating film including the inside of the contact hole;
Etching using the second metal pattern and the third metal pattern as a mask after the second metal pattern and the third metal pattern thicker than the second metal pattern are formed on the second seed layer by plating. A sixth step of selectively removing the second seed layer by:
A photosensitive organic resin film is formed on the interlayer insulating film in a state where the space between the third metal patterns is filled and the second metal pattern is covered, and then the photosensitive organic resin is exposed and developed. A seventh step of patterning a resin film, wherein a first sacrificial layer is formed on the interlayer insulating film with a portion of the third metal pattern exposed;
An eighth step in which a third seed layer is formed on the first sacrificial layer including the exposed portion of the third metal pattern;
After the contact electrode and the fourth metal pattern are formed on the third seed layer by plating, the third seed layer is formed by etching using the contact electrode and the fourth metal pattern as a mask. A ninth step of selectively removing,
After filling the space between the contact electrode and the fourth metal pattern and forming a photosensitive organic resin film on the first sacrificial layer, patterning the photosensitive organic resin film by exposure and development, A tenth step in which a second sacrificial layer is formed on the first sacrificial layer with the contact electrode and a portion of the fourth metal pattern exposed;
An eleventh step in which a first inorganic insulating layer is formed in a predetermined region on the second sacrificial layer including the contact electrode;
A twelfth step of covering the first inorganic insulating layer and forming a fourth seed layer on the second sacrificial layer;
After the fifth metal pattern is formed on the fourth seed layer by plating, the fourth seed layer is selectively formed by etching using the first inorganic insulating layer and the fifth metal pattern as a mask. And a thirteenth step for removing the
A space between the first inorganic insulating layer and the fifth metal pattern is embedded to form a photosensitive organic resin film on the second sacrificial layer, and then the photosensitive organic resin film is exposed and developed. A 14th step of patterning, wherein a third sacrificial layer is formed on the second sacrificial layer with a portion of the first inorganic insulating layer and the fifth metal pattern exposed;
A fifteenth step in which a fifth seed layer is formed on the third sacrificial layer including the exposed portions of the first inorganic insulating layer and the fifth metal pattern;
Etching using the sixth metal pattern and the seventh metal pattern as a mask after the sixth metal pattern and the seventh metal pattern thicker than the sixth metal pattern are formed on the fifth seed layer by plating. A sixteenth step in which the fifth seed layer is selectively removed by
A seventeenth step in which a second inorganic insulating layer is formed in a predetermined region on the sixth metal pattern that hits the top of the first inorganic insulating layer;
After filling the space between the seventh metal patterns to form a photosensitive organic resin film on the third sacrificial layer, the photosensitive organic resin film is patterned by exposure and development, and the seventh metal pattern is formed. An eighteenth step in which a fourth sacrificial layer is formed on the third sacrificial layer with a part of
A nineteenth step in which a sixth seed layer is formed on the fourth sacrificial layer including the exposed portion of the seventh metal pattern;
After the eighth metal pattern having a plurality of openings is formed on the sixth seed layer by plating, the sixth seed layer is selectively etched by etching using the eighth metal pattern as a mask. And a twentieth step for removing the
A twenty-first step in which the first sacrificial layer, the second sacrificial layer, the third sacrificial layer, and the fourth sacrificial layer are removed by etching through the opening of the eighth metal pattern;
And at least a twenty-second step in which an insulating film is formed on the eighth metal pattern so as to close the opening.
The third metal pattern is
A frame-shaped portion surrounding the region where the first metal pattern is formed, and a portion disposed inside the frame-shaped portion;
The sixth metal pattern is formed over a portion disposed on the inner side. The method of manufacturing an electrostatic drive switch, wherein: A step of forming a side wall frame on the semiconductor substrate so as to surround the predetermined region;
Forming an element on the semiconductor substrate inside the side wall frame;
A ceiling wall facing the surface of the semiconductor substrate is formed on the side wall frame, and the element is sealed in a container composed of the side wall frame and the ceiling wall.
The element is
A movable body supported with a space above the semiconductor substrate via a spring beam in a support portion;
A contact electrode disposed on the lower surface of the movable body on the semiconductor substrate side;
A signal line disposed under the movable body;
A driving electrode disposed under the movable body and attracting the movable body by electrostatic force;
A switch element according to an electrical conduction state between the contact electrode and the signal line;
A first step in which a first seed layer is formed on the semiconductor substrate;
After the first metal pattern is formed on the first seed layer by plating, the seed layer is selectively removed by etching using the first metal pattern as a mask. Process,
A third step in which an interlayer insulating film is formed on the semiconductor substrate so as to cover the first metal pattern;
A fourth step in which a contact hole is opened at a desired position of the interlayer insulating film corresponding to a partial region of the first metal pattern;
A fifth step in which a second seed layer is formed on the interlayer insulating film including the inside of the contact hole;
A third metal pattern that is disposed in a region including the second metal pattern and the upper portion of the first metal pattern and is thicker than the second metal pattern is formed on the second seed layer by plating. And a sixth step of selectively removing the second seed layer by etching using the second metal pattern and the third metal pattern as a mask;
A photosensitive organic resin film is formed on the interlayer insulating film in a state where the space between the third metal patterns is filled and the second metal pattern is covered, and then the photosensitive organic resin is exposed and developed. A seventh step of patterning a resin film, wherein a first sacrificial layer is formed on the interlayer insulating film with a portion of the third metal pattern exposed;
An eighth step in which a third seed layer is formed on the first sacrificial layer including the exposed portion of the third metal pattern;
After the contact electrode and the fourth metal pattern disposed on the third metal pattern are formed on the third seed layer by plating, the contact electrode and the fourth metal pattern are formed. A ninth step in which the third seed layer is selectively removed by etching using a mask;
After filling the space between the contact electrode and the fourth metal pattern and forming a photosensitive organic resin film on the first sacrificial layer, patterning the photosensitive organic resin film by exposure and development, A tenth step in which a second sacrificial layer is formed on the first sacrificial layer with the contact electrode and a portion of the fourth metal pattern exposed;
An eleventh step in which a first inorganic insulating layer is formed in a predetermined region on the second sacrificial layer including the contact electrode;
A twelfth step of covering the first inorganic insulating layer and forming a fourth seed layer on the second sacrificial layer;
After the fifth metal pattern disposed on the fourth metal pattern is formed on the fourth seed layer by plating, the first inorganic insulating layer and the fifth metal pattern are masked. A thirteenth step in which the fourth seed layer is selectively removed by etching
A space between the first inorganic insulating layer and the fifth metal pattern is embedded to form a photosensitive organic resin film on the second sacrificial layer, and then the photosensitive organic resin film is exposed and developed. A 14th step of patterning, wherein a third sacrificial layer is formed on the second sacrificial layer with a portion of the first inorganic insulating layer and the fifth metal pattern exposed;
A fifteenth step in which a fifth seed layer is formed on the third sacrificial layer including the exposed portions of the first inorganic insulating layer and the fifth metal pattern;
After the sixth metal pattern disposed on the region including the upper portion of the fifth metal pattern is formed on the fifth seed layer by plating, the sixth metal pattern is used as a mask. A sixteenth step in which the fifth seed layer is selectively removed by the etched step;
A seventeenth step in which a second inorganic insulating layer is formed in a predetermined region on the sixth metal pattern that hits the top of the first inorganic insulating layer;
An eighteenth step in which a sixth seed layer is formed on the third sacrificial layer including the second inorganic insulating layer and the sixth metal pattern;
After the seventh metal pattern disposed on the fifth metal pattern is formed on the sixth seed layer by plating, the first metal pattern is etched by using the seventh metal pattern as a mask. A nineteenth step in which the six seed layers are selectively removed;
A photosensitive organic resin film is formed on the third sacrificial layer so that the second inorganic insulating layer is covered with the space between the seventh metal patterns, and then the photosensitive organic resin film is exposed and developed. A 20th step of patterning a conductive organic resin film, wherein a fourth sacrificial layer is formed on the third sacrificial layer in a state where a part of the seventh metal pattern is exposed;
A twenty-first step in which a seventh seed layer is formed on the fourth sacrificial layer including the exposed portion of the seventh metal pattern;
After the eighth metal pattern having a plurality of openings is formed on the seventh seed layer by plating, the seventh seed layer is selectively formed by etching using the eighth metal pattern as a mask. The 22nd step to be in a removed state;
A 23rd step of removing the first sacrificial layer, the second sacrificial layer, the third sacrificial layer, and the fourth sacrificial layer by etching through the opening of the eighth metal pattern;
And at least a twenty-fourth step in which an insulating film is formed on the eighth metal pattern so as to close the opening.
The third metal pattern is
Formed in a frame shape surrounding the region where the first metal pattern is formed,
The sixth metal pattern is formed over a portion where the third metal pattern is disposed. A method of manufacturing an electrostatic drive switch, wherein:

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