JP2008155342A - Manufacturing method for micro structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily manufacture a movable structure with an insulating layer made of an inorganic material such as silicon oxide at a high yield by using a resin sacrifice layer. <P>SOLUTION: The metal sacrifice layer 107 is formed on the upper surfaces of a support member 105 and the first resin sacrifice layer 106, and then, a silicon oxide film is formed on the upper surface of the metal sacrifice layer 107 by a sputtering method. The insulating layer 108 is formed by means of a known photolithography technique and etching technique, and the movable structure including a plate-shaped upper electrode 111, beam section 112, and anchor section 113 is also formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a microstructure having a movable structure including an insulating layer made of an inorganic material such as silicon oxide.

  In recent years, micro electro mechanical system (MEMS) technology has been developed that performs microfabrication three-dimensionally using thin film formation technology, photolithography technology, and various etching technologies to produce micro structures such as microswitches ( Non-patent document 1). An example of such a fine structure is shown in FIG. 8A is a plan view, and FIGS. 8B and 8C are cross-sectional views taken along line bb in FIG. 8A. This microstructure includes two wirings 802 formed on the substrate 801 and the substrate 801, a lower electrode 803, a support member 807, a flexible beam 808 supported at one end by the support member 807, and a beam 808. An upper electrode 809 supported at the other end, an insulating layer 806 in contact with the lower surface of the upper electrode 809, and a contact electrode 805 in contact with the lower surface of the insulating layer 806, as a switch by contact / non-contact between the wiring 802 and the contact electrode 805 It has the function of

  For example, when a voltage is applied between the upper electrode 809 and the lower electrode 803, the upper electrode 809 is attracted to the lower electrode 803 by electrostatic attraction. The beam 808 is deformed by this force, and the switch is turned on when the contact electrode 805 contacts the two wirings 802 as shown in FIG. 8B. On the other hand, when the application of the voltage is stopped, the upper electrode 809 returns to the original position by the restoring force of the beam 808, the contact electrode 05 is separated from the wiring 802, and the switch is turned off. In this manner, a function as a switch is realized in the structure of FIG.

  Here, the insulating layer 806 insulates and separates the upper electrode 809 and the contact electrode 805, and in the ON state of the switch, the element is damaged due to a short circuit due to contact between the upper electrode 809 and the lower electrode 803 or fusion thereof. Plays an important role in preventing.

  Next, an outline of a manufacturing method using the conventional technique for the above-described microstructure will be briefly described with reference to FIG. First, as shown in FIG. 9A, a metal wiring 802 and a lower electrode 803 are formed on a substrate 801. Next, as shown in FIG. 9B, a sacrificial layer 804 is formed. Next, as shown in FIG. 9C, the sacrificial layer 804 above the wiring 802 is partially etched to form a recess 804a. Next, as shown in FIG. 9D, a contact electrode 805 is formed inside the recess 804a.

  Next, as shown in FIG. 9E, an insulating layer 806 is formed on the upper surfaces of the sacrificial layer 804 and the contact electrode 805. Next, as shown in FIG. 9F, a through hole 804b is formed in the sacrificial layer 804. Subsequently, as shown in FIG. 9G, a support portion 807, a beam 808, and an upper electrode 809 are formed. . Finally, as shown in FIG. 9H, the microstructure shown in FIG. 8 is formed by removing the sacrificial layer 804.

  As described above, in order to realize a microstructure having a movable function, a technique for forming a sacrificial layer and removing the sacrificial layer for forming a movable space is important. As the sacrificial layer, a silicon oxide film, a polycrystalline silicon, a metal material such as copper, and a resin material such as polyimide can be used. Among these, resin materials can be formed and removed at low temperatures, and can be formed in various film thicknesses, and can be patterned using photolithography technology by adding a photosensitizer. It has excellent characteristics. For this reason, the application of a sacrificial layer using a resin material is expected in the case of forming a fine structure that can be integrated with an LSI and forming the fine structure with fewer steps.

A.P.De Silva, et al., "Motorola MEMS Switch Technology for High Frequency Applications", Microelectromechanical System Conference, pp.22-24, Aug., 2001.

  However, when an insulating layer made of an inorganic insulating film such as a silicon oxide film is formed on the upper surface of the sacrificial layer made of resin in order to form a fine structure as shown in FIG. There was a problem that yield and reliability were lowered due to low adhesion and peeling of the film.

  As a method for improving the adhesion between different films, a method in which an adhesion layer using a metal film typified by titanium is sandwiched between two films having low adhesion is conventionally known. However, for the purpose of improving the adhesion between the sacrificial layer and the insulating layer as described above, when an adhesion layer made of a metal material is used, a conductive adhesion is provided on the lower surface of the insulating layer even after the sacrificial layer is removed. The layer remains. In this case, a short circuit occurs through the adhesion layer, and the adhesion layer shields the electric field between the upper electrode and the lower electrode, thereby impairing the function of the insulating layer.

  On the other hand, a method of etching away the adhesion layer remaining on the lower surface of the insulating layer after removing the sacrificial layer can be considered, but in this case, the insulating layer and the structure are also etched simultaneously with the adhesion layer. A problem occurs. In general, in the manufacture of a microstructure having a movable structure, it is necessary to leave the structure when the sacrificial layer is removed. When a resin is used as a sacrificial layer, other materials such as metal are sacrificed. The material used in the structure and the manufacturing process are greatly different from those in the case of using as a layer. In a microstructure that assumes the use of a resin as a sacrificial layer, if the metal sacrificial layer is removed using a normal metal removal process after the resin sacrificial layer is removed, the structure that should originally remain is removed. Occurs. For this reason, conventionally, it is not common to use both the resin sacrificial layer and the metal sacrificial layer. As described above, in the microstructure using the sacrificial layer made of resin, there is a problem that it is not easy to form an insulating layer on the sacrificial layer.

  The present invention has been made to solve the above-described problems, and a movable structure including an insulating layer made of an inorganic material such as silicon oxide can be easily increased using a sacrificial layer made of a resin. The purpose is to enable production by yield.

  The manufacturing method of the microstructure according to the present invention includes a first step in which a lower electrode and a support portion higher than the lower electrode are formed on a substrate, and an organic material so as to cover the lower electrode on the substrate. A second step in which a resin sacrificial layer is formed, a third step in which a metal sacrificial layer made of a metal selected from chromium and nickel is formed on the resin sacrificial layer, and a metal sacrificial layer A movable structure including a fourth step in which an insulating layer made of an inorganic material is formed in contact with the upper surface and an upper electrode disposed on the insulating layer is formed on the support portion and the insulating layer. And a sixth step of removing the resin sacrificial layer and the metal sacrificial layer by heat treatment in an ozone atmosphere. According to this manufacturing method, the upper electrode having the insulating layer on the surface on the substrate side is placed on the lower electrode at a predetermined distance.

  In the fine structure manufacturing method, the wiring is formed on the substrate before the second step, and the contact electrode is formed on the metal sacrificial layer above the wiring before the fourth step. Thereafter, an insulating layer may be formed on the contact electrode and the metal sacrificial layer. In this case, a recess may be formed in the resin sacrificial layer, and a contact electrode may be formed in the recess.

  In the fine structure manufacturing method, in the second step, the resin sacrificial layer is formed on the substrate so as to cover the lower electrode and the support portion, and then the resin sacrificial layer is patterned to support the substrate. An opening that exposes the upper surface of the part is formed in the resin sacrificial layer, and in the fifth step, the movable structure may be formed on the support part through the opening.

  As described above, according to the present invention, after the metal sacrificial layer made of a metal selected from chromium and nickel is formed on the resin sacrificial layer, the insulating layer made of an inorganic material comes into contact with the metal sacrificial layer. After the layer is formed and the movable structure including the upper electrode is formed thereon, the resin sacrificial layer and the metal sacrificial layer are removed by heat treatment in an ozone atmosphere. Therefore, an insulating layer is formed on the substrate side surface. The upper electrode provided is in a state of being arranged on the lower electrode at a predetermined distance. As described above, according to the present invention, it is possible to obtain an excellent effect that a movable structure including an insulating layer made of an inorganic material such as silicon oxide can be easily manufactured with a high yield using a resin sacrificial layer. It is done.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Embodiment 1]
First, a first embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, and FIG. 1 to 3 are process diagrams for explaining the manufacturing method of the fine structure according to the first embodiment. First, as shown in FIG. 1A, an interlayer insulating layer 102 made of, for example, silicon oxide is formed on a semiconductor substrate 101 made of, for example, silicon. The semiconductor substrate 101 may include a semiconductor integrated circuit composed of a plurality of transistors, resistors, capacitors, wirings, and the like. For example, a contact hole for electrically connecting to the wiring of the integrated circuit has interlayer insulation. It may be formed at a predetermined location of the layer 102.

  When such a semiconductor substrate 101 is prepared, the first seed layer 103 is formed on the interlayer insulating layer 102 as shown in FIG. The first seed layer 103 may be formed, for example, by first depositing titanium by sputtering or vapor deposition, and subsequently depositing gold thereon. The thickness of titanium may be about 0.1 μm, and the thickness of gold may be about 0.1 μm.

  Next, a resist material having photosensitivity is applied on the first seed layer 103, exposed using a mask (photomask) having a desired pattern, and developed to form a desired lower electrode. A resist pattern having an opening at a location is formed. Subsequently, a gold pattern is formed by electrolytic plating on the first seed layer 103 exposed at the opening of the resist pattern, and then the resist pattern is removed. As a result, the lower electrode 104 is formed on the first seed layer 103 as shown in FIG. The film thickness of the resist at this time is about 2 μm, and the film thickness of the gold pattern formed by plating may be about 1 μm.

  Next, a resist pattern is formed and a gold pattern is formed by a plating method in the same manner as the formation of the lower electrode 104 described above, whereby a support member 105 is formed around the lower electrode 104 as shown in FIG. Is formed. The lower electrode 104 and the support member 105 are in a state of being spaced apart. In forming the support member 105, the resist pattern may have a thickness of about 4 μm, and the gold pattern by plating may have a thickness of about 2 μm. By doing so, the support member 105 is formed higher than the lower electrode 104.

  Next, by etching away the first seed layer 103 using the lower electrode 104 and the support member 105 as a mask, the lower electrode 104 and the support member 105 are formed on the interlayer insulating layer 102 as shown in FIG. The state is electrically separated above. In the etching of the first seed layer 103, for example, the gold layer above the first seed layer 103 may be selectively removed by wet etching with an etching solution composed of iodine, ammonium iodide, water, and ethanol. . Next, the titanium layer under the first seed layer 103 exposed by this etching may be selectively removed by wet etching with a hydrogen fluoride aqueous solution.

  Next, as shown in FIG. 1E, the first resin sacrificial layer 106 is formed so as to cover the lower electrode 104 and the support member 105. The first resin sacrificial layer 106 is composed of a resin that is an organic material. For example, the first resin sacrificial layer 106 is obtained by adding a positive photosensitive agent to a base resin such as polyamide, polyamic acid, or polybenzoxazole (or a precursor thereof). Can be used, and can be formed by spin coating. As a positive photosensitive resin based on polybenzoxazole, for example, “CRC8300” manufactured by Sumitomo Bakelite Co., Ltd. is available.

  Next, as shown in FIG. 1 (f), the first resin sacrificial layer 106 on the support member 105 is removed, and a through hole 106 a is formed in the first resin sacrificial layer 106 to expose the upper surface of the support member 105. It will be in the state. By patterning the photosensitive first resin sacrificial layer 106 by a known lithography technique, the through hole 106a can be formed so that the upper surface of the support member 105 is exposed. When patterning (exposure / development) the first resin sacrificial layer 106, pre-baking (preheating) at 120 ° C. is performed for about 4 minutes as pre-processing, and heat processing at about 310 ° C. is performed after patterning to form a resin film. The (first resin sacrificial layer 106) is in a thermally cured state.

  Next, as shown in FIG. 2G, the metal sacrificial layer 107 is formed on the upper surface of the support member 105 and the first resin sacrificial layer 106. The metal sacrificial layer 107 is a layer made of chromium, and may be formed by depositing chromium by an evaporation method or the like. The thickness of the deposited chromium (metal sacrificial layer 107) may be about 0.1 μm.

  Next, as shown in FIG. 2H, the insulating layer 108 is formed on the upper surface of the metal sacrificial layer 107. The insulating layer 108 is made of an inorganic material such as a semiconductor oxide such as silicon or a metal oxide. For example, the insulating layer 108 may be formed by depositing a silicon oxide film by a sputtering method and processing it by a known photolithography technique and etching technique. The thickness of the deposited silicon oxide film may be about 0.6 μm. In the step of forming the insulating layer 108, the metal sacrificial layer 107 made of chromium is present, so that the insulating layer 108 can be formed with high adhesion.

  Next, as shown in FIG. 2I, the metal sacrificial layer 107 is selectively removed by etching using the insulating layer 108 as a mask. As is well known, the metal sacrificial layer 107 may be wet-etched with, for example, an aqueous solution of ceric ammonium nitrate. By this etching, the metal sacrificial layer 107 other than the lower region of the insulating layer 108 is removed.

  Next, as shown in FIG. 2J, the second resin sacrificial layer 109 is formed so that the upper surface of the insulating layer 108 is exposed and the upper surface of the support member 105 is exposed through the through hole 109a. State. The second resin sacrificial layer 109 may be formed in the same manner as the first resin sacrificial layer 106. For example, a photosensitive resin obtained by adding a positive photosensitive agent to a base resin such as polyamide, polyamic acid, or polybenzoxazole (or a precursor thereof) is applied by spin coating to form a coating film. At this time, a coating film is formed so that the lower surface unevenness by the insulating layer 108 is absorbed and the upper surface becomes flat, and then the coating film is etched by a predetermined amount to expose the upper surface of the insulating layer 108. State. In this state, the through-hole 109a may be formed by patterning a photosensitive coating film by a known lithography technique so that the upper surface of the support member 105 is exposed following the through-hole 106a. Alternatively, the coating film formed by spin coating may be patterned by a known lithography technique to form the through hole 109a and expose the upper surface of the insulating layer 108.

  Next, as shown in FIG. 2 (k), the second seed layer 110 is formed, and the movable structure including the plate-like upper electrode 111, the beam portion 112, and the anchor portion 113 is formed. To do. The second seed layer 110 may be formed in the same manner as the first seed layer 103. The second seed layer 110 may be formed by, for example, first depositing titanium by sputtering or vapor deposition, and subsequently depositing gold thereon. The thickness of titanium may be about 0.1 μm, and the thickness of gold may be about 0.1 μm.

  Further, the movable structure including the upper electrode 111, the beam portion 112, and the anchor portion 113 may be formed in the same manner as the lower electrode 104. For example, by applying a resist material on the second seed layer 110 and exposing it using a mask having a desired pattern, the upper electrode 111, the beam portion 112, the anchor portion 113, and the like are formed at desired locations. A resist pattern having an opening is formed, a gold pattern is formed by electrolytic plating on the second seed layer 110 exposed in the opening of the resist pattern, and then the resist pattern is removed. Accordingly, as shown in FIG. 2 (k), a movable structure including the upper electrode 111, the beam portion 112, and the anchor portion 113 may be formed on the second seed layer 110. . The resist pattern may have a thickness of about 2 μm, and the plating film may be formed in a thickness of about 1 μm. After forming the upper electrode 111, the beam portion 112, and the anchor portion 113 in this way, the second seed layer 110 is selectively etched away using these as a mask. The second seed layer 110 may be etched in the same manner as the first seed layer 103.

  Next, the second resin sacrificial layer 109, the first resin sacrificial layer 106, and the metal sacrificial layer 107 are removed by heat treatment in an ozone atmosphere. For example, the ozone may be brought into contact with the second resin sacrificial layer 109 and the first resin sacrificial layer 106 by heating to 250 to 300 ° C. in an ozone atmosphere, and these resin sacrificial layers may be incinerated. In this ozone treatment, the metal sacrificial layer 107 in contact with ozone is also removed by etching.

  By removing these, as shown in FIG. 3L, the insulating layer 108 and the upper electrode 111 are supported by the beam portion 112 and the anchor portion 113, and are disposed on the lower electrode 104 so as to face each other. As shown in the plan view of FIG. 3 (m), the upper electrode 111 is connected to the anchor portion 113 by beam portions 112 provided at four locations. The anchor portion 113 is disposed on the support member 105. Thus, the upper electrode 111 is supported on the semiconductor substrate 101 (interlayer insulating layer 102) by the beam portion 112, the anchor portion 113, and the support member 105.

  A pad terminal 114 is connected to the lower electrode 104, and a pad terminal 115 is connected to the upper electrode 111 via a beam portion 112, an anchor portion 113, and a support member 105. For example, the pad terminal 114 and the pad terminal 115 are connected to a wiring layer (not shown) provided under the interlayer insulating layer 102 via a contact hole (not shown). This is, for example, a MEMS variable capacitance element. When a DC bias voltage is applied between the lower electrode 104 and the upper electrode 111, the upper electrode 111 is bent and deformed toward the lower electrode 104 by an electrostatic force, and the distance between the electrodes changes. Therefore, the electrostatic capacitance between the lower electrode 104 and the upper electrode 111 changes depending on the bias voltage applied between both electrodes, and functions as a variable capacitance element controlled by the bias voltage.

  The beam portion 112 and the anchor portion 113 are for electrically connecting the upper electrode 111 and the pad terminal 115, and are preferably formed of a metal material having a small electric resistance. Further, the beam portion 112 and the anchor portion 113 may be formed of, for example, polysilicon or an inorganic insulating film other than a metal material. For example, electrical connection can be achieved by using polysilicon having a low resistance by introducing impurities at a high concentration. Further, even if the beam portion 112 and the anchor portion 113 are made of an insulating material, the above-described electrical connection may be obtained by providing wirings made of a metal material.

  Further, it is desirable that the upper electrode 111 be provided with a plurality of openings 121 that are sufficiently smaller than the area of the upper electrode 111 at every desired interval. In order for ozone, which is an etchant, to contact each sacrificial layer below the upper electrode 111 efficiently, the opening 121 is preferably provided. Note that if the side of the upper electrode 111 is open and the size of the upper electrode 111 is within twice the amount of lateral etching, the opening 121 may not be provided.

  As described above, the metal sacrificial layer 107 using a chromium film can be removed at the same time when the resin sacrificial layer is removed by exposure to an ozone atmosphere. As described above, since the metal sacrificial layer 107 does not exist in a state where the fine structure is completed, there are problems such as occurrence of a short circuit and shielding of an electric field between the upper electrode 111 and the lower electrode 104. Does not occur. Further, since the insulating layer 108 has high adhesion to the metal sacrificial layer 107, the insulating layer 108 can be formed with high yield without peeling of the film.

  In this fine structure manufacturing method, the metal sacrificial layer 107 is made of chromium. However, the present invention is not limited to this. For example, the metal sacrificial layer 107 may be formed of nickel. The metal sacrificial layer can be removed simultaneously with the important resin sacrificial layer by the treatment. Further, in the formation of the metal sacrificial rough 107 made of nickel, dilute hydrochloric acid or dilute nitric acid may be used as the nickel etching solution.

[Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIGS. 4, 5, 6, and 7. FIG. 4 to 7 are process diagrams for explaining the manufacturing method of the fine structure according to the second embodiment. First, as shown in FIG. 4A, an interlayer insulating layer 402 made of, for example, silicon oxide is formed on a semiconductor substrate 401 made of, for example, silicon. The semiconductor substrate 401 may include a semiconductor integrated circuit including a plurality of transistors, resistors, capacitors, wirings, and the like. For example, a contact hole for electrically connecting to the wiring of the integrated circuit has an interlayer insulation. The layer 402 may be formed at a predetermined location.

  When such a semiconductor substrate 401 is prepared, the first seed layer 403 is formed on the interlayer insulating layer 402 as shown in FIG. The first seed layer 403 may be formed by, for example, depositing titanium first and then depositing gold thereon by sputtering or vapor deposition. The thickness of titanium may be about 0.1 μm, and the thickness of gold may be about 0.1 μm.

  Next, a photosensitive resist material is applied on the first seed layer 403, exposed using a mask having a desired pattern, and developed, so that a wiring and a lower electrode are formed at desired locations. A resist pattern having an opening is formed. Subsequently, a gold pattern is formed by electrolytic plating on the first seed layer 403 exposed at the opening of the resist pattern, and then the resist pattern is removed, as shown in FIG. 4B. The wiring 404 and the lower electrode 405 are formed. The resist film thickness at this time may be about 2 μm, and the film thickness of the gold pattern formed by plating may be about 1 μm.

  Next, as shown in FIG. 5C, a support member 406 is formed around the lower electrode 405 by performing resist pattern formation and plating similarly to the formation of the wiring 404 and the lower electrode 405 described above. State. The lower electrode 405 and the support member 406 are arranged to be separated from each other. In forming the support member 406, the resist pattern may be about 4 μm thick and the gold pattern formed by plating may be about 2 μm thick. By doing so, the support member 405 is in a state of being formed higher than the wiring 404 and the lower electrode 405.

  Next, the first seed layer 403 is removed by etching using the wiring 404, the lower electrode 405, and the support member 406 as a mask, and as shown in FIG. 5D, the wiring 404, the lower electrode 405, and the support member 406 are formed. An electrically isolated state is formed on the interlayer insulating layer 402. In the etching of the first seed layer 403, for example, the gold layer above the first seed layer 403 may be selectively removed by wet etching with an etching solution composed of iodine, ammonium iodide, water, and ethanol. . Next, the titanium layer under the first seed layer 403 exposed by this etching may be selectively removed by wet etching with a hydrogen fluoride aqueous solution.

  Next, as illustrated in FIG. 5E, the first resin sacrificial layer 407 is formed so as to cover the wiring 404, the lower electrode 405, and the support member 406. The first resin sacrificial layer 407 is formed in a state where the film thickness of the region where the wiring 404 and the lower electrode 405 are disposed is thinner than the region where the support member 406 is disposed. The first resin sacrificial layer 407 is composed of a resin that is an organic material. For example, the first resin sacrificial layer 407 is obtained by adding a positive photosensitive agent to a base resin such as polyamide, polyamic acid, or polybenzoxazole (or a precursor thereof). Can be used, and can be formed by spin coating. As a positive photosensitive resin based on polybenzoxazole, for example, “CRC8300” manufactured by Sumitomo Bakelite Co., Ltd. is available.

  Next, as shown in FIG. 5 (f), the first resin sacrificial layer 407 at the top of the support member 406 is removed, and a through hole 407 a is formed in the first resin sacrificial layer 407 so that the upper surface of the support member 406 is exposed. It will be in the state. By patterning the photosensitive first resin sacrificial layer 407 by a known lithography technique, the through hole 407a can be formed so that the upper surface of the support member 406 is exposed. When patterning (exposure / development) the first resin sacrificial layer 407, pre-baking at 120 ° C. is performed for about 4 minutes as pre-processing, and heat processing at about 310 ° C. is performed after patterning to form a resin film (first resin). The sacrificial layer 407) is in a thermally cured state.

  Next, a resin layer similar to the first resin sacrificial layer 407 is formed on at least the region where the film thickness of the first resin sacrificial layer 407 is thin, and is patterned by a known lithography technique, so that FIG. As shown to (g), it is set as the state in which the 2nd resin sacrificial layer 408 provided with the recessed part 408a was formed. The recess 408 a is formed in a state of being disposed on the wiring 404. Even when the second resin sacrificial layer 408 is formed, a part of the front surface of the support member 406 is exposed through the through hole 407a. For example, when the resin layer is applied and formed over the entire area of the first resin sacrificial layer 407, the recess 408a may be formed by patterning, and an opening may be formed in the upper portion of the through hole 407a. .

  In the above description, the concave portion 408a is formed by forming the second resin sacrificial layer 408. However, the present invention is not limited to this. For example, a resist pattern having an opening in a recess formation region is formed on the first resin sacrificial layer 407, and the first resin sacrificial layer 407 is selectively etched using the resist pattern as a mask. A recess may be formed on the surface. In this case, the amount of selective etching of the first sacrificial layer 407 is controlled so that the upper surface of the wiring 404 is not exposed.

  Next, as shown in FIG. 5H, a metal sacrificial layer 409 is formed on the second resin sacrificial layer 408 including the exposed upper surface of the support member 406 and the inside of the recess 408a. . The metal sacrificial layer 409 is a layer made of chromium, and can be formed by depositing chromium by an evaporation method or the like. The film thickness of the deposited chromium (metal sacrificial layer 409) may be about 0.1 μm.

Next, as shown in FIG. 6I, a second seed layer 410 is formed, and a resist pattern is formed and plating is performed in the same manner as the formation of the wiring 404, whereby the contact electrode 411 is formed. To do. The second seed layer 410 may be formed, for example, by depositing gold by sputtering or vapor deposition, and the film thickness of gold may be about 0.1 μm. When the contact electrode 411 is formed, the resist pattern may have a thickness of about 2 μm and the plating film may have a thickness of about 0.5 μm. Further, the second seed layer 410 may be removed by etching using the contact electrode 411 formed by plating as a mask. The second seed layer 410 may be wet-etched with an etchant composed of iodine, ammonium iodide, water, and ethanol. According to this etching, the metal sacrificial layer 409 remains without being removed.
In the step of forming the contact electrode 411, the metal sacrificial layer 409 is present, and therefore the second seed layer 410 necessary for forming the contact electrode 411 is formed with high adhesion. Is possible.

  Next, as shown in FIG. 6J, an adhesive layer 412 made of, for example, titanium is formed on and around the upper surface of the contact electrode 411. The adhesion layer 412 may be formed by depositing titanium by a sputtering method, a vapor deposition method, or the like, and then processing the deposited titanium layer by a known photolithography technique and etching technique. The thickness of the deposited titanium may be about 0.1 μm, and the titanium may be removed by wet etching using a hydrogen fluoride aqueous solution.

  Next, as illustrated in FIG. 6K, the insulating layer 413 is formed on the metal sacrificial layer 409 so as to cover the adhesion layer 412. The insulating layer 413 may be formed so as to cover a region where the lower electrode 405 is formed. The insulating layer 413 is made of an inorganic material such as a semiconductor oxide such as silicon or a metal oxide. For example, the insulating layer 413 may be formed by depositing a silicon oxide film by a sputtering method and processing the deposited silicon oxide film by a known photolithography technique and etching technique. The film thickness of the silicon oxide film may be about 0.6 μm. By forming the silicon oxide film by using a sputtering method capable of forming a film at a relatively low temperature, the insulating layer 413 does not change the quality of the first resin sacrificial layer 407 and the second resin sacrificial layer 408 made of resin. Can be formed.

  In the above-described step of forming the insulating layer 413, the metal sacrificial layer 409 is present, so that the insulating layer 413 can be formed with high adhesion.

  Next, as shown in FIG. 6L, the metal sacrificial layer 409 is removed by etching using the insulating layer 413 as a mask. The metal sacrificial layer 409 may be wet etched with, for example, a ceric ammonium nitrate aqueous solution.

  Next, as shown in FIG. 6M, the third resin sacrificial layer 414 is formed so that the upper surface of the insulating layer 413 is exposed and the upper surface of the support member 406 is exposed through the through hole 414a. State. The third resin sacrificial layer 414 may be formed in the same manner as the first resin sacrificial layer 407 and the second resin sacrificial layer 408. For example, a photosensitive resin obtained by adding a positive photosensitive agent to a base resin such as polyamide, polyamic acid, or polybenzoxazole (or a precursor thereof) is applied by spin coating to form a coating film. At this time, a coating film is formed so that the lower surface unevenness by the insulating layer 413 is absorbed and the upper surface becomes flat, and then the coating film is etched by a predetermined amount, so that the upper surface of the insulating layer 413 is exposed. State. In this state, the through-hole 414a is formed by patterning a photosensitive coating film by a known lithography technique, and the upper surface of the support member 406 may be exposed after the through-hole 407a. Alternatively, the coating film formed by spin coating may be patterned by a known lithography technique to form the through hole 414a and to expose the upper surface of the insulating layer 413.

  Next, as shown in FIG. 7 (n), the third seed layer 415 is formed, and the movable structure including the plate-like upper electrode 416, the beam portion 417, and the anchor portion 418 is formed. To do. The third seed layer 415 may be formed in the same manner as the first seed layer 403, and the thickness of titanium may be about 0.1 μm and the thickness of gold may be about 0.1 μm.

  In addition, movable structures such as the upper electrode 416, the beam portion 417, and the anchor portion 418 may be formed in the same manner as the wiring 404. For example, by applying a resist material on the third seed layer 415 and exposing it using a mask having a desired pattern, the upper electrode 416, the beam portion 417, the anchor portion 418, and the like are formed at desired locations. A resist pattern having an opening is formed, a gold pattern is formed by electrolytic plating on the third seed layer 415 exposed in the opening of the resist pattern, and then the resist pattern is removed.

  As a result, as shown in FIG. 7 (n), a movable structure including the upper electrode 416, the beam portion 417, and the anchor portion 418 may be formed on the third seed layer 415. . The resist pattern may have a thickness of about 2 μm, and the plating film may be formed in a thickness of about 1 μm. After forming the upper electrode 416, the beam portion 417, and the anchor portion 418 in this way, the third seed layer 415 is selectively etched away using these as a mask. The third seed layer 415 may be etched in the same manner as the first seed layer 403.

  Next, the third resin sacrificial layer 414, the second resin sacrificial layer 408, the first resin sacrificial layer 407, and the metal sacrificial layer 409 are removed by heat treatment in an ozone atmosphere. For example, by heating to 250 to 300 ° C. in an ozone atmosphere, ozone is brought into contact with the third resin sacrificial layer 414, the second resin sacrificial layer 408, and the first resin sacrificial layer 407, and these resin sacrificial layers are ashed. That's fine. Further, in this ozone treatment, the metal sacrificial layer 409 in contact with ozone is also etched away, and a silicon oxide film as an insulator is exposed on the lower surface of the insulating layer 413. At the same time, the second seed layer 410 made of gold is exposed on the lower surface of the contact electrode 411.

  7 (o), the insulating layer 413 and the upper electrode 416 including the contact electrode 411 are supported by the beam portion 417 and the anchor portion 418, and are opposed to the wiring 404 and the lower electrode 405. Arranged state is obtained.

  Similar to the microstructure of the first embodiment described above, for example, the upper electrode 416 is connected to the anchor portion 418 by the beam portions 417 provided in four places in plan view. The anchor portion 418 is disposed on the support member 406. Thus, the upper electrode 416 is supported on the semiconductor substrate 401 (interlayer insulating layer 402) by the beam portion 417, the anchor portion 418, and the support member 406.

  Further, a pad terminal (not shown) is connected to the lower electrode 405, and a pad terminal (not shown) is connected to the upper electrode 416 via a beam part 417, an anchor part 418, and a support member 406. Two wirings 404 are provided across the position of the contact electrode 411. These pad terminals and wirings 404 are connected to a wiring layer (not shown) provided under the insulating layer 402 via a contact hole (not shown), for example.

  In the microstructure thus configured, when a DC bias voltage is applied between the lower electrode 405 and the upper electrode 416, the upper electrode 416 is bent and deformed toward the lower electrode 405 by electrostatic force, and two The contact electrode 411 is in contact with the wiring 404, and the two wirings 404 are electrically connected (ON state). Thus, the fine structure according to the second embodiment functions as a switch element.

  Note that the beam portion 417 and the anchor portion 418 are for electrically connecting the upper electrode 416 and a pad terminal (not shown), and are preferably formed of a metal material having a small electric resistance. Further, the beam portion 417 and the anchor portion 418 may be formed of, for example, polysilicon or an inorganic insulating film other than a metal material. For example, electrical connection can be achieved by using polysilicon having a low resistance by introducing impurities at a high concentration. Further, even if the beam portion 417 and the anchor portion 418 are made of an insulating material, the above-described electrical connection may be taken by providing wiring made of a metal material.

  The upper electrode 416 is preferably provided with a plurality of openings that are sufficiently smaller than the area of the upper electrode 416 for each desired interval. In order for ozone, which is an etchant, to contact each sacrificial layer below the upper electrode 416 efficiently, it is preferable to provide an opening. Note that if the side of the upper electrode 416 is open and the size of the upper electrode 416 is within twice the amount of lateral etching, the opening may not be provided.

  As described above, the metal sacrificial layer 409 using a chromium film can be removed at the same time when the resin sacrificial layer is removed by exposure to an ozone atmosphere. As described above, since the metal sacrificial layer 409 does not exist in a state where the fine structure is completed, there are problems such as occurrence of a short circuit and shielding of an electric field between the upper electrode 416 and the lower electrode 405. Does not occur. Further, since the second seed layer 410 made of gold on the surface of the contact electrode 411 is exposed, the contact resistance can be reduced. Further, since the second seed layer 410 and the insulating layer 413 have high adhesion to the metal sacrificial layer 409, there is no peeling of the film and the second seed layer 410 (contact electrode 411) and the high yield. The insulating layer 413 can be formed.

  In the method for manufacturing the microstructure, the metal sacrificial layer 409 is made of chromium. However, the present invention is not limited to this. For example, the metal sacrificial layer 409 may be formed of nickel. The metal sacrificial layer can be removed simultaneously with the important resin sacrificial layer by the treatment. In forming the metal sacrificial rough 409 made of nickel, dilute hydrochloric acid or dilute nitric acid may be used as the nickel etching solution.

It is process drawing for demonstrating the manufacturing method of the fine structure in Embodiment 1 of this invention. It is process drawing for demonstrating the manufacturing method of the fine structure in Embodiment 1 of this invention. It is process drawing for demonstrating the manufacturing method of the fine structure in Embodiment 1 of this invention. It is process drawing for demonstrating the manufacturing method of the fine structure in Embodiment 2 of this invention. It is process drawing for demonstrating the manufacturing method of the fine structure in Embodiment 2 of this invention. It is process drawing for demonstrating the manufacturing method of the fine structure in Embodiment 2 of this invention. It is process drawing for demonstrating the manufacturing method of the fine structure in Embodiment 2 of this invention. It is the top view (a) and sectional drawing (b), (c) which show the structure of the conventional fine structure. It is process drawing for demonstrating the manufacturing method of the existing fine structure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Semiconductor substrate, 102 ... Interlayer insulating layer, 103 ... 1st seed layer, 104 ... Lower electrode, 105 ... Support member, 106 ... Resin sacrificial layer, 106a ... Through-hole, 107 ... Metal sacrificial layer, 108 ... Insulating layer, DESCRIPTION OF SYMBOLS 109 ... Through-hole, 109a ... Through-hole, 110 ... 2nd seed layer, 111 ... Upper electrode, 112 ... Beam part, 113 ... Anchor part, 114, 115 ... Pad terminal, 121 ... Opening, 401 ... Semiconductor substrate, 402 ... Interlayer insulating layer, 403 ... first seed layer, 404 ... wiring, 405 ... lower electrode, 406 ... support member, 407 ... first resin sacrificial layer, 407a ... through hole, 408 ... second resin sacrificial layer, 408a ... concave, 409 ... metal sacrificial layer, 410 ... second seed layer, 411 ... contact electrode, 412 ... adhesion layer, 413 ... insulating layer, 414 ... third resin sacrificial layer 414, 414a ... through hole, 415 ... first Seed layer, 416 ... upper electrode, 417 ... beam portion, 418 ... anchor portion.

Claims (4)

A first step in which a lower electrode and a support portion higher than the lower electrode are formed on a substrate;
A second step in which a resin sacrificial layer made of an organic material is formed on the substrate so as to cover the lower electrode;
A third step in which a metal sacrificial layer made of a metal selected from chromium and nickel is formed on the resin sacrificial layer;
A fourth step in which an insulating layer made of an inorganic material is formed in contact with the metal sacrificial layer;
A fifth step in which a movable structure including an upper electrode disposed on the insulating layer is formed on the support and the insulating layer;
And a sixth step of removing the resin sacrificial layer and the metal sacrificial layer by heat treatment in an ozone atmosphere. In the manufacturing method of the fine structure according to claim 1,
Prior to the second step, a wiring is formed on the substrate,
Prior to the fourth step, a contact electrode was formed on the metal sacrificial layer above the wiring, and then the insulating layer was formed on the contact electrode and the metal sacrificial layer. A method for producing a fine structure, characterized in that a state is obtained. In the manufacturing method of the fine structure according to claim 2,
A method of manufacturing a fine structure, wherein a recess is formed in the resin sacrificial layer, and the contact electrode is formed in the recess. In the manufacturing method of the fine structure according to any one of claims 1 to 3,
In the second step,
The resin sacrificial layer is formed on the substrate so as to cover the lower electrode and the support, and then the resin sacrificial layer is patterned to expose the upper surface of the support Is formed on the resin sacrificial layer,
In the fifth step,
The method for manufacturing a microstructure is characterized in that the movable structure is formed on the support through the opening.

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