JP2009252672A - Method for manufacturing switching element and switching element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing switching element easy to control air gap formation between a contact electrode pair and suited for alleviating contact resistance. <P>SOLUTION: The method, for manufacturing a switching element having a contact electrode pair for contacting each other, includes a process of forming a sacrifice layer 107 covering a contact electrode 13 on a substrate 101, a process of forming an opening through which the contact electrode 13 is partially exposed by patterning the sacrifice layer 107, a process of forming a seed layer 108 at least consisting of two layers 108a, 108b over a point exposed in the above process and the sacrifice layer 107, a process of forming the contact electrodes 14 opposed to the contact electrode 13 through the sacrifice layer 107, and equipped with a site containing a protrusion 14a filling the opening, a process of removing the sacrifice layer 107, and a process of removing at least a lowermost layer 108a of the seed layer 108 in the protrusion 14a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a switching element manufacturing method using MEMS technology, a switching element, and various apparatuses including the switching element.

  In the technical field of wireless communication devices such as mobile phones, there is an increasing demand for downsizing of RF circuits as the number of components mounted to realize high functions increases. In order to meet such demands, various parts constituting a circuit are being miniaturized by utilizing MEMS (micro-electromechanical systems) technology.

  A MEMS switch is known as one of such components. The MEMS switch is a switching element in which each part is minutely formed by the MEMS technology, and at least a pair of contacts for performing switching by mechanically opening and closing and a mechanical opening and closing operation of the contact pair are achieved. Drive mechanism. MEMS switches tend to exhibit higher isolation in the open state and lower insertion loss in the closed state than switching elements such as PIN diodes and MESFETs, particularly in switching high-frequency signals on the order of GHz. This is due to the fact that the open state is achieved by mechanical separation between the contact pairs and that the parasitic capacitance is low because of the mechanical switch. The MEMS switch is described in, for example, Patent Documents 1 to 4 below.

Japanese Patent Laid-Open No. 2004-1186 JP 2004-311394 A JP 2005-293918 A JP 2005-528751 gazette

  FIG. 39 shows a partial structure of a conventional switching element X3 which is a MEMS switch. The switching element X3 includes a contact electrode 92 provided on the base material 91, and a contact electrode 93 having a portion facing the contact electrode 92. The contact electrode 93 has a protrusion 93 a extending toward the contact electrode 92. The contact electrodes 92 and 93 are provided so as to be able to approach and separate, and the contact between the contact electrode 92 and the protrusion 93a of the contact electrode 93 brings the switching element X3 into a closed state so that the contact electrode 92 and 93 are in contact with each other. Current or high-frequency signals can pass through.

  FIG. 40 illustrates a part of the process in the method for manufacturing the switching element X3. FIG. 41 shows an enlarged view of the process in the vicinity of the protrusion forming portion in this manufacturing method.

  In manufacturing the switching element X3, first, as shown in FIG. 40A, the contact electrode 92 is formed on the base material 91. As shown in FIG. Next, as shown in FIG. 40B, a sacrificial layer 94 is formed on the base material 91 so as to cover the contact electrode 92. Next, as shown in FIGS. 40C and 41A, a recess 94a is formed at a position corresponding to the contact electrode 92 in the sacrificial layer 94 by so-called half etching. The recess 94 a is for forming the protrusion 93 a of the contact electrode 93. In this step, after a predetermined resist pattern is formed on the sacrificial layer 94, the sacrificial layer 94 is etched halfway in the thickness direction using the resist pattern as a mask.

  Next, as shown in FIG. 41B, an energization seed layer 95 (not shown in FIG. 40) used when the electroplating method is performed is formed on the surface of the sacrificial layer 94.

  Next, after a resist pattern having a predetermined opening is formed on the sacrificial layer 94, the protrusion 93a is formed in the opening of the resist pattern as shown in FIGS. 40 (d) and 41 (c). A contact electrode 93 is formed. Specifically, for example, Au is grown by electroplating on the seed layer 95 exposed at the opening of the resist pattern. Thereafter, the resist pattern for electroplating is removed by wet etching, and the exposed portion of the seed layer 95 for electroplating is then removed by wet etching.

  Next, as shown in FIGS. 40E and 41D, the sacrificial layer 94 is removed by wet etching. Through the above steps, the above-described switching element X3 is manufactured.

  In such a conventional method, the air gap in the open state between the contact electrode 92 and the contact electrode 93 or the protrusion 93a is the process described above with reference to FIGS. 40 (c) and 41 (a). This is substantially determined by controlling the depth of the concave portion 94a formed by the etching process in Step 1, that is, by controlling half-etching.

  However, in the processes of FIGS. 40C and 41A, half-etching cannot be accurately controlled, and it is difficult to form the recess 94a with high accuracy in terms of depth. Therefore, the conventional method involves difficulty in controlling the size of the air gap to be formed between the contact electrodes 92 and 93 with high accuracy. If the controllability of the air gap formation is low, the air gap in the open state between the contact electrodes 92 and 93 is relatively large (that is, varies) for each switching element to be manufactured. When this variation is large, the driving voltage for achieving the closed state in the switching element X3 tends to increase. This is because it is necessary to set the drive voltage sufficiently high so that the switching element X3 can operate even when the air gap between the contact electrodes 92 and 93 is relatively large. For this reason, the low controllability of the air gap formation is not preferable from the viewpoint of reducing the driving voltage of the element.

  In addition, the bottom surface of the recess 94a formed in the sacrificial layer 94 by the etching process in the steps of FIGS. 40C and 41A is relatively rough. Unevenness with a height difference of about 0.2 μm is generated on the bottom surface. In the conventional method, the surface roughness of the bottom surface of the concave portion 94a is substantially equal to the tip surface of the protrusion 93a of the contact electrode 93 to be formed, as shown in FIGS. 41 (c) and 41 (d). Is transferred to. That is, according to the conventional method, the tip surface of the protrusion 93a of the contact electrode 93 to be formed is also relatively rough and has unevenness with a height difference of about 0.2 μm. The tip surface of the protrusion 93a is a portion that contacts the contact electrode 92. The rougher the tip surface of the protrusion 93a, the smaller the contact area, and the contact resistance between the contact electrodes 92 and 93 (that is, the contact electrode). The resistance of the contact interface at the time of contact of 92 and 93 tends to increase. A large contact resistance between the contact electrode pairs is not preferable for reducing the insertion loss of the element.

  The present invention has been conceived under the circumstances as described above, and a switching element manufacturing method, a switching element, which is easy to control the formation of an air gap between contact electrode pairs and is suitable for reducing contact resistance, And it aims at providing a communication apparatus provided with a switching element.

  According to a first aspect of the present invention, a first contact electrode, and a second contact electrode having a portion that includes a protrusion extending toward the first contact electrode and faces the first contact electrode, There is provided a method for manufacturing a switching element in which first and second contact electrodes are provided so as to be able to approach and move apart and to come into contact with each other. This manufacturing method includes first to seventh steps. In the first step, a first contact electrode is formed on the substrate. In the second step, a sacrificial layer covering the first contact electrode is formed. In the third step, the sacrificial layer is patterned to form at least an opening that partially exposes the first contact electrode. This opening is for forming a protrusion of the second contact electrode. In the fourth step, a seed layer composed of at least two layers is formed over the portion exposed in the third step (patterning step) and the sacrificial layer. In the fifth step, a second contact electrode is formed having a portion that includes a protrusion that faces the first contact electrode and fills the opening through the sacrificial layer. In the sixth step, the sacrificial layer is removed. In the seventh step, at least the first contact electrode side layer (removal target layer) of the seed layer on the first contact electrode side surface in the protrusion is removed.

  The air gap between the first contact electrode and the second contact electrode (or its protrusion) in the switching element manufactured by this method is formed by removing the removal target layer in the seventh step. The removal target layer is a region in contact with the first contact electrode in the lowermost layer of the seed layer having a multilayer structure, and is formed in the fourth step. Therefore, the control accuracy or controllability of the air gap formation between the first and second contact electrodes in this method has the control accuracy or controllability of the thickness in the formation of the removal target layer (included in the fourth step). It is reflected directly. Since the film thickness control can be performed with higher accuracy than the half etching control described above with respect to the conventional method, the air gap in the present method directly reflects such film thickness control. The formation control can be performed with higher accuracy than the half etching control (that is, the conventional control method in forming the air gap) described above with respect to the conventional method. Thus, the present method can easily control the air gap formation between the first and second contact electrodes. High controllability of air gap formation is preferable from the viewpoint of reducing the drive voltage of the element.

  Further, in this method, the surface of the removal target layer formed on the first contact electrode in the above-described fourth step has high smoothness and is a recess formed by the half etching described above with respect to the conventional method. The surface irregularities are considerably smaller than the bottom surface of 94a. Then, the smoothness of the surface of the layer to be removed is reflected on the tip surface of the protrusion of the second contact electrode formed by this method. In the conventional method described above, relatively large irregularities on the bottom surface of the recess 94a are transferred to the tip surface of the protrusion 93a of the contact electrode 93, whereas in this method, the smoothness of the surface of the layer to be removed is reflected. As a result, the tip surface of the protrusion of the second contact electrode is also formed with high smoothness. The tip surface of the protrusion portion of the second contact electrode is a portion that contacts the first contact electrode. The higher the smoothness of the tip surface of the protrusion portion, the larger the contact area, and the first and second contact electrodes. The contact resistance between them tends to be small. Therefore, this method is suitable for reducing the contact resistance between the first and second contact electrodes. A low contact resistance between the first and second contact electrodes is preferable for reducing the insertion loss of the element.

  As described above, the switching element manufacturing method according to the first aspect of the present invention makes it easy to control the formation of the air gap between the first and second contact electrodes, and the contact resistance between the first and second contact electrodes. It is suitable for reducing this.

  The switching element manufacturing method according to the first aspect of the present invention preferably includes a step of forming a protective film on the first contact electrode, and in the third step (step of forming an opening), the sacrifice layer is patterned. In this way, at least a part of the protective film on the first contact electrode is exposed, and after the sixth step (step of removing the sacrificial layer), a step of removing the protective film from the first contact electrode is further included. The protective film removing step and the seventh step may be performed separately or in a single process.

  The air gap between the first contact electrode and the second contact electrode (or its protrusion) in the switching element manufactured by this method is removed in the seventh step by removing the protective film on the first contact electrode. Formed by removing the layer. The protective film is formed on the first contact electrode, and the removal target layer is a region in contact with the protective film in the lowermost layer of the multi-layered seed layer, and is formed in the fourth step. It is a film. Therefore, the control accuracy or controllability of the air gap formation between the first and second contact electrodes in this method directly reflects the control accuracy or controllability of the thickness in each film formation of the protective film and the layer to be removed. The Since the film thickness control can be performed with higher accuracy than the half etching control described above with respect to the conventional method, the air gap in the present method directly reflects such film thickness control. The formation control can be performed with higher accuracy than the half etching control (that is, the conventional control method in forming the air gap) described above with respect to the conventional method. Thus, the present method can easily control the air gap formation between the first and second contact electrodes.

  In the present method, the surface of the protective film formed on the first contact electrode has high smoothness. Therefore, the surface of the layer to be removed formed on the protective film is also highly smooth, and the surface unevenness is considerably smaller than the bottom surface of the recess 94a formed by the half etching described above with respect to the conventional method. Then, the smoothness of the surface of the layer to be removed is reflected on the tip surface of the protrusion of the second contact electrode formed by this method. Therefore, this method is suitable for reducing the contact resistance between the first and second contact electrodes.

  In addition, according to the present method using the protective film on the first contact electrode, it is possible to prevent a predetermined residue such as a resist from adhering to the first contact electrode. This contributes to reducing the contact resistance between the first and second contact electrodes.

  According to the second aspect of the present invention, the fixed portion, the movable portion extending with the fixed end fixed to the fixed portion, the first contact electrode provided on the movable portion, and the first contact electrode. There is provided a method for manufacturing a switching element including a second contact electrode including a projecting portion that extends and a portion facing the first contact electrode. This switching element manufacturing method includes first to ninth steps. In the first step, a first contact electrode is formed on a first layer of a material substrate having a laminated structure including a first layer, a second layer, and an intermediate layer between the first and second layers. In the second step, the movable part is formed in the first layer. In the third step, a sacrificial layer that covers the movable portion and the first contact electrode is formed. In the fourth step, the sacrificial layer is patterned to form at least an opening that partially exposes the first contact electrode. In the fifth step, a seed layer composed of at least two layers is formed over the portion exposed in the fourth step and the sacrificial layer. In the sixth step, a second contact electrode is formed having a portion that includes a protrusion that faces the first contact electrode through the sacrificial layer and fills the opening. In the seventh step, the sacrificial layer is removed. In the eighth step, the intermediate layer interposed between the second layer and the movable portion is removed. The seventh and eighth steps may be performed separately or in a single process. In the ninth step, at least the first contact electrode side layer (removal target layer) of the seed layer on the first contact electrode side surface in the protrusion is removed.

  The air gap between the first contact electrode and the second contact electrode (or its protrusion) in the switching element manufactured by this method is formed by removing the removal target layer in the ninth step. The removal target layer is a region in contact with the first contact electrode in the lowermost layer of the multi-layered seed layer, and is formed in the fifth step. Therefore, the control accuracy or controllability of the air gap formation between the first and second contact electrodes in the present method is the control accuracy or controllability of the thickness in the formation of the removal target layer (included in the fifth step). It is reflected directly. Since the film thickness control can be performed with higher accuracy than the half etching control described above with respect to the conventional method, the air gap in the present method directly reflects such film thickness control. The formation control can be performed with higher accuracy than the half etching control (that is, the conventional control method in forming the air gap) described above with respect to the conventional method. Thus, the present method can easily control the air gap formation between the first and second contact electrodes.

  Further, in this method, the surface of the removal target layer formed on the first contact electrode in the fifth step described above has high smoothness, and the recess 94a formed by the half etching described above with respect to the conventional method. The surface unevenness is considerably smaller than the bottom surface of. Then, the smoothness of the surface of the layer to be removed is reflected on the tip surface of the protrusion of the second contact electrode formed by this method. Therefore, this method is suitable for reducing the contact resistance between the first and second contact electrodes.

  As described above, in the switching element manufacturing method according to the second aspect of the present invention, it is easy to control the formation of the air gap between the first and second contact electrodes, and the contact resistance between the first and second contact electrodes. It is suitable for reducing this.

  The switching element manufacturing method according to the second aspect of the present invention preferably includes a step of forming a protective film on the first contact electrode, and in the fourth step, at least the first contact electrode is formed by patterning the sacrificial layer. The method further includes a step of exposing a part of the upper protective film and removing the protective film from the first contact electrode after the seventh step. The protective film removing step and the ninth step may be performed separately or in a single process.

  The air gap between the first contact electrode and the second contact electrode (or its protrusion) in the switching element manufactured by this method is removed in the ninth step by removing the protective film on the first contact electrode. Formed by removing the layer. The protective film is formed on the first contact electrode, and the removal target layer is a region in contact with the protective film in the lowermost layer of the multi-layered seed layer, and is formed in the fifth step. It is a film. Therefore, the control accuracy or controllability of the air gap formation between the first and second contact electrodes in this method directly reflects the control accuracy or controllability of the thickness in each film formation of the protective film and the layer to be removed. The Since the film thickness control can be performed with higher accuracy than the half etching control described above with respect to the conventional method, the air gap in the present method directly reflects such film thickness control. The formation control can be performed with higher accuracy than the half etching control (that is, the conventional control method in forming the air gap) described above with respect to the conventional method. Thus, the present method can easily control the air gap formation between the first and second contact electrodes.

  In the present method, the surface of the protective film formed on the first contact electrode has high smoothness. Therefore, the surface of the layer to be removed formed on the protective film is also highly smooth, and the surface unevenness is considerably smaller than the bottom surface of the recess 94a formed by the half etching described above with respect to the conventional method. Then, the smoothness of the surface of the layer to be removed is reflected on the tip surface of the protrusion of the second contact electrode formed by this method. Therefore, this method is suitable for reducing the contact resistance between the first and second contact electrodes.

  In addition, according to the present method using the protective film on the first contact electrode, it is possible to prevent a predetermined residue such as a resist from adhering to the first contact electrode. This contributes to reducing the contact resistance between the first and second contact electrodes.

  According to the third aspect of the present invention, the fixed portion, the movable portion extending with the fixed end fixed to the fixed portion, the first contact electrode provided on the movable portion, and the first contact electrode. A first contact electrode including a second contact electrode including a first protrusion extending and facing the first contact electrode; and a second protrusion extending toward the first contact electrode. There is provided a method for manufacturing a switching element comprising a third contact electrode having opposing portions. This method includes first to ninth steps, protective film formation, protective film partial removal process, and protective film removal process. In the first step, a first contact electrode is formed on a first layer of a material substrate having a laminated structure including a first layer, a second layer, and an intermediate layer between the first and second layers. In the protective film forming step, a protective film is formed on the first contact electrode. In the second step, the movable part is formed in the first layer. In the third step, a sacrificial layer that covers the movable portion and the first contact electrode is formed. In the fourth step, the sacrificial layer is patterned to form at least a first opening and a second opening that partially expose the protective film on the first contact electrode. In the protective film partial removal step, the region exposed to the first opening in the protective film is removed. In the fifth step, a seed layer composed of at least two layers is formed over the portion exposed in the fourth step and the protective film partial removal step and the sacrificial layer. In the sixth step, a second contact electrode having a portion including a first protrusion that faces the first contact electrode through the sacrificial layer and fills the first opening is formed, and the second contact electrode is formed through the sacrificial layer. A third contact electrode is formed having a portion that includes a second protrusion that faces the one contact electrode and fills the second opening. In the seventh step, the sacrificial layer is removed. In the eighth step, the intermediate layer interposed between the second layer and the movable portion is removed. The seventh and eighth steps may be performed separately or in a single process. In the ninth step, at least the first contact electrode side layer (removal target layer) of the seed layer on the first contact electrode side surface in the first and second protrusions is removed. In the protective film removing step, the protective film is removed from the first contact electrode. The ninth step and the protective film removing step may be performed separately or in a single process.

  The air gap between the first contact electrode and the second contact electrode (or the first protrusion) in the switching element manufactured by this method removes the removal target layer on the first protrusion in the ninth step. Formed by. The removal target layer is a region in contact with the first contact electrode in the lowermost layer of the seed layer having a multilayer structure, and is formed in the fifth step. For this reason, the control accuracy or controllability of the air gap formation between the first and second contact electrodes in this method includes the control accuracy or controllability of the thickness in the formation of the removal target layer (included in the fifth step). Is directly reflected. Since the film thickness control can be performed with higher accuracy than the half etching control described above with respect to the conventional method, the first film thickness control in the present method directly reflects such film thickness control. And the control of the air gap formation between the second contact electrodes can be performed with higher accuracy than the half etching control (that is, the conventional control method in the air gap formation) described above with respect to the conventional method. Thus, the present method can easily control the air gap formation between the first and second contact electrodes.

  Further, in this method, the surface of the removal target layer formed on the first contact electrode in the fifth step described above has high smoothness, and the recess 94a formed by the half etching described above with respect to the conventional method. The surface unevenness is considerably smaller than the bottom surface of. The smoothness of the removal target layer surface is reflected on the tip surface of the first protrusion of the second contact electrode formed by this method. The tip surface of the first protrusion of the second contact electrode is a portion that contacts the first contact electrode. The higher the smoothness of the tip surface of the first protrusion, the larger the contact area becomes. The contact resistance between the second contact electrodes tends to be small. Therefore, this method is suitable for reducing the contact resistance between the first and second contact electrode pairs.

  On the other hand, the air gap between the first contact electrode and the third contact electrode (or the second protrusion) in the switching element manufactured by this method removes the protective film on the first contact electrode and the ninth step described above. It is formed by removing the removal target layer on the second protrusion side. The protective film is formed on the first contact electrode, and the removal target layer is a region in contact with the protective film in the lowermost layer of the multi-layered seed layer, and is in the fifth step. The film is formed. Therefore, the control accuracy or controllability of the air gap formation between the first and third contact electrodes in this method directly reflects the control accuracy or controllability of the thickness in each film formation of the protective film and the removal target layer. Is done. Since the film thickness control can be performed with higher accuracy than the half etching control described above with respect to the conventional method, the first film thickness control in the present method directly reflects such film thickness control. And the control of the air gap formation between the third contact electrodes can be performed with higher accuracy than the half etching control (that is, the conventional control method in the air gap formation) described above with respect to the conventional method. Thus, the present method can easily control the air gap formation between the first and third contact electrodes.

  In the present method, the surface of the protective film formed on the first contact electrode has high smoothness. Therefore, the surface of the layer to be removed formed on the protective film is also highly smooth, and the surface unevenness is considerably smaller than the bottom surface of the recess 94a formed by the half etching described above with respect to the conventional method. The smoothness of the surface of the layer to be removed is reflected on the tip surface of the second protrusion of the third contact electrode formed by this method. The tip surface of the second protrusion of the third contact electrode is a portion that contacts the first contact electrode. The higher the smoothness of the tip surface of the second protrusion, the larger the contact area becomes. The contact resistance between the third contact electrodes tends to be small. Therefore, this method is suitable for reducing the contact resistance between the first and third contact electrodes.

  As described above, in the switching element manufacturing method according to the third aspect of the present invention, it is easy to control the air gap formation between the first and second contact electrode pairs and the contact resistance between the first and second contact electrode pairs. In addition, the air gap formation between the first and third contact electrode pairs can be easily controlled and the contact resistance between the first and third contact electrode pairs can be reduced.

  In addition, according to the present method using the protective film on the first contact electrode, it is possible to prevent a predetermined residue such as a resist from adhering to the first contact electrode. This contributes to reducing the contact resistance between the first and second contact electrodes and the contact resistance between the first and third contact electrodes.

  In the method according to the third aspect of the present invention, preferably, the second step is performed before the first step, and the eighth step is performed after the second step and before the first step. By performing the eighth step before the first step, it is avoided that the first contact electrode (formed in the first step) is exposed to the removal process by the etching method in the eighth step, for example. be able to.

  In the first to third aspects of the present invention, preferably, the lowermost layer and / or the protective film in the seed layer is made of chromium, molybdenum, titanium, nickel, or an alloy containing these.

  Preferably, the sacrificial layer on the first to third sides is made of polyimide. Polyimide can be removed by applying oxygen plasma. Therefore, when a sacrificial layer made of polyimide is employed, it is possible to avoid using a wet etching method as a removing method in the sacrificial layer removing step. Accordingly, the first to third contact electrodes are etched into the etching solution in the step. Can be avoided.

  According to a fourth aspect of the present invention, a switching element is provided. This switching element is manufactured by the method described in any one of the methods according to the first to third aspects described above.

  According to the 5th side surface of this invention, a communication apparatus provided with the switching element which concerns on a 4th side surface is provided. This communication device includes, for example, a plurality of RF circuits and a plurality of antennas corresponding to the switching elements in addition to the switching element.

  1 to 5 show a switching element X1 according to the first embodiment of the present invention. FIG. 1 is a plan view of the switching element X1, and FIG. 2 is a partially omitted plan view of the switching element X1. 3 to 5 are sectional views taken along lines III-III, IV-IV, and VV in FIG. 1, respectively.

  The switching element X1 includes a base substrate S1, a fixed portion 11, a movable portion 12, a contact electrode 13, a pair of contact electrodes 14 (represented by virtual lines in FIG. 2), a drive electrode 15, and a drive electrode 16 ( 2).

  As shown in FIGS. 3 to 5, the fixing part 11 is bonded to the base substrate S <b> 1 via the boundary layer 17. The fixing portion 11 is made of a silicon material such as single crystal silicon. The silicon material constituting the fixing portion 11 preferably has a resistivity of 1000 Ω · cm or more. The boundary layer 17 is made of, for example, silicon dioxide.

For example, as shown in FIG. 1, FIG. 2, or FIG. 5, the movable portion 12 has a fixed end 12 a fixed to the fixed portion 11 and a free end 12 b and extends along the base substrate S <b> 1. 18 is surrounded by the fixing portion 11. The thickness T shown in FIGS. 3 and 4 for the movable portion 12 is, for example, 15 μm or less. Further, the movable portion 12, the length L ₁ shown in FIG. 2 is a 650~1000μm example, the length L ₂ is 200~400μm example. The width of the slit 18 is, for example, 1.5 to 2.5 μm. The movable part 12 is made of, for example, single crystal silicon.

  The contact electrode 13 is provided on the movable portion 12 near the free end 12b, as clearly shown in FIG. The thickness of the contact electrode 13 is, for example, 0.5 to 2 μm. The contact electrode 13 is made of a predetermined conductive material and has, for example, a laminated structure including a Mo base film and an Au film thereon.

  As shown in FIG. 3 or FIG. 5, the contact electrode 14 is erected on the fixed portion 11 and has a protrusion 14 a that extends toward the contact electrode 13. The protruding portion 14a is a portion for contacting the contact electrode 13 (in FIG. 2, a portion where the protruding portion 14a can contact with the contact electrode 13 is indicated by a black solid). The protrusion length of the protrusion 14a is 0.8 to 4 μm. Each contact electrode 14 is connected to a predetermined circuit to be switched through a predetermined wiring (not shown). As a constituent material of the contact electrode 14, Au can be adopted.

  The drive electrode 15 is provided over the movable part 12 and the fixed part 11 as shown in FIG. The thickness of the drive electrode 15 is, for example, 0.5 to 2 μm. As the constituent material of the drive electrode 15, the same constituent material as that of the contact electrode 13 can be employed.

  The drive electrode 16 is for generating an electrostatic attractive force (drive force) between the drive electrode 15 and, as shown well in FIG. It is erected so as to straddle the top of 15. The thickness of the drive electrode 16 is, for example, 10 μm or more. The drive electrode 16 is grounded via a predetermined wiring (not shown). As the constituent material of the drive electrode 16, the same constituent material as that of the contact electrode 14 can be employed.

  In the switching element X1 having the above-described structure, when a potential is applied to the drive electrode 15, an electrostatic attractive force is generated between the drive electrodes 15 and 16. When the applied potential is sufficiently high, the movable portion 12 operates or elastically deforms until the contact electrode 13 comes into contact with the protrusion 14 a of the contact electrode 14. In this way, the closed state of the switching element X1 is achieved. In the closed state, the contact electrode 13 electrically bridges the pair of contact electrodes 14, and current is allowed to pass between the pair of contact electrodes 14. By such a switch-on operation, for example, an on state of a high frequency signal can be achieved.

  On the other hand, in the switching element X1 in the closed state, when the electrostatic attraction acting between the drive electrodes 15 and 16 is extinguished by stopping the potential application to the drive electrode 15, the movable portion 12 returns to its natural state. The contact electrode 13 is separated from the protrusion 14 a of the contact electrode 14. In this way, the open state of the switching element X1 as shown in FIGS. 3 and 5 is achieved. In the open state, the pair of contact electrodes 14 are electrically separated, and current is prevented from passing between the pair of contact electrodes 14. Such a switch-off operation can achieve, for example, an off state of a high-frequency signal. Further, the switching element X1 in such an open state can be switched again to the closed state or the on state by the above-described switch-on operation.

  6 to 9 show the first manufacturing method of the switching element X1 as a change in cross section corresponding to FIGS. 3 and 4. 10 to 12 show an enlarged view of the process in the vicinity of the protrusion forming portion in the manufacturing method.

  In this method, first, a material substrate S1 'as shown in FIG. The material substrate S <b> 1 ′ is an SOI (silicon on insulator) substrate and has a stacked structure including a first layer 101, a second layer 102, and an intermediate layer 103 therebetween. In the present embodiment, for example, the thickness of the first layer 101 is 15 μm, the thickness of the second layer 102 is 525 μm, and the thickness of the intermediate layer 103 is 4 μm. The first layer 101 is made of, for example, single crystal silicon, and is processed into the above-described fixed portion 11 and movable portion 12. The second layer 102 is made of single crystal silicon, for example, and is processed into the above-described base substrate S1. The intermediate layer 103 is made of, for example, silicon dioxide, and is processed into the boundary layer 17 described above.

  Next, as shown in FIG. 6B, a conductor film 104 is formed on the first layer 101. For example, Mo is deposited on the first layer 101 by sputtering, and then Au is deposited thereon. The thickness of the Mo film is, for example, 50 nm, and the thickness of the Au film is, for example, 500 nm.

  Next, as shown in FIG. 6C, resist patterns 105 and 106 are formed on the conductor film 104 by photolithography. The resist pattern 105 has a pattern shape corresponding to the contact electrode 13. The resist pattern 106 has a pattern shape corresponding to the drive electrode 15.

  Next, as shown in FIG. 7A, the contact film 13 and the drive electrode are formed on the first layer 101 by etching the conductive film 104 using the resist patterns 105 and 106 as a mask. 15 is formed. As an etching method in this step, ion milling (for example, physical etching with Ar ions) can be employed. Ion milling can also be employed as an etching method for the metal materials described later.

Next, after the resist patterns 105 and 106 are removed, as shown in FIG. 7B, the first layer 101 is etched to form the slits 18. Specifically, after a predetermined resist pattern is formed on the first layer 101 by a photolithography method, the first layer 101 is subjected to anisotropic etching using the resist pattern as a mask. As anisotropic etching, DRIE (deep reactive ion etching) can be employed. In DRIE, good anisotropic etching can be performed in a Bosch process in which etching performed using SF ₆ gas and sidewall protection performed using C ₄ F ₈ gas are alternately repeated. Such DRIE Bosch process can also be adopted for DRIE described later. In this step, the fixed portion 11 and the movable portion 12 are formed.

  Next, as shown in FIG. 7C, the sacrificial layer 107 is formed on the first layer 101 side of the material substrate S1 ′ so as to cover the slit 18 while covering the movable portion 12, the contact electrode 13, and the drive electrode 15. Form. For example, silicon dioxide can be used as the sacrificial layer material. As a method for forming the sacrificial layer 107, for example, a plasma CVD method or a sputtering method can be employed. The thickness of the sacrificial layer 107 to be formed is 5 μm, for example. Moreover, you may employ | adopt a polyimide as a sacrificial layer material.

  Next, by patterning the sacrificial layer 107, an opening 107a is formed as shown in FIGS. 8A and 10A to partially expose the contact electrode 13, and FIG. Openings 107b and 107c are formed as shown in FIG. Specifically, after a predetermined resist pattern is formed on the sacrificial layer 107 by a photolithography method, the sacrificial layer 107 is etched using the resist pattern as a mask. As an etching method, wet etching can be employed. As an etchant for wet etching, for example, buffered hydrofluoric acid (BHF) can be employed. BHF can also be employed in the later wet etching for the sacrificial layer 107. The openings 107a are for forming the protrusions 14a of the contact electrodes 14, respectively. Each of the openings 107b is for exposing a region where the contact electrode 14 is bonded in the fixed portion 11. The opening 107c is for exposing a region where the drive electrode 16 is joined in the fixed portion 11.

  Next, for example, as shown in FIG. 10B, a first seed layer 108a is formed on the portion exposed in the previous step (patterning step of the sacrificial layer 107) and on the sacrificial layer 107 (for simplification of the drawing). Therefore, it is omitted in FIGS. 8 and 9). The first seed layer 108a is made of a material having good adhesion to the first layer 101 of the material substrate S1 ', and is made of, for example, Cr, Mo, Ti, Ni, or an alloy containing these. Such a first seed layer 108a is formed to a thickness of 1 μm, for example, by sputtering.

  Next, a second seed layer 108b is formed on the first seed layer 108a formed as described above, for example, as shown in FIG. 10C (in FIG. 8 and FIG. (Omitted). The second seed layer 108b is made of a material having good adhesion to the later-described plating forming portion. Such a second seed layer 108b can be formed, for example, by depositing 300 nm thick Au by sputtering. The second seed layer 108b and the first seed layer 108a described above form a current-carrying seed layer 108 that is used when the later-described electroplating method is performed.

  Next, as shown in FIGS. 8B and 11A, a resist pattern 109 is formed. The resist pattern 109 has an opening 109 a corresponding to each contact electrode 14 and an opening 109 b corresponding to the drive electrode 16.

  Next, as shown in FIGS. 8C and 11B, the contact electrodes 14 and the drive electrodes 16 each having a protrusion 14a filling the opening 107a are formed. Specifically, for example, Au is grown by electroplating on the seed layer 108 exposed without being covered with the resist pattern 109. The thickness of the plating material to be grown is, for example, 20 μm.

  Next, as shown in FIG. 9A, the resist pattern 109 is removed by wet etching, for example.

  Next, the exposed portion of the second seed layer 108b is removed, for example, as shown in FIG. When the second seed layer 108b is made of, for example, gold, it is preferable to employ ion milling as a removal method in this step.

  Next, the exposed portion of the first seed layer 108a is removed, for example, as shown in FIG. When the first seed layer 108a is made of Mo, for example, it is preferable to employ reactive ion etching as a removal method in this step.

  Next, as shown in FIGS. 9B and 12B, a part of the sacrificial layer 107 and the intermediate layer 103 is removed. Specifically, wet etching is performed on the sacrificial layer 107 and the intermediate layer 103. In this etching process, the sacrificial layer 107 is first removed, and then a part of the intermediate layer 103 is removed from the portion facing the slit 18. This etching process stops after an appropriate gap is formed between the entire movable portion 12 and the second layer 102. In this way, the boundary layer 17 remains in the intermediate layer 103. The second layer 102 constitutes the base substrate S1.

  Next, as shown in FIG. 12C, at least the first seed layer 108a (removal of the seed layer 108 on the contact electrode 13 side surface in the protrusion 14a of the contact electrode 14 is removed by wet etching. The target layer R1) is removed. As a result, as shown in FIGS. 9C and 12C, an air gap G1 is formed between the contact electrode 13 and the protrusion 14a of the contact electrode 14. As the etching solution in this step, when the first seed layer 108a is made of Cr, for example, an aqueous solution of ceric ammonium nitrate can be used, and when the first seed layer 108a is made of Mo, for example, An aqueous solution containing nitric acid and phosphoric acid can be used. When the first seed layer 108a is made of Ti, for example, BHF can be used. When the first seed layer 108a is made of Ni, for example, An aqueous solution containing phosphoric acid, nitric acid and acetic acid can be used. Further, in this step, the removal target layer R1 which is a part of the first seed layer 108a is appropriately removed, and then the contact electrode 14 and the drive electrode 16 standing on the first layer 101 of the material substrate S1 ′. The etching time is adjusted so that the first seed layer 108a forming the base end of the first seed layer 108a is not excessively eroded. Since the junction area of the contact electrode 14 and the drive electrode 16 with respect to the first layer 101 is considerably large compared to the size of the protrusion 14a, such adjustment is possible.

  After this step, the movable portion 12 is slightly warped, and the movable portion 12 is slightly displaced toward the contact electrode 14 (not shown). The drive electrode 15 formed as described above is subjected to an internal stress during the formation process, and the drive electrode 15 and the movable portion 12 to which the drive electrode 15 is joined are warped by the action of the internal stress. Specifically, the movable portion 12 is deformed or warped so that the free end 12 b of the movable portion 12 slightly approaches the contact electrode 14. The amount of displacement of the free end 12b and the contact electrode 13 due to the warpage is controlled with high accuracy by controlling the thickness of the drive electrode 15 formed and formed on the movable portion 12 as described above. Can do.

  Thereafter, the entire device is dried by a supercritical drying method as necessary. According to the supercritical drying method, it is possible to appropriately avoid the sticking phenomenon in which the movable portion 12 sticks to the base substrate S1 and the like. As described above, the switching element X1 can be manufactured.

  The air gap G1 between the contact electrode 13 and the contact electrode 14 (or the protrusion 14a thereof) in the switching element X1 manufactured by this method removes the removal target layer R1 in the process described above with reference to FIG. It is formed by doing. The removal target layer R1 is a region in contact with the contact electrode 13 in the lowermost first seed layer 108a of the multi-layered seed layer 108, and is formed by the process described above with reference to FIG. It is. Therefore, the control accuracy or controllability of the formation of the removal target layer R1 directly reflects the control accuracy or controllability of the air gap formation between the contact electrodes 13 and 14 in this method. Since the film thickness control can be performed with higher accuracy than the half etching control described above with respect to the conventional method, the air gap in the present method directly reflects such film thickness control. The formation control can be performed with higher accuracy than the half etching control (that is, the conventional control method in forming the air gap) described above with respect to the conventional method. Thus, this method can easily control the air gap formation between the contact electrodes 13 and 14. High controllability of air gap formation is preferable from the viewpoint of lowering the driving voltage of the switching element X1.

  Further, in this method, the surface of the removal target layer R1 formed on the contact electrode 13 in the step described above with reference to FIG. 10B has high smoothness, and the half described above with respect to the conventional method. The surface unevenness is considerably smaller than the bottom surface of the recess 94a formed by etching. The smoothness of the surface of the removal target layer R1 is reflected on the tip surface of the protrusion 14a of the contact electrode 14 formed by this method. In the conventional method described above, relatively large irregularities on the bottom surface of the recess 94a are transferred to the tip surface of the protrusion 93a of the contact electrode 93, whereas in this method, the smoothness of the surface of the removal target layer R1 is reduced. By being reflected, the tip surface of the protrusion 14a of the contact electrode 14 is also formed with high smoothness. The tip surface of the protrusion 14a of the contact electrode 14 is a portion that contacts the contact electrode 13. However, the higher the smoothness of the tip surface of the protrusion 14a, the larger the contact area becomes. Contact resistance tends to be small. Therefore, this method is suitable for reducing the contact resistance between the contact electrodes 13 and 14. A low contact resistance between the contact electrodes 13 and 14 is preferable for reducing the insertion loss of the switching element X1.

  As described above, the first manufacturing method of the switching element X1 is easy to control the formation of the air gap between the contact electrodes 13 and 14, and is suitable for reducing the contact resistance between the contact electrodes 13 and 14.

  In addition, in this method, the contact electrode 14 having a portion facing the contact electrode 13 can be formed thick by a plating method. Therefore, the pair of contact electrodes 14 can be set to have a sufficient thickness for realizing a desired low resistance. The thick contact electrode 14 is preferable for reducing the insertion loss of the switching element X1.

  13 to 16 show a second method for manufacturing the switching element X1 as a change in cross section corresponding to FIGS. 3 and 4. FIG. 17 to FIG. 19 show an enlarged process in the vicinity of the protrusion forming portion in the manufacturing method.

  In this method, first, as shown in FIG. 13A, the conductor film 104 and the protective film 110 are formed on the first layer 101 of the material substrate S1 'described above. The formation of the conductor film 104 is specifically the same as that described above with reference to FIG. 6B regarding the first manufacturing method. The protective film 110 is formed by sputtering, for example, and is made of, for example, Cr, Mo, Ti, Ni, or an alloy containing these. The thickness of the protective film 110 is, for example, 500 nm.

  Next, as shown in FIG. 13B, resist patterns 105 and 106 are formed on the protective film 110 by photolithography. The resist pattern 105 has a pattern shape corresponding to the contact electrode 13. The resist pattern 106 has a pattern shape corresponding to the drive electrode 15.

  Next, as shown in FIG. 13C, the protective films 110a and 110b are formed by etching the protective film 110 using the resist patterns 105 and 106 as a mask. As an etching technique in this step, reactive ion etching can be employed.

  Next, as shown in FIG. 14A, the contact film 13 and the drive electrode 15 are formed by etching the conductive film 104 using the resist patterns 105 and 106 as a mask. As an etching method in this step, ion milling can be employed.

  Next, after the resist patterns 105 and 106 are removed, as shown in FIG. 14B, the first layer 101 is etched to form the slits 18. Specifically, the first manufacturing method is the same as that described above with reference to FIG. In this step, the fixed portion 11 and the movable portion 12 are formed.

  Next, as illustrated in FIG. 14C, a sacrificial layer 107 is formed on the first layer 101 side of the material substrate S <b> 1 ′ so as to close the slit 18. Specifically, the first manufacturing method is the same as that described above with reference to FIG.

  Next, by patterning the sacrificial layer 107, an opening 107a is formed as shown in FIGS. 15A and 17A to partially expose the protective film 110a, and FIG. Openings 107b and 107c are formed as shown in FIG. Specifically, the first manufacturing method is the same as described above with reference to FIGS. 8A and 10A.

  Next, for example, as shown in FIG. 17B, a first seed layer 108a is formed over the portion exposed in the previous step (patterning step of the sacrificial layer 107) and the sacrificial layer 107 (for simplification of the drawing). Therefore, it is omitted in FIGS. 15 and 16). The first seed layer 108a is made of a material having good adhesion to the first layer 101 of the material substrate S1 ', and is made of, for example, Cr, Mo, Ti, Ni, or an alloy containing these. Such a first seed layer 108a is formed to a thickness of 1 μm, for example, by sputtering.

  Next, the second seed layer 108b is formed on the first seed layer 108a formed as described above, for example, as shown in FIG. 17C (in FIG. 15 and FIG. (Omitted). The second seed layer 108b is made of a material having good adhesion to the later-described plating forming portion. Such a second seed layer 108b can be formed, for example, by depositing 300 nm thick Au by sputtering. The second seed layer 108b and the first seed layer 108a described above form a current-carrying seed layer 108 that is used when the later-described electroplating method is performed.

  Next, as shown in FIGS. 15B and 18A, a resist pattern 109 is formed. The resist pattern 109 has an opening 109 a corresponding to each contact electrode 14 and an opening 109 b corresponding to the drive electrode 16.

  Next, as shown in FIG. 15C and FIG. 18B, the contact electrodes 14 and the drive electrodes 16 each having a protrusion 14a filling the opening 107a are formed. Specifically, the first manufacturing method is the same as described above with reference to FIGS. 8C and 11B.

  Next, as shown in FIG. 16A, the resist pattern 109 is removed by wet etching, for example.

  Next, the exposed portion of the second seed layer 108b is removed, for example, as shown in FIG. Subsequently, the exposed portion of the first seed layer 108a is removed, for example, as shown in FIG.

  Next, as shown in FIGS. 16B and 19B, a part of the sacrificial layer 107 and the intermediate layer 103 is removed. Specifically, the first manufacturing method is the same as described above with reference to FIGS. 9B and 12B.

  Next, as shown in FIG. 19C, the protective films 110a and 110b and the seed layer 108 on the contact electrode 13 side surface of the protrusion 14a of the contact electrode 14 are wet-etched by wet etching. The 1 seed layer 108a (removal target layer R2) is removed. As a result, as shown in FIGS. 16C and 19C, an air gap G <b> 2 is formed between the contact electrode 13 and the protrusion 14 a of the contact electrode 14. When the protective films 110a and 110b and the first seed layer 108a or the removal target layer R2 are made of different materials, the wet etching for the protective films 110a and 110b and the wet etching for the first seed layer 108a are performed by different processes, and the same material is used. In this case, the wet etching for the protective films 110a and 110b and the wet etching for the first seed layer 108a are performed by a single process. As the etching solution, when the protective films 110a and 110b and the first seed layer 108a are made of Cr, for example, an aqueous solution of ceric ammonium nitrate can be used, and the protective films 110a and 110b and the first seed layer 108a can be used. When made of Mo, for example, an aqueous solution containing nitric acid and phosphoric acid can be used. When the protective films 110a and 110b and the first seed layer 108a are made of Ti, for example, BHF can be used. When the protective films 110a and 110b and the first seed layer 108a are made of Ni, for example, an aqueous solution containing phosphoric acid, nitric acid, and acetic acid can be used. Further, in this step, the removal target layer R2 that is a part of the first seed layer 108a is appropriately removed, and then the contact electrode 14 and the drive electrode 16 standing on the first layer 101 of the material substrate S1 ′. The etching time is adjusted so that the first seed layer 108a forming the base end of the first seed layer 108a is not excessively eroded. Since the junction area of the contact electrode 14 and the drive electrode 16 with respect to the first layer 101 is considerably large compared to the size of the protrusion 14a, such adjustment is possible.

  After this step, the movable portion 12 is slightly warped, and the movable portion 12 is slightly displaced toward the contact electrode 14 (not shown). With respect to the amount of displacement of the free end 12b and the contact electrode 13 caused by the warp of the movable part 12, the thickness of the drive electrode 15 formed on the movable part 12 as described above is controlled with high accuracy. Can be controlled. Specifically, the first manufacturing method is as described above with reference to FIG.

  Thereafter, the entire device is dried by a supercritical drying method as necessary. As described above, the switching element X1 can be manufactured.

  The air gap G2 between the contact electrode 13 and the contact electrode 14 (or its protrusion 14a) in the switching element X1 manufactured by this method is protected as described above with reference to FIGS. 16 (c) and 19 (c). It is formed by removing the film 110a and the removal target layer R2. The protective film 110a is formed on the contact electrode 13, and the removal target layer R2 is a region in contact with the protective film 110a in the lowermost first seed layer 108a of the multi-layered seed layer 108. Then, the film is formed by the process described above with reference to FIG. Therefore, the control accuracy or controllability of the air gap formation between the contact electrodes 13 and 14 in this method directly reflects the control accuracy or controllability of the thickness in each film formation of the protective film 110a and the removal target layer R2. The Since the film thickness control can be performed with higher accuracy than the half etching control described above with respect to the conventional method, the air gap in the present method directly reflects such film thickness control. The formation control can be performed with higher accuracy than the half etching control (that is, the conventional control method in forming the air gap) described above with respect to the conventional method. Thus, this method can easily control the air gap formation between the contact electrodes 13 and 14. High controllability of air gap formation is preferable from the viewpoint of lowering the driving voltage of the switching element X1.

  In this method, the surface of the protective film 110a formed on the contact electrode 13 is highly smooth. Therefore, the surface of the removal target layer R2 formed on the protective film 110a is also highly smooth, and the surface unevenness is considerably smaller than the bottom surface of the recess 94a formed by the half etching described above with respect to the conventional method. The smoothness of the surface of the removal target layer R2 is reflected on the tip surface of the protrusion 14a of the contact electrode 14 formed by this method. Therefore, this method is suitable for reducing the contact resistance between the contact electrodes 13 and 14. A low contact resistance between the contact electrodes 13 and 14 is preferable for reducing the insertion loss of the switching element X1.

  As described above, the second manufacturing method of the switching element X1 is easy to control the formation of the air gap between the contact electrodes 13 and 14, and is suitable for reducing the contact resistance between the contact electrodes 13 and 14.

  In this method, the resist pattern 105 that functions as a mask when patterning the contact electrode 13 is not directly stacked on the contact electrode 13 as shown in FIG. And formed on the contact electrode 13. Therefore, in this method, the resist residue does not directly adhere to the contact electrode 13 after the step for removing the resist pattern 105 is performed. Even if a resist residue derived from the resist pattern 105 exists, it adheres to the protective film 110a. The resist residue is removed along with the protective film 110a when the protective film 110a is removed in the process described above with reference to FIGS. 16C and 19C. Further, even if a residue derived from the sacrificial layer 107 adheres to the protective film 110a, the residue is also removed along with the protective film 110a. Such a method is preferable for reducing the contact resistance between the contact electrodes 13 and 14. If a resist residue is attached to the contact electrode 13 of the manufactured switching element X1, the contact resistance between the contact electrodes 13 and 14 may increase.

  20 to 22 show a third manufacturing method of the switching element X1 as a change in cross section corresponding to FIGS. 3 and 4. 23 to 25 show an enlarged view of the process in the vicinity of the protrusion forming portion in the manufacturing method.

  In this method, first, as shown in FIG. 20A, the slit 18 is formed by performing an etching process on the first layer 101 of the material substrate S1 'described above. Specifically, the first manufacturing method is the same as described above with reference to FIG. In this step, the fixed portion 11 and the movable portion 12 are formed.

  Next, as shown in FIG. 20B, a part of the intermediate layer 103 is removed. Specifically, the intermediate layer 103 is subjected to a wet etching process using, for example, BHF as an etching solution. In this etching process, a part of the intermediate layer 103 is removed from the portion facing the slit 18. This etching process stops after an appropriate gap is formed between the entire movable portion 12 and the second layer 102. In this way, the boundary layer 17 remains in the intermediate layer 103. The second layer 102 constitutes the base substrate S1.

  Next, as shown in FIG. 20C, the contact electrode 13 and the protective film 110a thereon, and the drive electrode 15 and the protective film 110b thereon are formed. The method of forming the contact electrode 13 and the drive electrode 15 is the same as that described above in the first manufacturing method. The formation method of the protective films 110a and 110b is the same as that described above in the second manufacturing method.

  Next, as shown in FIG. 21A, the first layer of the material substrate S1 ′ is formed so as to close the slit 18 while covering the movable portion 12, the contact electrode 13, the drive electrode 15, and the protective films 110a and 110b. A sacrificial layer 111 is formed on the 101 side. For example, polyimide can be used as the sacrificial layer material. The sacrificial layer 111 is formed by, for example, a spin coating method. The thickness of the sacrificial layer 111 to be formed is, for example, 5 μm.

  Next, by patterning the sacrificial layer 111, an opening 111a is formed as shown in FIGS. 21B and 23A to partially expose the protective film 110a, and FIG. Openings 111b and 111c are formed as shown in FIG. Specifically, after a predetermined resist pattern is formed on the sacrificial layer 111 by a photolithography method, the sacrificial layer 111 is etched using the resist pattern as a mask. As an etching method, wet etching can be employed. As an etchant for wet etching, for example, BHF can be employed. Alternatively, when a material having photosensitivity is used as the sacrificial layer material, the sacrificial layer 111 can be patterned by exposure and development. The openings 111a are for forming the protrusions 14a of the contact electrodes 14, respectively. Each of the openings 111b is for exposing a region where the contact electrode 14 is bonded in the fixed portion 11. The opening 111c is for exposing a region where the drive electrode 16 is joined in the fixed portion 11.

  Next, a first seed layer 108a is formed on the portion exposed in the previous step (patterning step of the sacrificial layer 111) and on the sacrificial layer 111, for example, as shown in FIG. Therefore, it is omitted in FIGS. 21 and 22). The first seed layer 108a is made of a material having good adhesion to the first layer 101 of the material substrate S1 ', and is made of, for example, Cr, Mo, Ti, Ni, or an alloy containing these. Such a first seed layer 108a is formed to a thickness of 1 μm, for example, by sputtering.

  Next, the second seed layer 108b is formed on the first seed layer 108a formed as described above, for example, as shown in FIG. 23C (in FIG. 21 and FIG. (Omitted). The second seed layer 108b is made of a material having good adhesion to the later-described plating forming portion. Such a second seed layer 108b can be formed, for example, by depositing 300 nm thick Au by sputtering. The second seed layer 108b and the first seed layer 108a described above form a current-carrying seed layer 108 that is used when the later-described electroplating method is performed.

  Next, as shown in FIGS. 21C and 24A, a resist pattern 109 is formed. The resist pattern 109 has an opening 109 a corresponding to each contact electrode 14 and an opening 109 b corresponding to the drive electrode 16.

  Next, as shown in FIGS. 22A and 24B, the contact electrodes 14 and the drive electrodes 16 each having a protrusion 14a filling the opening 111a are formed. Specifically, for example, Au is grown by electroplating on the seed layer 108 exposed without being covered with the resist pattern 109. The thickness of the plating material to be grown is, for example, 20 μm.

  Next, after removing the resist pattern 109 by, for example, wet etching, the exposed portion of the second seed layer 108b is removed, for example, as shown in FIG. Subsequently, the exposed portion of the first seed layer 108a is removed, for example, as shown in FIG.

  Next, as shown in FIGS. 22B and 25B, the sacrificial layer 111 is removed. As a removal method, for example, a method of removing by applying oxygen plasma can be employed.

  Next, as shown in FIG. 25C, the protective films 110a and 110b and the seed layer 108 on the contact electrode 13 side surface of the protrusion 14a of the contact electrode 14 are wet-etched by wet etching. The 1 seed layer 108a (removal target layer R2) is removed. As a result, an air gap G2 is formed between the contact electrode 13 and the protrusion 14a of the contact electrode 14, as shown in FIGS. 22 (c) and 25 (c). Specifically, this step is the same as that described above with reference to FIGS. 16C and 19C with respect to the second manufacturing method.

  After this step, the movable portion 12 is slightly warped, and the movable portion 12 is slightly displaced toward the contact electrode 14 (not shown). With respect to the amount of displacement of the free end 12b and the contact electrode 13 caused by the warp of the movable part 12, the thickness of the drive electrode 15 formed on the movable part 12 as described above is controlled with high accuracy. Can be controlled. Specifically, the first manufacturing method is as described above with reference to FIG.

  Thereafter, the entire device is dried by a supercritical drying method as necessary. As described above, the switching element X1 can be manufactured.

  The third manufacturing method of the switching element X1 makes it easy to control the formation of the air gap between the contact electrodes 13 and 14 and reduces the contact resistance between the contact electrodes 13 and 14 for the same reason as the second manufacturing method. Suitable for doing.

  In this method, before forming the contact electrode 13 and the drive electrode 15, as described above with reference to FIG. 20B, the intermediate layer 103 is formed by wet etching using, for example, BHF as an etchant. (The movable part 12 is thereby released from the second layer 102). The sacrificial layer 111 formed so as to cover the contact electrode 13 and the drive electrode 15 in the step described above with reference to FIG. 21A is formed in the step described above with reference to FIG. It can be removed without performing a wet etching process using BHF as an etchant. Therefore, according to this method, the contact electrode 13 and the drive electrode 15 can be prevented from being exposed to a strong etching solution such as BHF. When the contact electrode 13 and the drive electrode 15 are exposed to a strong etching solution such as BHF, the contact electrode 13 and the drive electrode 15 are easily peeled from the first layer 101 or the movable portion 12.

  In addition, according to the present method using the protective film 110a on the contact electrode 13, a predetermined residue (for example, a residue derived from the resist pattern 105 or a residue derived from the sacrificial layer 111) adheres to the contact electrode 13. Can be prevented. This contributes to reducing the contact resistance between the contact electrodes 13 and 14.

  26 to 30 show a switching element X2 according to the second embodiment of the present invention. FIG. 26 is a plan view of the switching element X2, and FIG. 27 is a partially omitted plan view of the switching element X2. 28 to 30 are cross-sectional views taken along line XXVIII-XXVIII, line XXIX-XXIX, and line XXX-XXX in FIG.

  The switching element X2 includes a base substrate S2, a fixed portion 21, a movable portion 22, a contact electrode 23, a pair of contact electrodes 24A and 24B (not shown in FIG. 27), a drive electrode 25, and a drive electrode 26 (see FIG. 27).

  As shown in FIGS. 28 to 30, the fixing portion 21 is bonded to the base substrate S <b> 2 via the boundary layer 27. The fixing portion 21 is made of a silicon material such as single crystal silicon. It is preferable that the silicon material constituting the fixing portion 21 has a resistivity of 1000 Ω · cm or more. The boundary layer 27 is made of, for example, silicon dioxide.

  For example, as shown in FIG. 26, FIG. 27, or FIG. 30, the movable portion 22 has a fixed end 22a fixed to the fixed portion 21 and a free end 22b, and extends along the base substrate S2. It is surrounded by the fixing portion 21 through 28. The movable part 22 has an asymmetric shape. Such a movable part 22 is made of, for example, single crystal silicon.

  As shown well in FIG. 27, the contact electrode 23 is provided on the movable portion 22 near the free end 22b. The contact electrode 23 is made of a predetermined conductive material, and has, for example, a laminated structure including a Mo base film and an Au film thereon.

  As shown in FIG. 28 or FIG. 30, the contact electrodes 24 </ b> A and 24 </ b> B are erected on the fixed portion 21 and have protrusions 24 a and 24 b extending toward the contact electrode 13. The tip of the protrusion 24 a is in contact with the contact electrode 23. Each contact electrode 24A, 24B is connected to a predetermined circuit to be switched through a predetermined wiring (not shown). Au can be used as a constituent material of the contact electrodes 24A and 25B.

  The drive electrode 25 is provided over the movable portion 22 and the fixed portion 21 as shown well in FIG. As the constituent material of the drive electrode 25, the same constituent material as that of the contact electrode 23 can be employed.

  The drive electrode 26 is for generating an electrostatic attractive force (drive force) between the drive electrode 25, and as shown in FIG. 29, both ends thereof are joined to the fixed portion 21 to drive the drive electrode. It is erected so as to straddle the top of 25. The drive electrode 26 is grounded via a predetermined wiring (not shown). As the constituent material of the drive electrode 26, the same constituent material as that of the contact electrodes 24A and 24B can be employed.

  The drive electrodes 25 and 26 form an electrostatic drive mechanism in the switching element X2, and have a drive force generation region D on the movable portion 22, as shown in FIG. This driving force generation region D is a region facing the driving electrode 26 in the driving electrode 25 as shown well in FIG.

The switching element X2 has an asymmetry with respect to the shape of the movable portion 22, as clearly shown in FIG. Specifically, it passes through an imaginary line F ₁ (a point P ₁ that bisects the length of the fixed end 22 a of the movable portion 22 and a location C 1 that contacts the protrusion 24 a of the contact electrode 24 A in the contact electrode 23. ) So that the position of the center of gravity of the movable part 22 deviates relatively greatly. At the same time, the switching element X2 has asymmetry with respect to the arrangement of the driving force generation region D in the driving mechanism constituted by the driving electrodes 25 and 26. Specifically, an imaginary line F ₂ (a point P ₁ that bisects the length of the fixed end 22a of the movable portion 22; a location C2 that faces the projection 24b of the contact electrode 24B in the contact electrode 23; from between C1 2 passing through the point P ₂ to equal), as the center of gravity position O of the driving force generation region D deviates relatively large, the driving force generation region D is of having an asymmetrical shape.

  In such a switching element X2, when a potential is applied to the drive electrode 25, an electrostatic attractive force is generated between the drive electrodes 25 and 26. When the applied potential is sufficiently high, the movable portion 22 operates or elastically deforms until the contact electrode 23 contacts the protrusion 24b of the contact electrode 24B in a state where the contact electrode 23 contacts the protrusion 24a of the contact electrode 24A. In this way, the closed state of the switching element X2 is achieved. In the closed state, the pair of contact electrodes 24A and 24B are electrically bridged by the contact electrode 23, and current is allowed to pass between the contact electrodes 24A and 24B. By such a switch-on operation, for example, an on state of a high frequency signal can be achieved.

  On the other hand, in the switching element X2 in the closed state, when the electrostatic attraction acting between the drive electrodes 25 and 26 is extinguished by stopping the potential application to the drive electrode 25, the movable portion 22 returns to its natural state. The contact electrode 23 is separated from the protrusion 24b of the contact electrode 24B while being in contact with the protrusion 24a of the contact electrode 24A. In this way, the open state of the switching element X2 as shown in FIG. 28 is achieved. In the open state, the pair of contact electrodes 24A and 24B are electrically separated, and current is prevented from passing between the contact electrodes 24A and 24B. Such a switch-off operation can achieve, for example, an off state of a high-frequency signal. Further, the switching element X2 in such an open state can be switched again to the closed state or the on state by the switch-on operation described above.

  Thus, in the switching element X2 that operates substantially in a one-contact type, the contact electrode 23 and the protrusion 24a of the contact electrode 24A are always in contact with each other, so that the contact electrodes 24A and 24B (fixed contact electrodes) ) Variation in the orientation of the contact electrode 23 (movable contact electrode) can be suppressed. A small variation in the orientation of the contact electrode 23 with respect to the contact electrodes 24A and 24B contributes to reducing the drive voltage of the switching element X2.

  31 to 34 show a method for manufacturing the switching element X2 as a change in cross section corresponding to FIGS. FIGS. 35 to 37 show an enlarged view of the process in the vicinity of the protrusion forming portion in the manufacturing method.

  In this method, first, a material substrate S2 'as shown in FIG. The material substrate S <b> 2 ′ is an SOI (silicon on insulator) substrate and has a stacked structure including a first layer 201, a second layer 202, and an intermediate layer 203 therebetween. The configuration of the material substrate S2 'is the same as that of the material substrate S1' described above, for example. The first layer 201 is processed into the fixed portion 21 and the movable portion 22 described above. The second layer 202 is processed into the above-described base substrate S2. The intermediate layer 203 is processed into the boundary layer 27 described above.

  Next, as shown in FIG. 31B, a conductor film 204 and a protective film 205 are formed on the first layer 201. In forming the conductor film 204, for example, Cr is deposited on the first layer 201 by sputtering, and then Au is deposited thereon. The thickness of the Cr film is, for example, 50 nm, and the thickness of the Au film is, for example, 500 nm. The protective film 205 is formed by sputtering, for example, and is made of, for example, Cr, Mo, Ti, Ni, or an alloy containing these. The thickness of the protective film 205 is, for example, 500 nm.

  Next, as shown in FIG. 31C, resist patterns 206 and 207 are formed on the conductor film 204 by photolithography. The resist pattern 206 has a pattern shape corresponding to the contact electrode 23. The resist pattern 207 has a pattern shape corresponding to the drive electrode 25.

  Next, as shown in FIG. 32A, the conductive film 204 and the protective film 205 are etched using the resist patterns 206 and 207 as a mask, whereby the first layer 201 is formed. The contact electrode 23 and the protective film 205a thereon are formed, and the drive electrode 25 and the protective film 205b thereon are formed.

  Next, after removing the resist patterns 206 and 207, as shown in FIG. 32B, the first layer 201 is etched to form the slits 28. Next, as shown in FIG. Specifically, it is the same as the slit forming method described above with reference to FIG. 7B regarding the first manufacturing method of the switching element X1. In this step, the fixed portion 21 and the movable portion 22 are formed.

  Next, as shown in FIG. 32C, the first layer of the material substrate S2 ′ is formed so as to cover the movable portion 22, the contact electrode 23, the drive electrode 25, and the protective films 205a and 205b and close the slit 28. A sacrificial layer 208 is formed on the 201 side. For example, silicon dioxide can be used as the sacrificial layer material. As a method for forming the sacrificial layer 208, for example, a plasma CVD method or a sputtering method can be employed. The thickness of the sacrificial layer 208 to be formed is 5 μm, for example. Moreover, you may employ | adopt a polyimide as a sacrificial layer material.

  Next, by patterning the sacrificial layer 208, openings 208a and 208b are formed as shown in FIGS. 33A and 35A to partially expose the contact electrode 23, and FIG. Openings 208c, 208d, and 208e are formed as shown in FIG. Specifically, after a predetermined resist pattern is formed on the sacrificial layer 208 by a photolithography method, the sacrificial layer 208 is etched using the resist pattern as a mask. As an etching method, wet etching can be employed. As an etchant for wet etching, for example, buffered hydrofluoric acid (BHF) can be employed. The openings 208a and 208b are for forming the protrusions 24a and 24b of the contact electrodes 24A and 24B, respectively. The openings 208c and 208d are for exposing the regions where the contact electrodes 24A and 24B are joined in the fixed portion 21, respectively. The opening 208e is for exposing a region where the drive electrode 26 is joined in the fixed portion 21.

  Next, as shown in FIGS. 33B and 35B, the region exposed to the opening 208a of the sacrificial layer 208 in the protective film 205a is removed by wet etching. As the etching solution in this step, when the protective film 205a is made of Cr, for example, a ceric ammonium nitrate aqueous solution can be used. When the protective film 205a is made of Mo, for example, nitric acid and phosphoric acid are used. When the protective film 205a is made of Ti, for example, BHF can be used. When the protective film 205a is made of Ni, for example, phosphoric acid, nitric acid, and acetic acid are contained. An aqueous solution can be used.

  Next, the first seed layer 209a is formed over the portion exposed in the patterning step of the sacrificial layer 208 and the sacrificial layer 208, for example, as shown in FIG. (Omitted in FIG. 34). The first seed layer 209a is made of a material having good adhesion to the first layer 201 of the material substrate S2 ', and is made of, for example, Cr, Mo, Ti, Ni, or an alloy containing these. Such a first seed layer 209a is formed to a thickness of 1 μm by, for example, a sputtering method.

  Next, a second seed layer 209b is formed on the first seed layer 209a formed as described above, for example, as shown in FIG. 36A (in FIG. 33 and FIG. (Omitted). The second seed layer 209b is made of a material having good adhesion to the later-described plating forming portion. Such a second seed layer 209b can be formed, for example, by depositing Au having a thickness of 300 nm by a sputtering method. The second seed layer 209b and the first seed layer 209a described above form an energizing seed layer 209 that is used when the later-described electroplating method is executed.

  Next, as shown in FIGS. 33C and 36B, a resist pattern 210 is formed. The resist pattern 210 has openings 210a and 210b corresponding to the contact electrodes 24A and 24B and an opening 210c corresponding to the drive electrode 26.

  Next, as shown in FIGS. 34A and 36C, a contact electrode 24A having a protrusion 24a filling the opening 208a, a contact electrode 24B having a protrusion 24b filling the opening 208b, and a drive electrode 26 is formed. Specifically, for example, Au is grown by electroplating on the seed layer 209 exposed without being covered with the resist pattern 210. The thickness of the plating material to be grown is, for example, 20 μm.

  Next, as shown in FIG. 34B, after the resist pattern 210 is removed by, for example, wet etching, the exposed portions of the seed layer 209 (first seed layer 209a, second seed layer 209b) are, for example, Etching is removed as shown in FIG.

  Next, as shown in FIG. 34C or FIG. 37B, a part of the sacrificial layer 208 and the intermediate layer 203 is removed. Specifically, wet etching is performed on the sacrificial layer 208 and the intermediate layer 203. In this etching process, the sacrificial layer 208 is first removed, and then a part of the intermediate layer 203 is removed from the portion facing the slit 28. This etching process stops after an appropriate gap is formed between the entire movable portion 22 and the second layer 202. In this way, the boundary layer 27 remains in the intermediate layer 203. The second layer 202 constitutes the base substrate S2.

  Next, as shown in FIG. 37C, by wet etching, the protective films 205a and 205b and at least the seed layer 209 on the contact electrode 23 side surface of the protrusions 24a and 24B of the contact electrodes 24A and 24B The first seed layer 209a (removal target layers R3 and R4) on the contact electrode 23 side is removed. As a result, as shown in FIG. 37 (c), an air gap G3 is formed between the contact electrode 23 and the protrusion 24a of the contact electrode 24A, and between the contact electrode 23 and the protrusion 24b of the contact electrode 24B. An air gap G4 is formed therebetween. When the protective films 205a and 205b and the first seed layer 209a or the layers to be removed R3 and R4 are made of different materials, wet etching for the protective films 205a and 205b and wet etching for the first seed layer 209a are performed by different processes. In the case of the same material, wet etching for the protective films 205a and 205b and wet etching for the first seed layer 209a are performed in a single process. As the etching solution, when the protective films 205a and 205b and the first seed layer 209a are made of Cr, for example, a cerium ammonium nitrate aqueous solution can be used, and the protective films 205a and 205b and the first seed layer 209a When made of Mo, for example, an aqueous solution containing nitric acid and phosphoric acid can be used. When the protective films 205a, 205b and the first seed layer 209a are made of Ti, for example, BHF can be used, When the protective films 205a and 205b and the first seed layer 209a are made of Ni, for example, an aqueous solution containing phosphoric acid, nitric acid, and acetic acid can be used. Further, in this step, the removal target layers R3 and R4 which are part of the first seed layer 209a are appropriately removed, and then the contact electrodes 24A and 24B standing on the first layer 201 of the material substrate S2 ′. The etching time is adjusted so that the first seed layer 209a that forms the base end of the drive electrode 26 is not excessively eroded. Since the contact area of the contact electrodes 24A and 24B and the drive electrode 26 with respect to the first layer 201 is considerably larger than the size of the protrusions 24a and 24b, such adjustment is possible.

  After this step, the movable portion 22 is slightly warped, and the movable portion 22 is slightly displaced toward the contact electrode 24 (not shown). The drive electrode 25 formed as described above undergoes internal stress during the formation process, and the drive electrode 25 and the movable portion 22 to which the drive electrode 25 is joined are warped by the action of the internal stress. Specifically, the movable portion 22 is deformed or warped so that the free end 22 b of the movable portion 22 slightly approaches the contact electrode 24. The amount of displacement of the free end 22b and the contact electrode 23 due to the warpage is controlled with high accuracy by controlling the thickness of the drive electrode 25 formed on the movable portion 22 as described above. Can do.

  Thereafter, the entire device is dried by a supercritical drying method as necessary. As described above, the switching element X2 can be manufactured.

  This method substantially includes a first manufacturing method and a second manufacturing method of the switching element X1. This method is the same as that in which the first manufacturing method is easy to control the formation of the air gap between the contact electrodes 13 and 14 and is suitable for reducing the contact resistance as described above. It is easy to control the formation of an air gap between the electrodes 24A (protrusions 24a) (in this embodiment, it is controlled so that the air gap is finally eliminated), and it is suitable for reducing the contact resistance. For the same reason that the manufacturing method is easy to control the formation of the air gap between the contact electrodes 13 and 14 and is suitable for reducing the contact resistance as described above, the contact electrode 23 and the contact electrode 24B (protrusion 24b) are formed. It is easy to control the air gap formation between them and is suitable for reducing the contact resistance.

  In addition, according to the present method using the protective film 205a on the contact electrode 23, a predetermined residue (for example, a residue derived from the resist pattern 206 or a residue derived from the sacrificial layer 208) adheres to the contact electrode 23. Can be prevented. This contributes to reducing the contact resistance between the contact electrodes 23 and 24.

  In this method, as in the third manufacturing method of the switching element X1, the slit 28 is formed as described above with reference to FIG. 32B before the contact electrode 23 and the drive electrode 25 are formed. After forming and forming the fixed portion 21 and the movable portion 22, as described above with reference to FIG. 34C, a part of the intermediate layer 203 is removed by wet etching, and the entire movable portion 22 is formed. A gap may be formed between the second layer 202 and the second layer 202. Employing such a technique avoids exposing the contact electrode 23 and the drive electrode 25 to a strong etching solution such as BHF, substantially as described above with respect to the third manufacturing method of the switching element X1. be able to.

  FIG. 38 shows a partial configuration of a communication device 300 according to the third embodiment of the present invention. The communication device 300 includes a plurality of RF circuits C1 to Cm, a plurality of antennas A1 to Am, and a total of m switching elements 301 therebetween, and is configured as a mobile phone, for example.

  Each of the plurality of RF circuits C1 to Cm is a duplexer in the present embodiment, includes an LNA, a PA, and the like, and is connected to the baseband. Each of the RF circuits C1 to Cm is provided for each frequency band used by the communication device 300 for transmission and reception. The plurality of antennas A1 to Am are provided for each frequency band used by the communication device 300 for transmission and reception.

  Each switching element 301 is for switching the connection relationship between the plurality of RF circuits C1 to Cm and the plurality of antennas A1 to Am in accordance with the communication frequency, and one selected switching element 301 is necessary. Accordingly, control is performed so as to be in a closed state or an on state. Such a switching element 301 is configured by the switching element X1 obtained by any one of the first to third manufacturing methods described above or the switching element X2 manufactured as described above.

  By including the plurality of RF circuits C1 to Cm, the plurality of antennas A1 to Am, and the plurality of switching elements 301 as described above, the communication device 300 can support a plurality of systems in different frequency bands. It can operate as a multiband communication device.

  As a summary of the above, the configurations of the present invention and variations thereof are listed below as supplementary notes.

(Supplementary note 1) a first contact electrode;
A second contact electrode having a portion that includes a protrusion extending toward the first contact electrode and faces the first contact electrode, and
A method for manufacturing a switching element in which the first and second contact electrodes are provided so as to be in contact with each other,
Forming a first contact electrode on a substrate;
Forming a sacrificial layer covering the first contact electrode;
Patterning the sacrificial layer to form at least an opening that partially exposes the first contact electrode; and
Forming a seed layer composed of at least two layers on the portion exposed in the patterning step and on the sacrificial layer;
Forming a second contact electrode having a portion that includes a protrusion that faces the first contact electrode through the sacrificial layer and fills the opening;
Removing the sacrificial layer;
Removing at least the first contact electrode side layer of the seed layer on the first contact electrode side surface of the protrusion.
(Supplementary Note 2) Including the step of forming a protective film on the first contact electrode, and in the step of forming the opening, the sacrificial layer is patterned to form at least the protective film on the first contact electrode. The switching element manufacturing method according to appendix 1, including a step of removing the protective film after the step of exposing a part and removing the sacrificial layer.
(Appendix 3) a fixed part;
A movable part extending with a fixed end fixed to the fixed part;
A first contact electrode provided on the movable part;
A second contact electrode including a protrusion that extends toward the first contact electrode and has a portion facing the first contact electrode, the method comprising:
A first step of forming a first contact electrode on the first layer of the material substrate having a laminated structure including a first layer, a second layer, and an intermediate layer between the first and second layers;
A second step of forming the movable part in the first layer;
A third step of forming a sacrificial layer covering the movable part and the first contact electrode;
A fourth step of patterning the sacrificial layer to form at least an opening that partially exposes the first contact electrode;
A fifth step of forming a seed layer comprising at least two layers over the portion exposed in the fourth step and the sacrificial layer;
A sixth step of forming a second contact electrode having a projecting portion that faces the first contact electrode through the sacrificial layer and fills the opening;
A seventh step of removing the sacrificial layer;
An eighth step of removing an intermediate layer interposed between the second layer and the movable part;
A ninth step of removing at least the first contact electrode side layer of the seed layer on the first contact electrode side surface of the protrusion.
(Supplementary Note 4) The method includes a step of forming a protective film on the first contact electrode, and in the fourth step, the sacrificial layer is patterned to expose at least a part of the protective film on the first contact electrode. The switching element manufacturing method according to appendix 3, further comprising a step of removing the protective film after the seventh step.
(Supplementary note 5) a fixing part;
A movable part extending with a fixed end fixed to the fixed part;
A first contact electrode provided on the movable part;
A second contact electrode including a first protrusion extending toward the first contact electrode and having a portion facing the first contact electrode;
A third contact electrode including a second projecting portion extending toward the first contact electrode and having a portion facing the first contact electrode, the method comprising:
A first step of forming a first contact electrode on the first layer of the material substrate having a laminated structure including a first layer, a second layer, and an intermediate layer between the first and second layers;
A protective film forming step of forming a protective film on the first contact electrode;
A second step of forming the movable part in the first layer;
A third step of forming a sacrificial layer covering the movable part and the first contact electrode;
A fourth step of patterning the sacrificial layer to form at least a first opening and a second opening that at least partially expose the protective film on the first contact electrode;
A protective film part removing step of removing a region exposed to the first opening in the protective film;
A fifth step of forming a seed layer composed of at least two layers over the portion exposed in the fourth step and the protective film partial removal step and the sacrificial layer;
Forming a second contact electrode having a portion including a first protrusion that opposes the first contact electrode through the sacrificial layer and fills the first opening; and the second contact electrode through the sacrificial layer. Forming a third contact electrode having a portion including a second protrusion that opposes one contact electrode and fills the second opening; and
A seventh step of removing the sacrificial layer;
An eighth step of removing an intermediate layer interposed between the second layer and the movable part;
A ninth step of removing at least the first contact electrode side layer of the seed layer on the first contact electrode side surface of the first and second protrusions;
And a step of removing the protective film.
(Supplementary Note 6) Any one of Supplementary Notes 3 to 5, wherein the second step is performed before the first step, and the eighth step is performed after the second step and before the first step. The switching element manufacturing method as described in 2.
(Supplementary note 7) The switching element according to any one of Supplementary notes 1 to 6, wherein the lowermost layer and / or the protective film in the seed layer is made of chromium, molybdenum, titanium, nickel, or an alloy containing these. Production method.
(Supplementary note 8) The switching element manufacturing method according to any one of supplementary notes 1 to 7, wherein the sacrificial layer is made of polyimide.
(Supplementary note 9) A switching element manufactured by the method according to any one of supplementary notes 1 to 8.
(Additional remark 10) A communication apparatus provided with the switching element of Additional remark 9.

1 is a plan view of a switching element according to a first embodiment of the present invention. FIG. 2 is a partially omitted plan view of the switching element shown in FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 1. It is sectional drawing along line VV of FIG. 1 represents a part of the steps in the first manufacturing method of the switching element shown in FIG. The process following FIG. 6 is represented. The process following FIG. 7 is represented. The process following FIG. 8 is represented. A part of process of the protrusion formation location vicinity in a 1st manufacturing method is expanded and represented. The process after the process shown in FIG. The process after the process shown in FIG. 11 is expanded and represented. 2 represents a part of the steps in the second manufacturing method of the switching element shown in FIG. The process following FIG. 13 is represented. The process following FIG. 14 is represented. The process following FIG. 15 is represented. Part of the process in the vicinity of the protruding portion formation position in the second manufacturing method is shown in an enlarged manner. The process after the process shown in FIG. The process after the process shown in FIG. 18 is enlarged and shown. FIG. 4 illustrates some steps in the third manufacturing method of the switching element illustrated in FIG. 1. The process following FIG. 20 is represented. The process following FIG. 21 is represented. A part of process of the protrusion formation location vicinity in a 3rd manufacturing method is expanded and represented. The process after the process shown in FIG. The process after the process shown in FIG. 24 is enlarged and shown. It is a top view of a switching element concerning a 2nd embodiment of the present invention. FIG. 27 is a partially omitted plan view of the switching element shown in FIG. 26. FIG. 27 is a cross-sectional view taken along line XXVIII-XXVIII in FIG. FIG. 27 is a cross-sectional view taken along line XXIX-XXIX in FIG. 26. FIG. 27 is a cross-sectional view taken along line XXX-XXX in FIG. 26. FIG. 27 shows some steps in the method of manufacturing the switching element shown in FIG. 26. The process following FIG. 31 is represented. The process following FIG. 32 is represented. The process following FIG. 33 is represented. FIG. 27 shows a process in the vicinity of both protrusions in the method for manufacturing the switching element shown in FIG. The process after the process shown in FIG. 35 is expanded and shown. The process after the process shown in FIG. 36 is enlarged and shown. 4 illustrates a partial configuration of a communication device according to a third embodiment of the present invention. The partial structure of the conventional switching element is represented. FIG. 40 shows some steps in the method of manufacturing the switching element shown in FIG. 40 shows an enlarged view of the process in the vicinity of the protrusion forming portion in the manufacturing method shown in FIG.

Explanation of symbols

X1, X2, X3 Switching element S1, S2 Base substrate 11, 21 Fixed part 12, 22 Movable part 13, 14, 23, 24A, 24B, 92, 93 Contact electrode 14a, 24a, 24b Protrusion part 15, 16, 25, 26 Driving electrode 17, 27 Boundary layer 18, 28 Slit S1 ′, S2 ′ Material substrate 101, 201 First layer 102, 202 Second layer 103, 203 Intermediate layer 104, 204 Conductive film 107, 111, 208 Sacrificial layer 110, 110a, 110b, 205, 205a, 205b Protective film

Claims (8)

A first contact electrode;
A second contact electrode having a portion that includes a protrusion extending toward the first contact electrode and faces the first contact electrode, and
A method for manufacturing a switching element in which the first and second contact electrodes are provided so as to be in contact with each other,
Forming a first contact electrode on a substrate;
Forming a sacrificial layer covering the first contact electrode;
Patterning the sacrificial layer to form at least an opening that partially exposes the first contact electrode; and
Forming a seed layer composed of at least two layers on the portion exposed in the patterning step and on the sacrificial layer;
Forming a second contact electrode having a portion that includes a protrusion that faces the first contact electrode through the sacrificial layer and fills the opening;
Removing the sacrificial layer;
Removing at least the first contact electrode side layer of the seed layer on the first contact electrode side surface of the protrusion.   Forming a protective film on the first contact electrode, wherein the opening is formed by patterning the sacrificial layer to expose at least a part of the protective film on the first contact electrode. The method for manufacturing a switching element according to claim 1, further comprising a step of removing the protective film after the step of removing the sacrificial layer. A fixed part;
A movable part extending with a fixed end fixed to the fixed part;
A first contact electrode provided on the movable part;
A second contact electrode including a protrusion that extends toward the first contact electrode and has a portion facing the first contact electrode, the method comprising:
A first step of forming a first contact electrode on the first layer of the material substrate having a laminated structure including a first layer, a second layer, and an intermediate layer between the first and second layers;
A second step of forming the movable part in the first layer;
A third step of forming a sacrificial layer covering the movable part and the first contact electrode;
A fourth step of patterning the sacrificial layer to form at least an opening that partially exposes the first contact electrode;
A fifth step of forming a seed layer comprising at least two layers over the portion exposed in the fourth step and the sacrificial layer;
A sixth step of forming a second contact electrode having a projecting portion that faces the first contact electrode through the sacrificial layer and fills the opening;
A seventh step of removing the sacrificial layer;
An eighth step of removing an intermediate layer interposed between the second layer and the movable part;
A ninth step of removing at least the first contact electrode side layer of the seed layer on the first contact electrode side surface of the protrusion.   Forming a protective film on the first contact electrode, and in the fourth step, patterning the sacrificial layer to expose at least a part of the protective film on the first contact electrode; The method for manufacturing a switching element according to claim 3, further comprising a step of removing the protective film after seven steps. A fixed part;
A movable part extending with a fixed end fixed to the fixed part;
A first contact electrode provided on the movable part;
A second contact electrode including a first protrusion extending toward the first contact electrode and having a portion facing the first contact electrode;
A third contact electrode including a second projecting portion extending toward the first contact electrode and having a portion facing the first contact electrode, the method comprising:
A first step of forming a first contact electrode on the first layer of the material substrate having a laminated structure including a first layer, a second layer, and an intermediate layer between the first and second layers;
A protective film forming step of forming a protective film on the first contact electrode;
A second step of forming the movable part in the first layer;
A third step of forming a sacrificial layer covering the movable part and the first contact electrode;
A fourth step of patterning the sacrificial layer to form at least a first opening and a second opening that at least partially expose the protective film on the first contact electrode;
A protective film part removing step of removing a region exposed to the first opening in the protective film;
A fifth step of forming a seed layer composed of at least two layers over the portion exposed in the fourth step and the protective film partial removal step and the sacrificial layer;
Forming a second contact electrode having a portion including a first protrusion that opposes the first contact electrode through the sacrificial layer and fills the first opening; and the second contact electrode through the sacrificial layer. Forming a third contact electrode having a portion including a second protrusion that opposes one contact electrode and fills the second opening; and
A seventh step of removing the sacrificial layer;
An eighth step of removing an intermediate layer interposed between the second layer and the movable part;
A ninth step of removing at least the first contact electrode side layer of the seed layer on the first contact electrode side surface of the first and second protrusions;
And a step of removing the protective film.   6. The method according to claim 3, wherein the second step is performed before the first step, and the eighth step is performed after the second step and before the first step. Switching element manufacturing method.   The switching element manufacturing method according to claim 1, wherein the lowermost layer and / or the protective film in the seed layer is made of chromium, molybdenum, titanium, nickel, or an alloy containing these.   A switching element manufactured by the method according to claim 1.

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