JP2009136934A - Manufacturing method of mems device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of MEMS (Micro Electro Mechanical System) devices capable of self-controllingly removing a sacrifice layer. <P>SOLUTION: This manufacturing method of MEMS devices 50 is characterized in, at first, forming a first sacrifice layer 52a consisting of aluminum or aluminum alloy on a first silicon oxide film 51, wherein the first sacrifice layer 52a is formed simultaneously with the formation of a gate electrode, and nextly, forming a second sacrifice layer 52b consisting of ITO (Indium Tin Oxide) on the first sacrifice layer 52a, wherein the second sacrifice layer 52b is formed simultaneously with the formation of a pixel electrode. A second silicon oxide film 53 and a silicon film 54 functioned as a weight 58 are formed on the sacrifice layer 52 and patterned into a predetermined shape. After that, aqua regia is brought into contact with the sacrifice layer 52 using the electrolytic corrosion reaction to self-controllingly remove the sacrifice layer 52 and form a cavity in the lower part of the weight 58. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a MEMS device including a movable object that is movably disposed on a substrate.

  The above-mentioned MEMS (Micro Electro Mechanical System) device is formed by utilizing a microfabrication technique, and is used, for example, as an acceleration sensor or a gyro sensor. Specifically, the MEMS device has a structure in which a movable object is arranged in a movable state on a substrate using a semiconductor process (for example, a weight is movably supported by a beam).

  Specifically, for example, as described in Patent Document 1, a sacrificial layer to be removed later is formed on a substrate, and a film to be left on the sacrificial layer is formed. The sacrificial layer is, for example, a silicon oxide film. The film functions as a weight (movable object), and is, for example, a silicon film.

  Then, the sacrificial layer is removed using an etching solution (for example, hydrofluoric acid) to form a cavity, so that the weight is supported by the beam made of a film and is in a floating state. The floated film is caused to function as a movable weight. Specifically, by detecting the fluctuation of the weight, for example, the acceleration, the moving direction, and the like are obtained.

JP 2007-165583 A

  However, the etching solution remains in the cavity after removing the sacrificial layer due to surface tension, whereby the film functioning as a weight is attracted by the etching liquid, and the film and the substrate are in close contact (sticking). Thereby, there exists a problem that a weight stops moving. In addition, there is a problem that the etching solution is difficult to enter the gap. In order to avoid such a problem, if the height of the cavity is increased, the etching processing time becomes longer. In addition, when vapor phase etching is used, there is a problem that usable materials are limited.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A method of manufacturing a MEMS device according to this application example includes a step of forming a sacrificial layer that causes an galvanic reaction on a substrate, a step of forming a functional film on the sacrificial layer, and a step of forming the sacrificial layer. Removing by using the galvanic reaction and forming a cavity under the functional film.

  According to this method, since the sacrificial layer can be removed (eroded) in a self-controlling manner by using the electrolytic corrosion reaction, the etching solution is formed in the hollowed area after the sacrificial layer is removed. It becomes possible to suppress sticking. Therefore, it can be prevented that the functional film is attracted by the etching solution and the substrate and the functional film are closely adhered (sticking). As a result, the space below the functional film can be hollowed out. In addition, since the electrolytic corrosion reaction is used, the sacrificial layer having a slight thickness can be removed, and the etching processing time can be shortened.

  Application Example 2 In the method of manufacturing a MEMS device according to the application example, the functional film is movably supported.

  According to this method, since the functional film is movably supported on the periphery, the functional film can be functioned as a movable film by hollowing out the lower side of the functional film.

  Application Example 3 In the MEMS device manufacturing method according to the application example, it is preferable that the sacrificial layer includes aluminum or an aluminum-based alloy and an ITO alloy.

  According to this method, since an aluminum or aluminum-based alloy and an ITO alloy are used, for example, a MEMS device can be manufactured together with the manufacture of an electro-optical device such as a liquid crystal device. Therefore, a MEMS device can be efficiently manufactured without preparing a new material.

  Application Example 4 In the method for manufacturing a MEMS device according to the application example, it is preferable that the aluminum or the aluminum-based alloy is formed simultaneously with the gate electrode.

  According to this method, since one of the sacrificial layers can be formed simultaneously with the gate electrode, the MEMS device can be efficiently manufactured without providing a dedicated manufacturing process.

  Application Example 5 In the method for manufacturing a MEMS device according to the application example, it is preferable that the aluminum or the aluminum-based alloy is formed at the same time as the source electrode or the drain electrode.

  According to this method, since one of the sacrificial layers can be formed simultaneously with the source electrode or the drain electrode, the MEMS device can be efficiently manufactured without providing a dedicated manufacturing process.

  Application Example 6 In the MEMS device manufacturing method according to the application example, it is preferable that the aluminum or the aluminum-based alloy is formed simultaneously with the reflective electrode.

  According to this method, since one of the sacrificial layers can be formed simultaneously with the reflective electrode, the MEMS device can be efficiently manufactured without providing a separate dedicated manufacturing process.

  Application Example 7 In the MEMS device manufacturing method according to the application example, it is preferable that the ITO alloy is formed simultaneously with the pixel electrode.

  According to this method, since one of the sacrificial layers can be formed simultaneously with the pixel electrode, a MEMS device can be efficiently manufactured without providing a dedicated manufacturing process.

  Application Example 8 In the MEMS device manufacturing method according to the application example, it is preferable that the functional film functions as a weight supported by a beam and is used as a part of a sensor.

  According to this method, since the functional film is used as a movable weight for detecting the direction, acceleration, and the like, the weight is bent (varied) by hollowing out the lower side of the functional film by an electrolytic corrosion reaction. And can function effectively as a sensor.

  Application Example 9 In the method of manufacturing a MEMS device according to the application example described above, the surface of the substrate in contact with the sacrificial layer or the film formed on the substrate is roughened before the step of forming the sacrificial layer. Is preferred.

  According to this method, the surface of the substrate or film in contact with the sacrificial layer is subjected to roughening treatment, whereby the etching solution can be easily separated, and the substrate or film and the functional film are in close contact (sticking). ) Can be suppressed.

  FIG. 1 is a schematic cross-sectional view illustrating a configuration of a liquid crystal device. Hereinafter, the configuration of the liquid crystal device will be described with reference to FIG. The liquid crystal device shown in FIG. 1 shows a case where the upper side in the drawing is the viewing side (observer side) and the lower side in the drawing is the light incident side.

  As shown in FIG. 1, the liquid crystal device 11 includes an element substrate 12, a counter substrate 13, and a liquid crystal layer 14 sandwiched between the element substrate 12 and the counter substrate 13.

  The element substrate 12 is formed on the first substrate 15 as a substrate made of a translucent material such as glass, the TFT element 16 formed on the liquid crystal layer 14 side of the first substrate 15, and the liquid crystal layer 14 side. The pixel electrode 17 and the first alignment film 18 are mainly configured.

  Specifically, a base protective film (buffer film) 21 made of a silicon oxide film or the like is formed on the first substrate 15 (the liquid crystal layer 14 side), and the base protective film 21 is made of polycrystalline silicon. A semiconductor film 22 is formed in a predetermined pattern. A gate insulating film 23 made of a silicon oxide film or the like is formed on the semiconductor film 22, and a gate electrode 24 is formed on the gate insulating film 23. The gate electrode 24 is made of, for example, an aluminum film.

  The side surface of the gate electrode 24 is tapered with respect to the surface of the gate insulating film 23, for example. Further, in the semiconductor film 22, a region facing the gate electrode 24 through the gate insulating film 23 is a channel region 25 in which a channel is formed by an electric field from the gate electrode 24.

  In the semiconductor film 22, a source region 26 is formed on one side (left side in the drawing) of the channel region 25, and a drain region 27 is formed on the other side (right side in the drawing). The pixel switching TFT element 16 is constituted by the gate electrode 24, the gate insulating film 23, the source electrode 28, the drain electrode 29, the source region 26 of the semiconductor film 22, the channel region 25, the drain region 27, and the like. The source electrode 28 and the drain electrode 29 are made of, for example, aluminum.

  The pixel switching TFT element 16 has an LDD structure. More specifically, in the source region 26, a source side high concentration region 26 having a relatively high impurity concentration and a source side low concentration region 31 (LDD region) having a relatively low impurity concentration are formed. In the drain region 27, a drain side high concentration region 27 having a relatively high impurity concentration and a drain side low concentration region 32 (LDD region) having a relatively low impurity concentration are formed.

  Further, a first interlayer insulating film 33 made of a silicon oxide film or the like is formed on the gate insulating film 23 on which the gate electrode 24 and the like are formed. On the first interlayer insulating film 33, the source electrode 28 and A drain electrode 29 is formed. The source electrode 28 is electrically connected to the source side high concentration region 26 of the semiconductor film 22. The drain electrode 29 is electrically connected to the drain side high concentration region 27 of the semiconductor film 22.

  A second interlayer insulating film 34 made of a silicon nitride film or the like is formed on the first interlayer insulating film 33 on which the source electrode 28 and the drain electrode 29 are formed. On the second interlayer insulating film 34, A pixel electrode 17 is formed. The pixel electrode 17 is made of a transparent conductive material such as indium tin oxide (ITO) and is electrically connected to the drain electrode 29 through a contact hole 35 formed in the second interlayer insulating film 34. Has been. A first alignment film 18 for controlling the alignment of liquid crystal molecules in the liquid crystal layer 14 is formed on the pixel electrode 17.

  In addition, the gate electrode 24 and the extended portion 36 (lower electrode) from the drain-side high concentration region 27 of the semiconductor film 22 are interposed via an insulating film (dielectric film) integrally formed with the gate insulating film 23. A capacitor line 37 formed in the same layer is disposed as an upper electrode so as to face each other, and a storage capacitor 38 is formed by the extended portion 36 and the capacitor line 37.

  On the other hand, the counter substrate 13 is mainly composed of a second substrate 41 made of a translucent material such as glass, a common electrode 42 formed on the surface of the liquid crystal layer 14, and a second alignment film 43. Yes.

  Specifically, light incident on the liquid crystal device 11 on the liquid crystal layer 14 side surface of the second substrate 41 is incident on at least the channel region 25 and the low concentration regions 31 and 32 of the semiconductor film 22. A light-shielding film 44 for preventing the above is formed. On the second substrate 41 on which the light shielding film 44 is formed, a common electrode 42 made of ITO or the like is formed over substantially the entire surface. A second alignment film 43 for controlling the alignment of the liquid crystal molecules in the liquid crystal layer 14 is formed on the common electrode 42 (the liquid crystal layer 14 side).

  2 and 3 are schematic views showing the manufacturing method of the MEMS device in the order of steps. Each drawing (a) is a schematic plan view of the MEMS device, and each drawing (b) is a schematic sectional view taken along a section AA ′ in each drawing (a). Hereinafter, a method for manufacturing a MEMS device will be described with reference to FIGS. The MEMS device 50 shown in FIGS. 2 and 3 is used as a sensor, and is formed, for example, in a partial region of the liquid crystal device 11 shown in FIG. As a manufacturing method of the MEMS device 50, a semiconductor manufacturing process and a MEMS manufacturing process are used.

As shown in FIG. 2, in the method of manufacturing the MEMS device 50, a film that functions as a weight (functional film) constituting a sensor is formed on the first substrate 15 (see FIG. 1). Specifically, first, a first silicon oxide film (SiO ₂ ) 51 is formed on the first substrate 15 by plasma CVD (Chemical Vapor Deposition), sputtering, or the like. The first silicon oxide film 51 may be formed together when forming the base protective film 21 and the gate insulating film 23 constituting the liquid crystal device 11.

  Next, a sacrificial layer 52 is formed on the first silicon oxide film 51. The sacrificial layer 52 includes, for example, a first sacrificial layer 52a made of aluminum or an aluminum-based alloy and a second sacrificial layer 52b made of ITO or the like. For example, the first sacrificial layer 52a is formed simultaneously with the formation of the gate electrode 24 made of an aluminum film. The thickness of the first sacrificial layer 52a is, for example, 100 nm. The first sacrificial layer 52a can be formed by sputtering, for example.

  Next, for example, simultaneously with the formation of the pixel electrode 17, the second sacrificial layer 52b is formed on the first sacrificial layer 52a by using a film formation technique. The thickness of the second sacrificial layer 52b is, for example, 100 nm. Next, the sacrificial layer 52 including the first sacrificial layer 52a and the second sacrificial layer 52b is patterned into a predetermined shape by using a photolithography technique and an etching technique.

  Next, a second silicon oxide film 53 made of a silicon oxide film is formed on the first silicon oxide film 51 and the sacrificial layer 52 by plasma CVD or sputtering. Thereafter, a silicon film (Si) 54 is formed on the second silicon oxide film 53 by plasma CVD or sputtering.

  Thereafter, a part of the silicon film 54 and the second silicon oxide film 53 is patterned in a comb shape by using a photolithography technique, an etching technique, and a MEMS technique, or the first cavity 55 and the second cavity The part 56 is formed.

  As described above, the structure in which the weight 58 made of the silicon film 54 and the second silicon oxide film 53 is supported by the beam 57 made of the silicon film 54 is completed.

  Next, as shown in FIG. 3, the sacrificial layer 52 is removed to form a cavity 61 below the weight 58. As a method for removing the sacrificial layer 52, an electrolytic corrosion reaction is used.

  The electrolytic corrosion reaction uses a potential difference between different metals and removes the metal in a self-control manner by bringing an etching solution into contact with the metal. The etchant is, for example, aqua regia. Aqua regia is a solution in which concentrated hydrochloric acid and concentrated nitric acid are mixed at a ratio of 1: 3. Specifically, the first sacrificial layer 52a and the second sacrificial layer 52b are eroded by the corrosion (oxidation) of the first sacrificial layer 52a and the dissolution (reduction) of the second sacrificial layer 52b using aqua regia as the electrolyte. To do.

  First, aqua regia is brought into contact with the sacrificial layer 52 (second sacrificial layer 52b). The second sacrificial layer 52b is gradually dissolved by aqua regia, and when the aqua regia comes into contact with the first sacrificial layer 52a, the first sacrificial layer 52a and the second sacrificial layer 52b are removed by an electrolytic corrosion reaction ( Eroded). Alternatively, a portion where the first sacrificial layer 52a is not covered with the second sacrificial layer 52b is formed in advance, and the first sacrificial layer 52a and the second sacrificial layer 52b are brought into contact with aqua regia, thereby causing an erosion reaction. Thus, the first sacrificial layer 52a and the second sacrificial layer 52b are removed (eroded). More specifically, the potential difference between the oxidation potential of the first sacrificial layer 52a and the reduction potential of the second sacrificial layer 52b in aqua regia serves as a driving force for the reaction, and the oxidation and second of the first sacrificial layer 52a are performed. Reduction of the sacrificial layer 52b is promoted.

  As described above, the sacrificial layer 52 (the first sacrificial layer 52a and the second sacrificial layer 52b) is removed by using the electrolytic corrosion reaction, and then the weight 58 and the first silicon oxide film are removed after the sacrificial layer 52 is removed. It is possible to suppress the occurrence of a sticking phenomenon or the like due to the etching solution remaining between the first and second layers. Further, even the sacrificial layer 52 having a slight thickness can be removed by the electrolytic corrosion reaction. As a result, the cavity 61 can be formed below the weight 58, and the MEMS device 50 can function as a sensor.

  As a result, the sacrificial layer 52 is removed, and the stacked body composed of the second silicon oxide film 53 and the silicon film 54 that functions as the weight 58 constituting the MEMS device (sensor) is in a floating state. As shown in FIG. 3A, the shape of the weight 58 is preferably a square in plan view, for example, since the sensitivity in the front-rear and left-right directions is observed. Moreover, since the above sensors are built in the liquid crystal device 11, for example, a plurality of sensors can be built.

  Next, an acceleration sensor that is one of the above-described sensors will be described. The acceleration sensor is configured to support the weight 58 with the beam 57 as described above, for example. The beam 57 is formed in, for example, a comb shape. A fixed electrode 59 is provided adjacent to the comb-shaped beam 57. The acceleration sensor detects, for example, a capacitance type, and measures the displacement with the capacitance between the beam 57 and the fixed electrode 59. Moreover, it is not limited to an acceleration sensor, It can also apply to various sensors, such as a gyro sensor.

  By incorporating such a MEMS device 50 in the liquid crystal device 11, for example, when a mobile phone equipped with the liquid crystal device 11 is dropped, the sensor detects the fall, thereby protecting the memory from being damaged. It can be applied to such usage. In addition, for example, the present invention can be applied to a method in which the orientation of a mobile phone is detected by a sensor and the display orientation is changed according to the orientation.

  As described above in detail, according to the method for manufacturing the MEMS device 50 of the present embodiment, the following effects can be obtained.

  (1) According to this embodiment, the sacrificial layer 52 can be removed (eroded) in a self-controlling manner by using the electrolytic corrosion reaction, and thus the cavity after the sacrificial layer 52 is removed. It becomes possible to suppress aqua regia sticking to 61 part. Therefore, it is possible to prevent the weight 58 laminated with the second silicon oxide film 53 and the silicon film 54 from being attracted by aqua regia and the first silicon oxide film 51 and the weight 58 to be in close contact (sticking). As a result, the bottom of the weight 58 can be hollowed out, and the laminated film can function as a movable weight 58. Further, since the electrolytic corrosion reaction is used, the sacrificial layer 52 having a slight thickness can be removed, and the etching processing time can be shortened.

  (2) According to the present embodiment, the sacrificial layer 52 (the first sacrificial layer 52a made of an aluminum film and the second sacrificial layer 52b made of ITO) is made of the material used for the liquid crystal device 11, and other materials are newly added. In addition, it is possible to form the sacrificial layer 52 together with the process of the manufacturing method of the liquid crystal device 11, and the MEMS device 50 can be formed efficiently.

  In addition, embodiment is not limited above, It can also implement with the following forms.

(Modification 1)
As described above, instead of forming the sacrificial layer 52 (52a, 52b) on the relatively planarized first silicon oxide film 51, for example, as shown in FIGS. 4 and 5, dimple processing is performed. It is preferable to form the sacrificial layer 52 on the unevenness 62 as described above. FIG. 4 is a schematic cross-sectional view showing the structure of the MEMS device 50 before the sacrificial layer 52 is removed. FIG. 5 is a schematic cross-sectional view showing the structure of the MEMS device 50 after the sacrificial layer 52 is removed. As a method of making the portion of the first silicon oxide film 51 in contact with the sacrificial layer 52 into the uneven shape 62, for example, a photolithography technique and an etching technique may be used. The shape of the unevenness 62 may be irregularly roughened. The first sacrificial layer 52a is formed in an uneven shape reflecting the uneven shape of the first silicon oxide film 51. The irregular shape may be a round shape or a wave shape. According to this, the force of the surface tension is not easily transmitted to the aqua regia, and the aqua regia can be easily separated. As a result, the etching property of the sacrificial layer 52 is improved, and sticking can be further suppressed.

(Modification 2)
As described above, the sacrificial layer 52 is not limited to the combination of the aluminum film that is the first sacrificial layer 52a and the ITO that is the second sacrificial layer 52b. For example, the sacrificial layer 52 is not limited to the material used for the display. Such a combination of materials may be used. For example, one metal material is composed of gold (Au) or platinum (Pt), and the other metal is composed of nichrome (NiCr), nickel (Ni), tungsten (W), or tantalum (Ta). It may be used.

(Modification 3)
As described above, the first sacrificial layer 52 a is not limited to be formed together with the gate electrode 24, and may be formed together with the source electrode 28 or the drain electrode 29, for example. In addition to the above, it may be formed together with a reflective electrode (not shown). In this case, for example, a reflective electrode is formed between the second interlayer insulating film 34 and the pixel electrode 17.

(Modification 4)
As described above, the sacrificial layer 52 is not limited to the two-layer structure of the first sacrificial layer 52a and the second sacrificial layer 52b. For example, a multi-layer structure such as a three-layer structure may be used. .

(Modification 5)
As described above, it is not limited to forming the first sacrificial layer 52a, the second sacrificial layer 52b, and the first silicon oxide film 51 together with manufacturing the liquid crystal device 11, but the second silicon oxide film 53 and the silicon The film 54 may also be formed together.

(Modification 6)
As described above, the material formed around the sacrificial layer 52 is not limited to the silicon oxide film (51, 53) or the silicon film (54). For example, the following materials are used. It may be. In the case of using a silicon wafer or SOI (Silicon On Insulator), silicon may be used instead of the silicon oxide film. If a display material is used, a photosensitive acrylic resin may be used instead of the first silicon oxide film. In place of the silicon film, a silicon oxide film, a silicon nitride film (SiN), titanium (Ti), titanium nitride (TiN), molybdenum (Mo), or tungsten (W) may be used.

(Modification 7)
As described above, the MEMS device 50 is not limited to being built in the liquid crystal device 11 and may be built in an electro-optical device such as an organic EL device.

FIG. 2 is a schematic cross-sectional view illustrating a configuration of a liquid crystal device according to the present embodiment. It is a schematic diagram which shows the manufacturing method of a MEMS device in order of a process, (a) is a schematic plan view, (b) is a schematic cross section. It is a schematic diagram which shows the manufacturing method of a MEMS device in order of a process, (a) is a schematic plan view, (b) is a schematic cross section. The schematic cross section which shows the modification of the manufacturing method of a MEMS device. The schematic cross section which shows the modification of the manufacturing method of a MEMS device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Liquid crystal device, 12 ... Element board | substrate, 13 ... Opposite board | substrate, 14 ... Liquid crystal layer, 15 ... 1st board | substrate as a board | substrate, 16 ... TFT element, 17 ... Pixel electrode, 18 ... 1st alignment film, 21 ... Base protection Film, 22 ... semiconductor film, 23 ... gate insulating film, 24 ... gate electrode, 25 ... channel region, 26 ... source region, 27 ... drain region, 28 ... source electrode, 29 ... drain electrode, 31 ... source side low concentration region 32 ... Drain-side low concentration region, 33 ... first interlayer insulating film, 34 ... second interlayer insulating film, 35 ... contact hole, 36 ... extended portion, 37 ... capacitor line, 38 ... storage capacitor, 41 ... second Substrate, 42 ... common electrode, 43 ... second alignment film, 44 ... light shielding film, 50 ... MEMS device, 51 ... first silicon oxide film, 52 ... sacrificial layer, 52a ... first sacrificial layer, 52b ... second sacrificial layer 53 ... Secondary silicon acid Film, 54 ... silicon film, 55 ... first cavity, 56 ... second cavity, 57 ... beam 58 ... weight of the functional film, 61 ... cavity, 62 ... uneven.

Claims (9)

Forming a sacrificial layer that causes an electrolytic corrosion reaction on the substrate;
Forming a functional film on the sacrificial layer;
Removing the sacrificial layer using the electrolytic corrosion reaction to form a cavity under the functional film;
A method for manufacturing a MEMS device, comprising: A method of manufacturing a MEMS device according to claim 1,
The method of manufacturing a MEMS device, wherein the functional film is movably supported. A method for manufacturing a MEMS device according to claim 1 or 2,
The method for manufacturing a MEMS device, wherein the sacrificial layer includes aluminum or an aluminum-based alloy and an ITO alloy. A method for manufacturing a MEMS device according to claim 3,
The said aluminum or aluminum-type alloy is formed simultaneously with a gate electrode, The manufacturing method of the MEMS device characterized by the above-mentioned. A method for manufacturing a MEMS device according to claim 3,
The method of manufacturing a MEMS device, wherein the aluminum or aluminum-based alloy is formed simultaneously with a source electrode or a drain electrode. A method for manufacturing a MEMS device according to claim 3,
The said aluminum or aluminum-type alloy is formed simultaneously with a reflective electrode, The manufacturing method of the MEMS device characterized by the above-mentioned. A method for manufacturing a MEMS device according to any one of claims 3 to 6, comprising:
The method of manufacturing a MEMS device, wherein the ITO alloy is formed simultaneously with a pixel electrode. A method for manufacturing a MEMS device according to any one of claims 1 to 7,
The functional film functions as a weight supported by a beam, and is used as a part of a sensor. A method for manufacturing a MEMS device according to any one of claims 1 to 8,
Prior to the step of forming the sacrificial layer, the surface of the substrate or the film formed on the substrate in contact with the sacrificial layer is roughened.

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