JP7120543B2 - Manufacturing method of MEMS element - Google Patents

Manufacturing method of MEMS element Download PDF

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JP7120543B2
JP7120543B2 JP2018155699A JP2018155699A JP7120543B2 JP 7120543 B2 JP7120543 B2 JP 7120543B2 JP 2018155699 A JP2018155699 A JP 2018155699A JP 2018155699 A JP2018155699 A JP 2018155699A JP 7120543 B2 JP7120543 B2 JP 7120543B2
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新一 荒木
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日清紡マイクロデバイス株式会社
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本発明は、ＭＥＭＳ素子に関し、特にトランスデューサ等の各種センサとして用いることができるＭＥＭＳ素子の製造方法に関する。 The present invention relates to a MEMS element, and more particularly to a method for manufacturing a MEMS element that can be used as various sensors such as transducers.

半導体プロセスを用いて形成されるＭＥＭＳ(Micro Electro Mechanical Systems)素子は、半導体基板上に可動電極、犠牲層および固定電極を形成した後、犠牲層の一部を除去することで、スペーサーを介して固定電極と可動電極との間にエアーギャップ（中空）構造が形成される。 A MEMS (Micro Electro Mechanical Systems) element formed using a semiconductor process forms a movable electrode, a sacrificial layer, and a fixed electrode on a semiconductor substrate. An air gap (hollow) structure is formed between the fixed electrode and the movable electrode.

例えば、容量型のＭＥＭＳ素子では、複数の貫通孔を備えた固定電極と、音圧等を受けて振動する可動電極とを対向して配置し、振動による可動電極の変位を電極間の容量変化として検出する構成となっている。この種のＭＥＭＳ素子は、例えば特許文献１に記載されている。 For example, in a capacitive MEMS element, a fixed electrode having a plurality of through-holes and a movable electrode that vibrates when receiving sound pressure or the like are placed facing each other. It is configured to be detected as A MEMS element of this type is described, for example, in Japanese Unexamined Patent Application Publication No. 2002-200013.

一般的なこの種のＭＥＭＳ素子の断面図を図９に示す。図９に示すように、支持基板となるシリコン基板２１上に熱酸化膜からなる絶縁膜２２を介して、可動電極２３と固定電極２４とがスペーサー２５を介して配置され、固定電極２４は全面を支持膜２６により支持されている。固定電極２４と支持膜２６には複数の貫通孔２７が形成されており、この貫通孔２７を介して音圧等を受けて可動電極２３が変位することで、固定電極２４と可動電極２３との間で形成されているキャパシタの容量値が変化する。この容量値を図示しない電極から取り出すことで、可動電極２３が受ける音圧等に応じた出力信号を得ることが可能となる。 FIG. 9 shows a cross-sectional view of a typical MEMS element of this type. As shown in FIG. 9, a movable electrode 23 and a fixed electrode 24 are arranged via spacers 25 on a silicon substrate 21 serving as a support substrate with an insulating film 22 made of a thermal oxide film interposed therebetween. are supported by the support film 26 . A plurality of through-holes 27 are formed in the fixed electrode 24 and the support film 26. When the movable electrode 23 is displaced by receiving sound pressure or the like through the through-holes 27, the fixed electrode 24 and the movable electrode 23 are displaced. The capacitance value of the capacitor formed between changes. By extracting this capacitance value from an electrode (not shown), it is possible to obtain an output signal corresponding to the sound pressure or the like received by the movable electrode 23 .

通常、固定電極２４は導電性ポリシリコン膜等で構成され、支持膜はシリコン窒化膜等で構成される。これらの膜は、一般的に自身が縮む方向に応力が働く引張応力を有し、シリコン窒化膜２８の引張応力は、導電性ポリシリコン膜２９の引張応力よりも大きい。このため、これらの膜を積層すると、図１０に模式的に示すように、導電性ポリシリコン膜２９側に凸形状となる反りを生じる。したがって、固定電極２４および支持膜２６は、図１１に示すように、可動電極２３側に凸形状となる反りを生じてしまう。このような固定電極２４の反りは、固定電極２４と可動電極２３との間隙を狭め、可動電極２３の可動域を制限し、ダイナミックレンジの狭小化を招いてしまう。 Normally, the fixed electrode 24 is composed of a conductive polysilicon film or the like, and the support film is composed of a silicon nitride film or the like. These films generally have a tensile stress acting in a direction in which they shrink, and the tensile stress of the silicon nitride film 28 is greater than the tensile stress of the conductive polysilicon film 29 . For this reason, when these films are laminated, a convex warp is generated on the conductive polysilicon film 29 side, as schematically shown in FIG. Therefore, as shown in FIG. 11, the fixed electrode 24 and the support film 26 are warped in a convex shape toward the movable electrode 23 side. Such warping of the fixed electrode 24 narrows the gap between the fixed electrode 24 and the movable electrode 23, restricts the movable range of the movable electrode 23, and causes a narrow dynamic range.

そこでこの問題を解決するため、支持膜に自身が拡がる方向に応力が働く圧縮応力を有する膜を積層することで、この膜の圧縮応力により支持膜の引張応力を緩和し、固定電極の反りの発生を抑制する技術が開示されている（特許文献２）。 Therefore, in order to solve this problem, by stacking a film having a compressive stress in the direction in which the supporting film itself expands, the compressive stress of this film relaxes the tensile stress of the supporting film and prevents the warp of the fixed electrode. A technique for suppressing the occurrence has been disclosed (Patent Document 2).

特開２０１１－０５５０８７号公報JP 2011-055087 A 特開２００７－３２４８０５号公報Japanese Patent Application Laid-Open No. 2007-324805

ところで、支持膜の引張応力を、圧縮応力をもつ膜を積層することで緩和し、固定電極の反りを抑制する方法は、所望の圧縮応力をもつ膜を形成する必要があり、制御性が低く、歩留まりが悪いという問題点があった。本発明は、このような問題点を解消し、簡便に固定電極の反りの発生を抑制することができるＭＥＭＳ素子の製造方法を提供することを目的とする。 By the way, the method of relaxing the tensile stress of the supporting film by stacking films with compressive stress and suppressing the warp of the fixed electrode requires forming a film with a desired compressive stress, and the controllability is low. , there was a problem that the yield was poor. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a MEMS element that can solve such problems and easily suppress the occurrence of warping of fixed electrodes.

上記目的を達成するため、本願請求項１に係る発明は、バックチャンバーを備えた基板上に、スペーサーを挟んで固定電極と可動電極とを配置したＭＥＭＳ素子の製造方法において、前記基板表面に絶縁膜を形成する工程と、該絶縁膜上に前記可動電極を形成する工程と、該可動電極上に、第１の犠牲層を形成する工程と、該第１の犠牲層上に前記固定電極を形成する工程と、該固定電極上に第２の犠牲層を形成する工程と、該第２の犠牲層上に支持膜を形成する工程と、前記支持膜、前記第２の犠牲層および前記固定電極を貫通する貫通孔であって、接続部形成予定領域の前記貫通孔の径を前記接続部形成予定領域以外の前記貫通孔の径より小さく形成する工程と、前記基板の一部をエッチング除去し、前記バックチャンバーを形成する工程と、前記貫通孔から前記第１の犠牲層の一部をエッチング除去し、前記スペーサーを形成し、前記固定電極と前記可動電極との間にエアーギャップを形成すると同時に、前記第２の犠牲層の一部を除去し、前記固定電極と前記支持膜の間であって径を小さく形成した前記貫通孔の周辺に前記接続部を形成する工程と、を含むことを特徴とする。 In order to achieve the above object, the invention according to claim 1 of the present application provides a method for manufacturing a MEMS element in which a fixed electrode and a movable electrode are arranged on a substrate provided with a back chamber with a spacer interposed therebetween, wherein forming an insulating film on the insulating film; forming the movable electrode on the insulating film; forming a first sacrificial layer on the movable electrode; forming an electrode; forming a second sacrificial layer on the fixed electrode; forming a support film on the second sacrificial layer; a step of forming a through-hole penetrating the fixed electrode, the diameter of the through-hole in the connection portion formation scheduled region being smaller than the diameter of the through-hole other than the connection portion formation scheduled region; etching away to form the back chamber; etching away a portion of the first sacrificial layer from the through hole to form the spacer, forming an air gap between the fixed electrode and the movable electrode; simultaneously with forming the second sacrificial layer, forming the connecting portion around the through hole formed between the fixed electrode and the supporting film and having a small diameter; characterized by comprising

本願請求項２に係る発明は、バックチャンバーを備えた基板上に、スペーサーを挟んで固定電極と可動電極とを配置したＭＥＭＳ素子の製造方法において、前記基板表面に絶縁膜を形成する工程と、該絶縁膜上に前記可動電極を形成する工程と、該可動電極上に、第１の犠牲層を形成する工程と、該第１の犠牲層上に前記固定電極を形成する工程と、該固定電極上に第２の犠牲層を形成する工程と、該第２の犠牲層上に支持膜を形成する工程と、接続部形成予定領域の前記支持膜および前記第２の犠牲層を除去し、接続部材を充填する工程と、前記支持膜、前記第２の犠牲層および前記固定電極を貫通する貫通孔を形成する工程と、前記基板の一部をエッチング除去し、前記バックチャンバーを形成する工程と、前記貫通孔から前記第１の犠牲層の一部をエッチング除去し、前記スペーサーを形成し、 前記固定電極と前記可動電極との間にエアーギャップを形成すると同時に、前記第２の犠牲層を除去し、前記固定電極と前記支持膜の間に前記接続部材からなる接続部を形成する工程と、を含むことを特徴とする。 The invention according to claim 2 of the present application is a method for manufacturing a MEMS element, in which a fixed electrode and a movable electrode are arranged on a substrate provided with a back chamber with a spacer interposed therebetween, wherein the step of forming an insulating film on the surface of the substrate; forming the movable electrode on the insulating film; forming a first sacrificial layer on the movable electrode; forming the fixed electrode on the first sacrificial layer; forming a second sacrificial layer on an electrode; forming a support film on the second sacrificial layer; removing the support film and the second sacrificial layer in a region where a connection portion is to be formed; filling a connection member ; forming a through hole penetrating through the support film, the second sacrificial layer and the fixed electrode; and etching away a portion of the substrate to form the back chamber. and removing part of the first sacrificial layer from the through hole by etching to form the spacer, forming an air gap between the fixed electrode and the movable electrode, and simultaneously removing the second sacrificial layer . and forming a connecting portion composed of the connecting member between the fixed electrode and the supporting film.

本発明のＭＥＭＳ素子の製造方法によるＭＥＭＳ素子は、固定電極と支持膜との間に間隙を有し、この間隙に固定電極と支持膜とを接続する接続部を配置して、固定電極を支持膜で支持する構造とすることで、固定電極の全面に支持層を積層することで生じる引張応力の影響を受けることが無く、固定電極が可動電極側に凸形状となる反りの発生を抑制することができる。 The MEMS element according to the method for manufacturing a MEMS element of the present invention has a gap between the fixed electrode and the support film, and the connection part for connecting the fixed electrode and the support film is arranged in the gap to support the fixed electrode. By adopting a structure in which the fixed electrode is supported by a film, it is not affected by the tensile stress generated by laminating the support layer on the entire surface of the fixed electrode, and the occurrence of warpage in which the fixed electrode is convex toward the movable electrode is suppressed. be able to.

また、本発明のＭＥＭＳ素子の製造方法によれば、接続部を形成する際、固定電極、第２の犠牲層および支持膜に形成する貫通孔の径を小さくすることで、固定電極と支持膜の間に第２の犠牲層を残留させることができるため、接続部を所望の位置に非常に簡便に形成することができる。 Further, according to the manufacturing method of the MEMS element of the present invention, when forming the connecting portion, by reducing the diameter of the through holes formed in the fixed electrode, the second sacrificial layer, and the support film, the fixed electrode and the support film are separated from each other. Since the second sacrificial layer can be left in between, the connection can be very easily formed at a desired position.

さらにまた、接続部を形成する際、接続部形成予定領域の支持膜および第２の犠牲層をエッチング除去し、接続部材を充填することでも形成できるため、制御性が非常に良く、接続部を所望の位置に所望の形状で簡便に形成することが可能となる。 Furthermore, when forming the connecting portion, the supporting film and the second sacrificial layer in the region where the connecting portion is to be formed can be removed by etching, and the connecting member can be filled. It is possible to easily form a desired shape at a desired position.

本発明の第１の実施例のＭＥＭＳ素子の製造工程を説明する図である。4A to 4C are diagrams for explaining a manufacturing process of the MEMS element of the first embodiment of the present invention; FIG. 本発明の第１の実施例のＭＥＭＳ素子の製造工程を説明する図である。4A to 4C are diagrams for explaining a manufacturing process of the MEMS device according to the first embodiment of the present invention; FIG. 本発明の第１の実施例のＭＥＭＳ素子の製造工程を説明する図である。4A to 4C are diagrams for explaining a manufacturing process of the MEMS device according to the first embodiment of the present invention; FIG. 本発明の第１の実施例のＭＥＭＳ素子の製造工程を説明する図である。4A to 4C are diagrams for explaining a manufacturing process of the MEMS device according to the first embodiment of the present invention; FIG. 本発明の第１の実施例のＭＥＭＳ素子の製造工程を説明する図である。4A to 4C are diagrams for explaining a manufacturing process of the MEMS device according to the first embodiment of the present invention; FIG. 本発明の第２の実施例のＭＥＭＳ素子の製造工程を説明する図である。It is a figure explaining the manufacturing process of the MEMS element of the 2nd Example of this invention. 本発明の第２の実施例のＭＥＭＳ素子の製造工程を説明する図である。It is a figure explaining the manufacturing process of the MEMS element of the 2nd Example of this invention. 本発明の第２の実施例のＭＥＭＳ素子の製造工程を説明する図である。It is a figure explaining the manufacturing process of the MEMS element of the 2nd Example of this invention. 従来のＭＥＭＳ素子を説明する図である。It is a figure explaining the conventional MEMS element. 従来のＭＥＭＳ素子を説明する図である。It is a figure explaining the conventional MEMS element. 従来のＭＥＭＳ素子を説明する図である。It is a figure explaining the conventional MEMS element.

本発明のＭＥＭＳ素子の製造方法によるＭＥＭＳ素子は、固定電極と支持膜との間に間隙を有し、この間隙に固定電極と支持膜とを接続する接続部を配置することで、固定電極を支持膜で支持する構造のため、固定電極の全面に支持層を積層することで生じる引張応力の影響を受けることが無く、固定電極が可動電極側に凸形状となる反りの発生を抑制することができる。以下、本発明のＭＥＭＳ素子の製造方法に従い、本発明の実施例について詳細に説明する。 The MEMS element according to the manufacturing method of the MEMS element of the present invention has a gap between the fixed electrode and the support film, and the connection portion for connecting the fixed electrode and the support film is arranged in the gap, whereby the fixed electrode is Due to the structure supported by the support film, the fixed electrode is not affected by the tensile stress generated by laminating the support layer on the entire surface of the fixed electrode, and the occurrence of warpage in which the fixed electrode is convex toward the movable electrode is suppressed. can be done. Examples of the present invention will now be described in detail according to the method for manufacturing a MEMS element of the present invention.

本発明の第１の実施例について、ＭＥＭＳ素子としてコンデンサマイクロフォンを例にとり、その製造工程に従い説明する。まず、結晶方位（１００）面の厚さ４２０μｍのシリコン基板１上に、厚さ１μｍ程度の熱酸化膜２（ＳｉＯ2）を形成する。その後、ＣＶＤ（Chemical Vapor Deposition）法により厚さ０．２～１．０μｍ程度の導電性ポリシリコン膜を積層形成する。次に通常のフォトリソグラフ法によりパターニングを行い、可動電極３を形成する。この可動電極３上に厚さ２～５μｍ程度のＵＳＧ(Undoped Silicate Glass)膜からなる第１の犠牲層４を積層する（図１）。 A first embodiment of the present invention will be described by taking a capacitor microphone as an example of a MEMS element and following its manufacturing process. First, a thermal oxide film 2 (SiO 2 ) having a thickness of about 1 μm is formed on a silicon substrate 1 having a crystal orientation (100) plane and a thickness of 420 μm. After that, a conductive polysilicon film having a thickness of about 0.2 to 1.0 μm is laminated by a CVD (Chemical Vapor Deposition) method. Next, patterning is performed by a normal photolithography method to form the movable electrode 3 . A first sacrificial layer 4 made of a USG (Undoped Silicate Glass) film having a thickness of about 2 to 5 μm is laminated on the movable electrode 3 (FIG. 1).

次に、第１の犠牲層４上に、厚さ１．１～３．０μｍ程度の導電性ポリシリコン膜を積層形成する。この導電性ポリシリコン膜を通常のフォトリソグラフ法によりパターニングした後、熱酸化を行い、厚さ０．１～１.０μｍ程度の導電性ポリシリコン膜からなる固定電極５と厚さ１～２μｍ程度の熱酸化膜からなる第２の犠牲層６を形成する。次に、全面に厚さ０．１～２．０μｍ程度のシリコン窒化膜からなる支持膜７を積層する（図２）。 Next, a conductive polysilicon film having a thickness of about 1.1 to 3.0 μm is laminated on the first sacrificial layer 4 . After patterning this conductive polysilicon film by a normal photolithographic method, it is thermally oxidized to form a fixed electrode 5 made of a conductive polysilicon film with a thickness of about 0.1 to 1.0 μm and a thickness of about 1 to 2 μm. Then, a second sacrificial layer 6 made of a thermal oxide film is formed. Next, a support film 7 made of a silicon nitride film having a thickness of about 0.1 to 2.0 μm is laminated on the entire surface (FIG. 2).

その後、固定電極５、第２の犠牲層６および支持膜７に、貫通孔８を形成し、犠牲層４を露出させる。ここで、後工程で固定電極５と支持膜７を接続する接続部を形成するため、径の小さな貫通孔８ａを、例えば、一例として、図３に示すように、中央部に形成する。 After that, a through hole 8 is formed in the fixed electrode 5 , the second sacrificial layer 6 and the support film 7 to expose the sacrificial layer 4 . Here, in order to form a connection portion for connecting the fixed electrode 5 and the support film 7 in a post-process, a through hole 8a having a small diameter is formed in the central portion as shown in FIG. 3, for example.

次に、シリコン基板１の裏面から熱酸化膜２が露出するまでシリコン基板１の一部を除去し、バックチャンバー９を形成する（図４）。 Next, a portion of the silicon substrate 1 is removed from the rear surface of the silicon substrate 1 until the thermal oxide film 2 is exposed to form a back chamber 9 (FIG. 4).

最後にエッチングによりバックチャンバー９内に露出する熱酸化膜２を除去するとともに、第１の犠牲層４の一部を除去し、スペーサー１０を介して固定電極５と可動電極３との間にエアーギャップ１１が形成される。また、このエッチングにより、貫通孔８、８ａ内に露出する第２の犠牲層６も除去されるが、中央の貫通孔８ａの径のみを小さく形成しているため、中央の貫通孔８ａは他の貫通孔８に比べてエッチング液の侵入量が少ない。さらに、中央の貫通孔８ａを除く隣り合う貫通孔８間は一定距離であるが、中央の貫通孔８ａと隣り合う貫通孔８との距離は、中央の貫通孔８ａを除く貫通孔８間の一定距離よりも長くなっている。このため、図５（ａ）および図５（ａ）のＡ－Ａ´面の断面図で固定電極５と接続部１２を図５（ｂ）に示すように、エッチングを行うと中央部にのみ第２の犠牲層が残留し、この残留した第２の犠牲層が固定電極５と支持膜７を接続する接続部１２となり、支持膜７の中央部で固定電極５を支持する形状となる。ここで、図５（ａ）および図５（ｂ）に示す接続体１２は６本の柱状体であるが、一部あるいはすべてが連結してもよい。つまり、接続体１２は少なくとも一つの柱状体であればく、その断面も円形とは限らない。 Finally, the thermal oxide film 2 exposed in the back chamber 9 is removed by etching, and a part of the first sacrificial layer 4 is removed. A gap 11 is formed. This etching also removes the second sacrificial layer 6 exposed in the through holes 8 and 8a. The penetration amount of the etchant is smaller than that of the through hole 8 of . Furthermore, the distance between the adjacent through holes 8 except the central through hole 8a is constant, but the distance between the central through hole 8a and the adjacent through holes 8 is longer than a certain distance. For this reason, as shown in FIG. 5(b), the fixed electrode 5 and the connection portion 12 are etched only in the central portion as shown in FIG. The second sacrificial layer remains, and this remaining second sacrificial layer serves as a connection portion 12 that connects the fixed electrode 5 and the support film 7, and has a shape in which the fixed electrode 5 is supported at the center portion of the support film 7. Here, although the connection bodies 12 shown in FIGS. 5(a) and 5(b) are six columnar bodies, some or all of them may be connected. In other words, the connection body 12 should be at least one columnar body, and its cross section is not necessarily circular.

図５（ａ）および図５（ｂ）に示す構造のＭＥＭＳ素子では、固定電極５と支持膜７との間に間隙１３を有し、この間隙１３に配置する接続部１２により支持膜７の中央部で固定電極５を支持する形状であるため、固定電極５の全面に支持膜７を積層することで生じる引張応力の影響を受けることが無く、固定電極５が可動電極３側に凸形状となる反りの発生を抑制することができる。 5(a) and 5(b) has a gap 13 between the fixed electrode 5 and the support film 7, and the support film 7 is separated by the connection portion 12 arranged in the gap 13. Since the shape supports the fixed electrode 5 at the central portion, the fixed electrode 5 is not affected by the tensile stress generated by laminating the support film 7 on the entire surface of the fixed electrode 5, and the fixed electrode 5 has a convex shape toward the movable electrode 3 side. It is possible to suppress the occurrence of warpage.

また、本実施例では、接続部を中央部に形成したものを一例として記載したが、中央部以外や複数か所に形成しても、固定電極が可動電極側に凸形状となる反りの発生を抑制することができる。ただし、この場合、接続部をバランスよく配置することが望ましい。 In addition, in the present embodiment, an example in which the connecting portion is formed in the central portion is described. can be suppressed. However, in this case, it is desirable to arrange the connecting portions in a well-balanced manner.

接続部を形成する際には、固定電極、第２の犠牲層および支持膜に形成する貫通孔の径を小さくすることで、固定電極と支持膜の間に第２の犠牲層を残留させることができるため、本実施例の接続部の形成方法により、接続部を形成する位置を限定されることもない。 When forming the connecting portion, the diameters of the through holes formed in the fixed electrode, the second sacrificial layer, and the supporting film are reduced so that the second sacrificial layer remains between the fixed electrode and the supporting film. Therefore, the position of forming the connecting portion is not limited by the method of forming the connecting portion of this embodiment.

次に、本発明の第２の実施例について説明する。まず、上記第１の実施例と同様、結晶方位（１００）面の厚さ４２０μｍのシリコン基板１上に、厚さ１μｍ程度の熱酸化膜２（ＳｉＯ2）を形成する。その後、ＣＶＤ法により厚さ０．２～１．０μｍ程度の導電性ポリシリコン膜を積層形成する。次に通常のフォトリソグラフ法によりパターニングを行い、可動電極３を形成する。この可動電極３上に厚さ２～５μｍ程度のＵＳＧ(Undoped Silicate Glass)膜からなる第１の犠牲層４を積層する（図１）。次に、第１の犠牲層４上に、厚さ１．１～３．０μｍ程度の導電性ポリシリコン膜を積層形成する。この導電性ポリシリコン膜を通常のフォトリソグラフ法によりパターニングした後、熱酸化を行い、厚さ０．１～１.０μｍ程度の導電性ポリシリコン膜からなる固定電極５と厚さ１～２μｍ程度の熱酸化膜からなる第２の犠牲層６を形成する。次に、全面に厚さ０．１～２．０μｍ程度のシリコン窒化膜からなる支持膜７を積層する（図２）。 Next, a second embodiment of the invention will be described. First, as in the first embodiment, a thermal oxide film 2 (SiO 2 ) having a thickness of about 1 μm is formed on a silicon substrate 1 having a crystal orientation (100) and a thickness of 420 μm. After that, a conductive polysilicon film having a thickness of about 0.2 to 1.0 μm is laminated by the CVD method. Next, patterning is performed by a normal photolithography method to form the movable electrode 3 . A first sacrificial layer 4 made of a USG (Undoped Silicate Glass) film having a thickness of about 2 to 5 μm is laminated on the movable electrode 3 (FIG. 1). Next, a conductive polysilicon film having a thickness of about 1.1 to 3.0 μm is laminated on the first sacrificial layer 4 . After patterning this conductive polysilicon film by a normal photolithographic method, it is thermally oxidized to form a fixed electrode 5 made of a conductive polysilicon film with a thickness of about 0.1 to 1.0 μm and a thickness of about 1 to 2 μm. Then, a second sacrificial layer 6 made of a thermal oxide film is formed. Next, a support film 7 made of a silicon nitride film having a thickness of about 0.1 to 2.0 μm is laminated on the entire surface (FIG. 2).

その後、通常のフォトリソグラフ法によりパターニングし、接続部形成予定領域の支持膜７および第２の犠牲層６をエッチング除去し、固定電極５を露出させる。ここで、接続部形成予定領域は後工程で形成する貫通孔と重ならない配置とする。エッチング除去した接続部形成予定領域内を充填し、支持膜７上に表面が平坦化されたポリシリコンからなる接続部材を形成した後、エッチバックし、支持膜７を露出することで、接続部形成予定領域内に選択的に接続部材を充填することができる。この接続部材が接続部１４となる（図６）。 After that, patterning is performed by a normal photolithographic method to etch away the support film 7 and the second sacrificial layer 6 in the area where the connection portion is to be formed, thereby exposing the fixed electrode 5 . Here, the connection portion formation planned region is arranged so as not to overlap with the through hole to be formed in a later step. After filling the region where the connecting portion is to be formed which has been removed by etching, and forming a connecting member made of polysilicon having a planarized surface on the supporting film 7, the supporting film 7 is etched back to expose the connecting portion. The connection member can be selectively filled in the formation scheduled region. This connecting member becomes the connecting portion 14 (FIG. 6).

次に、固定電極５、第２の犠牲層６および支持膜７を貫通する貫通孔８を形成し、第１の犠牲層４を露出させる。ここで貫通孔８の径は、上記第１の実施例と異なり、一定であることが好ましい。その後、シリコン基板１の裏面から熱酸化膜２が露出するまでシリコン基板１の一部を除去し、バックチャンバー９を形成する（図７）。 Next, a through hole 8 is formed through the fixed electrode 5 , the second sacrificial layer 6 and the support film 7 to expose the first sacrificial layer 4 . Here, unlike the first embodiment, the diameter of the through hole 8 is preferably constant. After that, a part of the silicon substrate 1 is removed from the rear surface of the silicon substrate 1 until the thermal oxide film 2 is exposed to form a back chamber 9 (FIG. 7).

最後にエッチングによりバックチャンバー９内に露出する熱酸化膜２を除去するとともに、第１の犠牲層４の一部および貫通孔８内に露出する第２の犠牲層６を除去する。その結果、図８に示すように、スペーサー１０を介して固定電極５と可動電極３との間にエアーギャップ１１が形成されるとともに、固定電極５と支持膜７が接続部１４で接続され、支持膜７の中央部で固定電極５を支持する形状となる。ここで、接続部は例えば円柱体や多角形柱体などでもよく、柱状体であればよい。 Finally, the thermal oxide film 2 exposed in the back chamber 9 is removed by etching, and a portion of the first sacrificial layer 4 and the second sacrificial layer 6 exposed in the through hole 8 are removed. As a result, as shown in FIG. 8, an air gap 11 is formed between the fixed electrode 5 and the movable electrode 3 via the spacer 10, and the fixed electrode 5 and the support film 7 are connected at the connection portion 14. The support film 7 has a shape in which the fixed electrode 5 is supported at the central portion thereof. Here, the connecting portion may be, for example, a columnar body or a polygonal columnar body, as long as it is a columnar body.

図８に示す構造のＭＥＭＳ素子では、第１の実施例と同様に、固定電極５と支持膜７との間に間隙１３を有し、この間隙１３に配置した接続部１３により支持膜７の中央部で固定電極５を支持する形状であるため、固定電極５の全面に支持膜７を積層することで生じる引張応力の影響を受けることが無く、固定電極５が可動電極３側に凸形状となる反りの発生を抑制することができる。 The MEMS element having the structure shown in FIG. 8 has a gap 13 between the fixed electrode 5 and the support film 7, as in the first embodiment. Since the shape supports the fixed electrode 5 at the central portion, it is not affected by the tensile stress generated by laminating the support film 7 on the entire surface of the fixed electrode 5, and the fixed electrode 5 has a convex shape toward the movable electrode 3 side. It is possible to suppress the occurrence of warpage.

また、本実施例では、接続部を中央部に２つ配置したものを一例として記載したが、少なくとも１つ配置すればよく、中央部以外に複数配置してもよい。ただし、この場合、接続部をバランスよく配置することが望ましい。 In addition, in this embodiment, two connecting portions are arranged in the central portion as an example, but at least one connecting portion may be arranged, and a plurality of connecting portions may be arranged other than in the central portion. However, in this case, it is desirable to arrange the connecting portions in a well-balanced manner.

さらにまた、接続部は通常のフォトリソグラフ法によりパターニングし、接続部形成予定領域の支持膜７および第２の犠牲層６をエッチング除去し、接続部材を充填することで形成できるため、制御性が非常に良く、所望の位置に所望の形状の接続部を簡便に形成することが可能となる。 Furthermore, the connecting portion can be formed by patterning by a normal photolithographic method, etching away the supporting film 7 and the second sacrificial layer 6 in the region where the connecting portion is to be formed, and filling the connecting member, thereby improving the controllability. It is very good, and it is possible to easily form a connecting portion having a desired shape at a desired position.

以上本発明の実施例について説明したが、本発明は上記実施例に限定されるものでないことは言うまでもない。例えば、固定電極５と支持膜７とが端部で直接接続する構造を記載したが、必ずしもその構造である必要はなく、接続部により支持膜が固定電極の端部付近を支持していればよく固定電極と支持膜の端部が直接接続しない構造であってもよい。 Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above embodiments. For example, although the structure in which the fixed electrode 5 and the support film 7 are directly connected at the end portion is described, this structure is not necessarily required, and the connection portion may support the support film near the end portion of the fixed electrode. A structure in which the fixed electrode and the end of the support membrane are not directly connected may be employed.

１、２１：シリコン基板、２、２２：熱酸化膜、３、２３：可動電極、４：第１の犠牲層、５、２４：固定電極、６：第２の犠牲層、７、２６：支持膜、８、８ａ、２７：貫通孔、９：バックチャンバー、１０、２５：スペーサー、１１：エアーギャップ、１２、１４：接続部、１３：間隙、２８：シリコン窒化膜、２９：導電性ポリシリコン膜 1, 21: Silicon substrate, 2, 22: Thermal oxide film, 3, 23: Movable electrode, 4: First sacrificial layer, 5, 24: Fixed electrode, 6: Second sacrificial layer, 7, 26: Support Film, 8, 8a, 27: through hole, 9: back chamber, 10, 25: spacer, 11: air gap, 12, 14: connection part, 13: gap, 28: silicon nitride film, 29: conductive polysilicon film

Claims (2)

バックチャンバーを備えた基板上に、スペーサーを挟んで固定電極と可動電極とを配置したＭＥＭＳ素子の製造方法において、
前記基板表面に絶縁膜を形成する工程と、
該絶縁膜上に前記可動電極を形成する工程と、
該可動電極上に、第１の犠牲層を形成する工程と、
該第１の犠牲層上に前記固定電極を形成する工程と、
該固定電極上に第２の犠牲層を形成する工程と、
該第２の犠牲層上に支持膜を形成する工程と、
前記支持膜、前記第２の犠牲層および前記固定電極を貫通する貫通孔であって、接続部形成予定領域の前記貫通孔の径を前記接続部形成予定領域以外の前記貫通孔の径より小さく形成する工程と、
前記基板の一部をエッチング除去し、前記バックチャンバーを形成する工程と、
前記貫通孔から前記第１の犠牲層の一部をエッチング除去し、前記スペーサーを形成し、
前記固定電極と前記可動電極との間にエアーギャップを形成すると同時に、前記第２の犠牲層の一部を除去し、前記固定電極と前記支持膜の間であって径を小さく形成した前記貫通孔の周辺に前記接続部を形成する工程と、を含むことを特徴とするＭＥＭＳ素子の製造方法。 In a method for manufacturing a MEMS element in which a fixed electrode and a movable electrode are arranged with a spacer interposed on a substrate provided with a back chamber,
forming an insulating film on the surface of the substrate;
forming the movable electrode on the insulating film;
forming a first sacrificial layer on the movable electrode;
forming the fixed electrode on the first sacrificial layer;
forming a second sacrificial layer on the fixed electrode;
forming a support film on the second sacrificial layer;
A through hole passing through the support film, the second sacrificial layer, and the fixed electrode, wherein the diameter of the through hole in the connection portion formation scheduled region is smaller than the diameter of the through hole other than the connection portion formation scheduled region. forming;
etching away a portion of the substrate to form the back chamber;
etching away a portion of the first sacrificial layer from the through hole to form the spacer;
At the same time as forming an air gap between the fixed electrode and the movable electrode, a part of the second sacrificial layer is removed, and the through hole is formed between the fixed electrode and the support film with a small diameter. and forming the connecting portion around the hole . バックチャンバーを備えた基板上に、スペーサーを挟んで固定電極と可動電極とを配置したＭＥＭＳ素子の製造方法において、
前記基板表面に絶縁膜を形成する工程と、
該絶縁膜上に前記可動電極を形成する工程と、
該可動電極上に、第１の犠牲層を形成する工程と、
該第１の犠牲層上に前記固定電極を形成する工程と、
該固定電極上に第２の犠牲層を形成する工程と、
該第２の犠牲層上に支持膜を形成する工程と、
接続部形成予定領域の前記支持膜および前記第２の犠牲層を除去し、接続部材を充填する工程と、
前記支持膜、前記第２の犠牲層および前記固定電極を貫通する貫通孔を形成する工程と、
前記基板の一部をエッチング除去し、前記バックチャンバーを形成する工程と、
前記貫通孔から前記第１の犠牲層の一部をエッチング除去し、前記スペーサーを形成し、 前記固定電極と前記可動電極との間にエアーギャップを形成すると同時に、前記第２の犠牲層を除去し、前記固定電極と前記支持膜の間に前記接続部材からなる接続部を形成する工程と、を含むことを特徴とするＭＥＭＳ素子の製造方法。 In a method for manufacturing a MEMS element in which a fixed electrode and a movable electrode are arranged with a spacer interposed on a substrate provided with a back chamber,
forming an insulating film on the surface of the substrate;
forming the movable electrode on the insulating film;
forming a first sacrificial layer on the movable electrode;
forming the fixed electrode on the first sacrificial layer;
forming a second sacrificial layer on the fixed electrode;
forming a support film on the second sacrificial layer;
a step of removing the support film and the second sacrificial layer in the region where a connection portion is to be formed, and filling the connection member;
forming a through hole penetrating through the support film, the second sacrificial layer and the fixed electrode;
etching away a portion of the substrate to form the back chamber;
Etching away a portion of the first sacrificial layer from the through hole to form the spacer, forming an air gap between the fixed electrode and the movable electrode, and simultaneously removing the second sacrificial layer. and forming a connecting portion composed of the connecting member between the fixed electrode and the supporting film.
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JP2018058150A (en) 2016-10-04 2018-04-12 新日本無線株式会社 Mems element and manufacturing method thereof

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