JP2015145038A - Mems element and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a MEMS element which suppresses the generation of gas from an inner wall in a space in which a MEMS part is positioned, and allows an electrode of the MEMS part to be drawn out of the space.SOLUTION: A MEMS part 15 having first and second electrodes 15a, 15b is arranged in a space 61 covered by a first silicon nitride film 14 and a silicon film 18. The silicon film includes first and second ring-shaped holes 18a, 18b. The silicon film positioned inside the first ring-shaped hole is electrically connected to the first electrode. The silicon film positioned inside the second ring-shaped hole is electrically connected to the second electrode. The first and second ring-shaped holes are each filled with a second silicon nitride film 36.

Description

  The present invention relates to a micro electro mechanical systems (MEMS) element and a manufacturing method thereof.

  A conventional MEMS element is manufactured by arranging a MEMS portion such as a vibrator in a space such as a cavity sealed with a vacuum seal or an inert gas having a constant pressure (see, for example, Patent Document 1). The space such as the cavity is formed by using an insulating film made of a silicon oxide film as a sacrificial material and removing the sacrificial material by etching. For this reason, a silicon oxide film that easily generates gas is often used on the inner wall of a space such as a cavity. As a result, gas generated from the silicon oxide film accumulates in the space, which may deteriorate the degree of vacuum or change the hermetic sealing pressure. As a result, the performance and reliability of the MEMS unit are reduced.

JP2010-30021 (FIG. 4)

  Some embodiments of the present invention relate to a MEMS element that can take out an electrode of a MEMS part to the outside of the space while suppressing generation of gas from an inner wall of the space in which the MEMS part is disposed, and a method of manufacturing the MEMS element. doing.

  In one embodiment of the present invention, a MEMS portion including first and second electrodes is disposed in a space covered with a first silicon nitride film and a silicon film, and the silicon film includes the first and second electrodes. The silicon film which has a ring-shaped hole and is located inside the first ring-shaped hole is electrically connected to the first electrode, and is formed inside the second ring-shaped hole. The MEMS film, wherein the silicon film located is electrically connected to the second electrode, and each of the first and second ring-shaped holes is filled with a second silicon nitride film. It is an element.

  According to the one aspect of the present invention, since the space for arranging the MEMS portion is formed by the silicon nitride film and the silicon film, generation of gas from the inner wall of the space can be suppressed, and the first ring-shaped hole By electrically connecting the silicon film located inside to the first electrode and electrically connecting the silicon film located inside the second ring-shaped hole to the second electrode, the MEMS portion Can be taken out of the space.

  In the aspect of the present invention described above, the MEMS unit is disposed on the first silicon nitride film, and the silicon film is disposed above the MEMS unit and is located around the MEMS unit. 1 is in close contact with the silicon nitride film.

  According to the above aspect of the present invention, the silicon film is adhered to the first silicon nitride film located around the MEMS portion, so that the silicon film covering the upper portion of the MEMS portion and the first nitride under the MEMS portion are provided. The silicon film can be three-dimensionally surrounded and sealed to form an airtight structure.

  In the above aspect of the present invention, the first electrode base disposed on the first electrode and disposed below the silicon film located inside the first ring-shaped hole, A second electrode base disposed on the second electrode and disposed under the silicon film located inside the second ring-shaped hole; and a silicon base closely adhered on the first silicon nitride film The MEMS part is disposed on the first silicon nitride film, the silicon stage is located around the MEMS part, the silicon film is disposed above the MEMS part, and It is in close contact with the silicon base.

  According to the one aspect of the present invention, since the space for arranging the MEMS portion is formed by the silicon nitride film and the silicon film, generation of gas from the inner wall of the space can be suppressed, and the first ring-shaped hole can be formed. The silicon film located inside is electrically connected to the first electrode via the first electrode base, and the silicon film located inside the second ring-shaped hole is connected via the second electrode base. By electrically connecting to the second electrode, the electrode of the MEMS portion can be taken out of the space.

  In the above embodiment of the present invention, the silicon film has a first hole, and the first hole is filled with a metal film. The metal film, the silicon film, the first and second holes An airtight structure is formed by the silicon nitride film.

  In one embodiment of the present invention, a first insulating film formed on the silicon film, a second hole formed on the first insulating film and positioned on the first hole, A second insulating film formed on the first insulating film, and the first and second holes are filled with the metal film.

  According to one embodiment of the present invention, the first and second holes are filled with the metal film, and the second insulating film is formed over the metal film, whereby the metal film is completely filled. For this reason, the metal film is not exposed on the second insulating film. Therefore, it is possible to improve the resistance of the MEMS portion against external mechanical stress.

  In one embodiment of the present invention, the first hole is not disposed immediately above the movable electrode of the MEMS portion. Thereby, it can suppress that the reliability of a MEMS part falls.

  In one embodiment of the present invention, the MEMS portion is disposed on a semiconductor substrate, and an integrated circuit is formed on the semiconductor substrate. By forming the MEMS portion together with the integrated circuit on the semiconductor substrate as described above, it is possible to reduce the size or the manufacturing cost.

  According to one embodiment of the present invention, a MEMS portion having first and second electrodes is formed over a first silicon nitride film, a sacrificial layer covering the MEMS portion is formed over the first silicon nitride film, A first connection hole located on the first electrode and a second connection hole located on the second electrode are formed in the sacrificial layer, and the first connection hole located around the sacrifice layer is formed. A silicon film is formed on the silicon nitride film and covers the sacrificial layer in the first and second connection holes, and a first ring-shaped hole is formed in the silicon film. The silicon film in the first connection hole is separated, and the silicon film in the second connection hole is separated by forming a second ring-shaped hole in the silicon film. 2 ring-shaped holes are filled with the second silicon nitride film The first and second silicon nitride films are formed by forming a first hole in the silicon film and removing the sacrificial layer by supplying a wet etching solution to the sacrificial layer through the first hole. And a MEMS part is located in a space covered with the silicon film.

  According to the one aspect of the present invention, since the space in which the MEMS portion is disposed is surrounded by the silicon nitride film and the silicon film, generation of gas from the inner wall of the space can be suppressed, and the inside of the first ring-shaped hole By electrically connecting the silicon film located at the first electrode to the first electrode and electrically connecting the silicon film located inside the second ring-shaped hole to the second electrode, The electrode can be taken out of the space.

  According to one embodiment of the present invention, a MEMS portion having first and second electrodes is formed over a first silicon nitride film, a sacrificial layer covering the MEMS portion is formed over the first silicon nitride film, A first connection hole located on the first electrode and a second connection hole located on the second electrode are formed in the sacrificial layer, and the first connection hole located around the sacrifice layer is formed. A silicon film is formed on the silicon nitride film and covers the sacrificial layer in the first and second connection holes, and a first ring-shaped hole is formed in the silicon film. The silicon film in the first connection hole is separated, and the silicon film in the second connection hole is separated by forming a second ring-shaped hole in the silicon film, and the first Forming a hole, the first hole, the first and second ring-shaped Is buried by a second silicon nitride film, the second silicon nitride film buried in the first hole is removed, and a wet etching solution is supplied to the sacrificial layer through the first hole. By removing the layer, the MEMS part is located in a space covered with the first and second silicon nitride films and the silicon film.

  According to the one aspect of the present invention, since the space in which the MEMS portion is disposed is surrounded by the silicon nitride film and the silicon film, generation of gas from the inner wall of the space can be suppressed, and the inside of the first ring-shaped hole By electrically connecting the silicon film located at the first electrode to the first electrode and electrically connecting the silicon film located inside the second ring-shaped hole to the second electrode, The electrode can be taken out of the space.

  In one embodiment of the present invention, the MEMS unit includes a movable electrode. When the MEMS unit is formed, the first and second electrodes and the first and second electrodes are formed over the first silicon nitride film. After forming the first silicon stand surrounding the second electrode, the first electrode stand is formed on the first electrode and the movable electrode and the second electrode stand are formed on the second electrode. At the same time, when the second silicon base is formed on the first silicon base and the sacrificial layer covering the MEMS portion is formed, the first and second electrode bases and the first and second silicon bases are formed. The sacrificial layer covering the base is formed on the first silicon nitride film, and when the first and second connection holes are formed in the sacrificial layer, the sacrificial layer is formed on the first electrode base. The first connection hole located on the second electrode base and the second contact located on the second electrode base When forming a hole and a groove located on the second silicon stage, and forming the silicon film, the silicon film is formed in the groove, and the sacrificial layer is removed, so that the MEMS is formed in the space. Part, first and second electrode bases, and first and second silicon bases.

  According to the one aspect of the present invention, since the space in which the MEMS portion is disposed is surrounded by the silicon nitride film and the silicon film, generation of gas from the inner wall of the space can be suppressed, and the inside of the first ring-shaped hole The silicon film located at the first electrode table is electrically connected to the first electrode via the first electrode table, and the silicon film located inside the second ring-shaped hole is connected via the second electrode table. By electrically connecting to the second electrode, the electrode of the MEMS portion can be taken out of the space.

  In the embodiment of the present invention, after the sacrificial layer is removed, the space is sealed by embedding a metal film in the first hole by sputtering.

(A) is a top view which shows the MEMS element which concerns on 1 aspect of this invention, (B) is sectional drawing along the AA 'line shown to (A). (A)-(E) are sectional drawings for demonstrating the manufacturing method of the MEMS element shown to FIG. 1 (B). (A), (B) is sectional drawing for demonstrating the manufacturing method of the MEMS element shown to FIG. 1 (B). Sectional drawing for demonstrating the manufacturing method of the MEMS element shown to FIG. 1 (B). (A) is a top view which shows the MEMS element which concerns on a comparative example, (B) is sectional drawing along the BB 'line shown in (A), and sectional drawing along the CC' line. (A)-(G) are sectional drawings for demonstrating the manufacturing method of the MEMS element shown to FIG. 5 (B). Sectional drawing for demonstrating the manufacturing method of the MEMS element shown to FIG. 5 (B). (A) is a top view which shows the MEMS element which concerns on 1 aspect of this invention, (B) is sectional drawing along the AA 'line shown to (A).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments below.

[Embodiment 1]
1A is a plan view illustrating a MEMS element according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA ′ illustrated in FIG. 2 to 4 are cross-sectional views for explaining a method of manufacturing the MEMS element shown in FIG.

  According to one embodiment of the present invention, a manufacturing process of a MEMS element with an airtight structure is inserted with good affinity immediately before formation of a field effect transistor (FET) in the middle of a manufacturing process of a semiconductor integrated circuit serving as a base, followed by FET formation. After the steps such as forming the wiring layer and the like, the airtight structure of the cavity is produced.

  First, as shown in FIG. 2A, an element isolation film (STI: Shallow Trench Isolation) 12 is formed in the element isolation region of the silicon substrate 11. Next, an oxide film 13 is formed in the active region of the silicon substrate 11. Next, a first silicon nitride film 14 is formed on the entire surface including the element isolation film 12.

Next, the MEMS portion 15 is formed on the first silicon nitride film 14. This will be described in detail below.
A first conductive film is formed on the first silicon nitride film 14, and the first conductive film is patterned, whereby the first electrode 15a and the second electrode 15b made of the first conductive film are changed to the first conductive film. 1 on the silicon nitride film 14. Note that the first conductive film is, for example, any one of a polycrystalline silicon film, an amorphous silicon film, and a single crystal silicon film. Next, a gap insulating film 16 is formed on the first silicon nitride film 14 and the first and second electrodes 15a and 15b, and the gap insulating film 16 is patterned. Next, a second conductive film is formed on the entire surface including the gap insulating film 16, and the second conductive film is patterned, so that the movable electrode 15c made of the second conductive film is formed on the gap insulating film 16. To form. Note that the second conductive film is, for example, one of a polycrystalline silicon film, an amorphous silicon film, and a single crystal silicon film. The movable electrode 15c is electrically connected to the first electrode 15a. In this manner, the MEMS portion 15 having the first electrode 15a, the second electrode 15b, and the movable electrode 15c is formed on the first silicon nitride film 14 (see FIG. 1A).

  In the present specification, the “MEMS portion” is meant to include various elements as long as it has a movable electrode and at least two electrodes, such as a resonator.

  Thereafter, as shown in FIG. 2B, the gap insulating film 16 is removed by etching. Note that the gap insulating film 16 may be removed together with the sacrificial layer 17 in a later step of removing the sacrificial layer 17. Next, heat treatment is performed on the MEMS unit 15 in a nitrogen atmosphere. Thereby, the stress of the MEMS part 15 can be released.

  Next, as shown in FIG. 2C, a sacrificial layer 17 that covers the MEMS portion 15 is formed on the first silicon nitride film 14. The sacrificial layer 17 serves to protect the MEMS portion 15.

  Thereafter, as shown in FIG. 2D, by patterning the sacrificial layer 17, the first connection hole 21 and the second connection hole 22 are formed in the sacrificial layer 17, and unnecessary sacrificial layers are removed. . Next, the first silicon nitride film 14 is patterned.

  Next, as illustrated in FIG. 2E, the integrated circuit portion 30 is formed on the silicon substrate 11. This will be described in detail below.

  A well (not shown) is formed by implanting impurity ions into the silicon substrate 11, and the oxide film 13 in the active region is removed. Next, a gate insulating film 31 is formed in the active region of the silicon substrate 11 by a thermal oxidation method. Next, the surfaces of the first and second electrodes 15a and 15b exposed in the first and second connection holes 21 and 22 are etched. Thereby, the electrical contact of the first and second electrodes 15a and 15b by the first and second connection holes 21 and 22 is prevented from being hindered.

  It should be noted that other methods may be used as a method for preventing the electrical contact between the first and second electrodes 15a and 15b from being hindered, for example, before the first silicon nitride film 14 is patterned. This can also be realized by forming a polysilicon film as the silicon film 18 that is in close contact with the first silicon nitride film 14 positioned around the layer 17 and covers the sacrificial layer 17. However, in this method, the polysilicon film that is the silicon film 18 covering the sacrificial layer 17 and the polysilicon film that is the gate electrode 32 of the integrated circuit section 30 are formed in separate steps. Thus, the method of forming in separate steps has an advantage that a polysilicon film suitable for the silicon film 18 covering the sacrificial layer 17 can be adopted, and a polysilicon film suitable for the gate electrode 32 can be adopted. However, in the present embodiment, a method of forming the silicon film 18 and the gate electrode 32 with the same polysilicon film will be described. This method has the advantage that the process can be shortened.

  Next, a polysilicon film is formed so as to cover the gate insulating film 31 and the sacrificial layer 17, and this polysilicon film is patterned. As a result, a gate electrode 32 is formed on the gate insulating film 31, a silicon film 18 that is in close contact with the first silicon nitride film 14 located around the sacrificial layer 17 and covers the sacrificial layer 17 is formed. A silicon film 18 (hereinafter also referred to as an “electrode post”) is formed in the first and second connection holes 21 and 22, and first and second ring-shaped holes 18 a and 18 b are formed in the silicon film 18. The At this time, the electrode post 18 in the first connection hole 21 is electrically separated from the other silicon film 18 by the first and second ring-shaped holes 18 a and 18 b, and the second connection hole 22. The inner electrode post 18 is electrically isolated from the other silicon film 18. The electrode post 18 in the first connection hole 21 is electrically connected to the first electrode 15a, and the electrode post 18 in the second connection hole 22 is electrically connected to the second electrode 15b. . That is, the silicon film 18 positioned inside each of the first and second ring-shaped holes 18a and 18b is electrically connected to the first and second electrodes 15a and 15b of the MEMS portion 15 (FIG. 2 ( E), see FIG.

  In this specification, the “ring-shaped hole” is a hole having a function of electrically separating in addition to the rectangular hole having a circular planar shape as shown in FIG. For example, it includes holes having various shapes (for example, circular or elliptical).

  Next, a low concentration impurity layer (not shown) is formed in a self-aligning manner using the gate electrode 32 as a mask. Next, a sidewall 33 made of a silicon nitride film is formed on the sidewall of the gate electrode 32. The sidewall 33 is also formed on the sidewall of the silicon film 18. Next, the source diffusion layer 34 and the drain diffusion layer 35 are formed in a self-aligning manner using the gate electrode 32 and the sidewall 33 as a mask. Although a silicon oxide film can be used for the sidewall 33 of the gate electrode 32, in this case, the sidewall made of the silicon oxide film formed on the sidewall of the silicon film 18 is removed.

  Next, as shown in FIG. 3A, a second silicon nitride film 36 is formed on the entire surface including the insides of the first and second ring-shaped holes 18a and 18b. As a result, the first and second ring-shaped holes 18 a and 18 b are filled with the second silicon nitride film 36. The second silicon nitride film 36 is in close contact with the silicon film 18 on the side walls of the first and second ring-shaped holes 18a and 18b, so that the first and second ring-shaped holes 18a and 18b are completely formed. The airtight structure after removal of the sacrificial layer can be realized in a later process.

  Next, a first interlayer insulating film 37 made of a silicon oxide film is formed on the second silicon nitride film 36. Next, a photoresist film (not shown) is formed on the first interlayer insulating film 37, and the first interlayer insulating film 37 and the second silicon nitride film 36 are etched using the photoresist film as a mask. Thus, second holes 23 and 24 located on the silicon film 18 are formed in the first interlayer insulating film and the second silicon nitride film 36. Next, the sacrifice layer 17 is exposed by forming release holes (first holes) 25 and 26 below the second holes 23 and 24 in the silicon film 18.

  In the present embodiment, the release holes 25 and 26 are formed after the second holes 23 and 24 are formed, but the following modifications may be made. When the first and second ring-shaped holes 18a and 18b are formed in the silicon film 18 in the process shown in FIG. 2E, the release holes 25 and the first and second ring-shaped holes 18a and 18b are formed. 26 is formed in the silicon film 18, and when the second silicon nitride film 36 is embedded in the first and second ring-shaped holes 18a and 18b in the step shown in FIG. The second silicon nitride film 36 is embedded in the ring-shaped holes 18a and 18b and the release holes 25 and 26, and then a first interlayer insulating film 37 is formed on the second silicon nitride film 36. The second holes 23 and 24 are formed in the first interlayer insulating film 37 and the second silicon nitride film 36, whereby the first holes in the release holes 25 and 26 located under the second holes 23 and 24, respectively. 2 by removing the silicon nitride film 36牲層 17 may be exposed.

  Thereafter, a wet etching solution is supplied to the sacrificial layer 17 through the second holes 23 and 24 and the release holes 25 and 26. Thereby, the sacrificial layer 17 is removed as shown in FIG. A space 61 is formed in the portion where the sacrificial layer 17 is removed. The space 61 is a space covered with the silicon nitride film and the silicon film 18, and the MEMS unit 15 is located in the space 61. Note that since the silicon film 18 and the silicon nitride film have good adhesion, no seepage of the wet etching solution occurs.

  Next, a metal film 71 (for example, an Al alloy film) is formed by sputtering in the second holes 23 and 24, in the release holes 25 and 26, and on the first interlayer insulating film 37. As a result, the metal film 71 is embedded in the second holes 23 and 24 and the release holes 25 and 26. As a result, the MEMS portion 15 is surrounded by the metal film 71, the first and second silicon nitride films 14 and 36, and the silicon film 18, and an airtight structure is formed (see FIG. 3B). The degree of vacuum (pressure) of the space 61 is the same as the degree of vacuum (pressure) when the metal film 71 is sputtered.

  When the metal film 71 is sputtered, a part of the metal film 71 may enter the space 61 below the release holes 25 and 26. Therefore, it is preferable that the release holes 25 and 26 are not arranged immediately above the movable electrode 15c of the MEMS unit 15. This is because if the metal film 71 enters the movable electrode 15c, the performance of the MEMS unit 15 may be deteriorated.

  In addition, in this specification, “airtight structure” means a structure that can be sealed by sealing a gas at a constant pressure in addition to a structure that can be sealed in a high vacuum state. It is meant to include structures that are not in a state.

  Next, as shown in FIG. 4, after the metal film 71 on the first interlayer insulating film 37 is removed by etching back, the first interlayer insulating film 37 is planarized by CMP (Chemical Mechanical Polishing).

Next, third to sixth connection holes 41a, 42a, 43a, and 44a are formed in the first interlayer insulating film 37 and the second silicon nitride film 36 by etching. The third and fourth connection holes 41a and 42a are provided on electrode posts that are part of the silicon film 18 surrounded by the first and second ring-shaped holes 18a and 18b and insulated from the surroundings. It has been. The fifth and sixth connection holes 43a and 44a are drawn as typical examples of normal contacts of the integrated circuit part provided outside the MEMS part region. After this connection hole forming step, except for the sacrificial layer release etching, it is almost the same as the wiring process of a normal integrated circuit. Note that the presence of the integrated circuit area is not essential.
Next, a third conductive film is formed in the third to sixth connection holes 41 a, 42 a, 43 a, 44 a and on the first interlayer insulating film 37, and the third conductive film existing on the first interlayer insulating film 37 is formed. 3 is removed by CMP or etchback. Thus, the first conductive plug 41 is embedded in the third connection hole 41a, the second conductive plug 42 is embedded in the fourth connection hole 42a, and the fifth connection hole 43a is embedded. The third conductive plug 43 is embedded, and the fourth conductive plug 44 is embedded in the sixth connection hole 44a. As a result, the first conductive plug 41 is electrically connected to the silicon film (electrode post) 18 located in the first connection hole 21, and the second conductive plug 42 is located in the second connection hole 22. The third conductive plug 43 is electrically connected to the source diffusion layer 34, and the fourth conductive plug 44 is electrically connected to the drain diffusion layer 35. The

  Next, a conductive film is formed on the first interlayer insulating film 37 and the first to fourth conductive plugs 41, 42, 43, and 44, and this conductive film is patterned. As a result, the first wiring layers 51, 52, 53, and 54 are formed on the first to fourth conductive plugs 41, 42, 43, and 44, respectively, and the metal buried in the second hole is formed. Cap layers 157 and 158 are formed on the film 71. In the present specification, the “wiring layer” means a plurality of wirings formed in a certain layer.

  Thereafter, as shown in FIG. 1B, a second interlayer insulating film 38 made of a silicon oxide film is formed on the first interlayer insulating film 37, the first wiring layers 51 and 52, and the cap layers 157 and 158. A second interlayer insulating film 38 is planarized by CMP.

  Next, seventh and eighth connection holes 45a, 46a and ninth and tenth connection holes (not shown) are formed in the second interlayer insulating film 38 by etching. Next, a fourth conductive film is formed in the seventh to tenth connection holes 45 a and 46 a and on the second interlayer insulating film 38, and the fourth conductive film existing on the second interlayer insulating film 38 is formed. Are removed by CMP or etchback. As a result, the fifth conductive plug 45 is embedded in the seventh connection hole 45a, the sixth conductive plug 46 is embedded in the eighth connection hole 46a, and the ninth connection hole (not shown). ) Is embedded in a seventh conductive plug (not shown), and an eighth conductive plug (not shown) is embedded in a tenth connection hole (not shown). As a result, the fifth and sixth conductive plugs 45 and 46 are electrically connected to the first wiring layers 51 and 52, respectively, and the seventh and eighth conductive plugs are connected to the first wiring layers 53 and 54, respectively. Electrically connected.

  Next, second wiring layers 55 and 56 are formed on the second interlayer insulating film 38 and the fifth and sixth conductive plugs 45 and 46, and the second interlayer insulating film 38 and the seventh and eighth conductive layers are formed. A second wiring layer (not shown) is formed on the plug. Next, a protective film (third insulating film) 39 is formed on the second interlayer insulating film 38 and the second wiring layers 55 and 56.

<Comparative example>
In order to clarify the effect of this embodiment, a comparative example will be described.
FIG. 5A is a plan view showing a MEMS element according to a comparative example, and FIG. 5B is a cross-sectional view along the line BB ′ shown in FIG. 5A and the line CC ′. FIG. 6 and 7 are cross-sectional views for explaining a method of manufacturing the MEMS element shown in FIG.

  First, in the step shown in FIG. 6A, a first conductive film is formed on the first silicon nitride film 14, and the first conductive film is patterned to form a first conductive film made of the first conductive film. The process is the same as that shown in FIG. 2A except that a base 15d is formed in addition to the first and second electrodes 15a and 15b.

  6B is the same as the process shown in FIG. 2B, and the process shown in FIG. 6C is the same as the process shown in FIG.

  Thereafter, as shown in FIG. 6D, the sacrificial layer 17 is patterned, and the first silicon nitride film 14 is patterned.

  Next, in the step shown in FIG. 6E, the integrated circuit portion 30 is formed on the silicon substrate 11 as in the step shown in FIG. This will be described in detail below.

  A well (not shown) is formed by implanting impurity ions into the silicon substrate 11, and the oxide film 13 in the active region is removed. Next, a gate insulating film 31 is formed in the active region of the silicon substrate 11 by a thermal oxidation method. Next, a polysilicon film is formed on the gate insulating film 31, and this polysilicon film is patterned to form a gate electrode 32 on the gate insulating film 31.

  Next, a low concentration impurity layer (not shown) is formed in a self-aligning manner using the gate electrode 32 as a mask. Next, a sidewall 33 made of a silicon nitride film is formed on the sidewall of the gate electrode 32. Next, the source diffusion layer 34 and the drain diffusion layer 35 are formed in a self-aligning manner using the gate electrode 32 and the sidewall 33 as a mask.

  Next, as shown in FIG. 6F, a first interlayer insulating film 37 made of a silicon oxide film is formed on the entire surface including the sacrificial layer 17.

  Thereafter, as shown in FIG. 6G, the first interlayer insulating film 37 is planarized by CMP.

  Next, as shown in FIG. 7, a groove 81a and fifth and sixth connection holes 43a and 44a covering the periphery of the MEMS portion 15 are formed in the first interlayer insulating film 37 and the sacrificial layer 17 by etching. Next, a third conductive film is formed in the trench 81 a, in the fifth and sixth connection holes 43 a and 44 a, and on the first interlayer insulating film 37, and the first conductive film present on the first interlayer insulating film 37 is formed. 3 is removed by CMP or etchback. Thereby, the wall-shaped conductive stack 81 is embedded in the groove 81a, the third conductive plug 43 is embedded in the fifth connection hole 43a, and the fourth conductive hole is embedded in the sixth connection hole 44a. Plug 44 is embedded. As a result, the conductive stack 81 is connected to the base 15d, the third conductive plug 43 is electrically connected to the source diffusion layer 34, and the fourth conductive plug 44 is electrically connected to the drain diffusion layer 35.

  Next, a wall-like wiring stack 82 and first wiring layers 53 and 54 are formed on the first interlayer insulating film 37, the conductive stack 81, and the third and fourth conductive plugs 43 and 44.

  Next, a second interlayer insulating film 38 made of a silicon oxide film is formed on the first interlayer insulating film 37, the wiring stack 82, and the first wiring layers 53 and 54, and the second interlayer insulating film 38 is CMP. To flatten.

  Next, a groove 83a and ninth and tenth connection holes 47a and 48a are formed in the second interlayer insulating film 38 by etching. Next, a fourth conductive film is formed in the trench 83 a, the ninth and tenth connection holes 47 a and 48 a, and the second interlayer insulating film 38, and the fourth conductive film present on the second interlayer insulating film 38 is formed. The conductive film 4 is removed by CMP or etchback. As a result, the wall-like conductive stack 83 is embedded in the groove 83a, the seventh conductive plug 47 is embedded in the ninth connection hole 47a, and the eighth conductive hole 48a is embedded in the tenth connection hole 48a. Plug 48 is embedded. As a result, the conductive stack 83 is connected to the wiring stack 82, and the seventh and eighth conductive plugs 47 and 48 are electrically connected to the first wiring layers 53 and 54, respectively.

  Next, a metal lid 84 and second wiring layers 57 and 58 are formed on the second interlayer insulating film 38 conductive stack 83 and the seventh and eighth conductive plugs 47 and 48. The metal lid 84 is formed of the same layer as the second wiring layers 57 and 58. Next, a protective film 39 is formed on the second interlayer insulating film 38, the metal lid 84, and the second wiring layers 57 and 58.

  Next, an opening 39 a located on the metal lid 84 is formed in the protective film 39. Next, release holes 84a and 84b are formed in the metal lid 84 exposed by the opening 39a.

  Next, a wet etching solution is supplied to the second interlayer insulating film 38, the first interlayer insulating film 37 and the sacrificial layer 17 through the opening 39 a and the release holes 84 a and 84 b. Thereby, the first and second interlayer insulating films 37 and 38 and the sacrificial layer 17 are removed, and a space 91 is formed in the removed portion. This space 91 is a space covered with the first and second interlayer insulating films 37 and 38 and the sacrificial layer 17, and the MEMS portion 15 is located in the space 91 (see FIG. 5B).

  Thereafter, a metal film 71 (for example, an Al alloy film) is formed by sputtering in the opening 39a, the release holes 84a and 84b, and on the protective film 39, and the metal film 71 on the protective film 39 is patterned. The metal film 71 is embedded in the opening 39a and the release holes 84a and 84b. Thereby, the space 91 is surrounded by the metal film 71, the first and second interlayer insulating films 37 and 38, the sacrificial layer 17, the first silicon nitride film 14, and the metal lid 84, and an airtight structure is formed.

  When the metal film 71 is sputtered, a part of the metal film 71 enters the space 91 below the release hole.

  According to the present embodiment, since the space 61 in which the MEMS unit 15 is disposed is formed by the silicon nitride film and the silicon film 18, it is possible to suppress the generation of gas from the inner wall of the space 61. At the same time, first and second connection holes 21 and 22 are formed in the sacrificial layer 17, the silicon film 18 is embedded in the first and second connection holes 21 and 22, and the first and second connection holes are formed in the silicon film 18. By forming the ring-shaped holes 18a and 18b, the electrode post 18 in the first connection hole 21 is electrically separated from the other silicon film 18, and the electrode post 18 in the second connection hole 22 is electrically separated. Is electrically isolated from the other silicon film 18. Thereby, the electrode post 18 in the first connection hole 21 is electrically connected to the first electrode 15a, and the electrode post 18 in the second connection hole 22 is electrically connected to the second electrode 15b. The As a result, the atmosphere of the space 61 can be suppressed from changing from the initial atmosphere, the reliability of the MEMS element can be improved, and the first and second electrodes 15a and 15b of the MEMS portion are placed outside the space 61. It can be taken out. On the other hand, in the comparative example, a gas is generated from the silicon oxide film on the inner wall of the space 91, the gas is accumulated in the space 91, and the atmosphere of the space 91 varies from the initial atmosphere.

  In the present embodiment, the metal film 71 is formed by embedding the metal film 71 in the second holes 23 and 24 and the release holes 25 and 26 and forming the second interlayer insulating film 38 on the metal film 71. Is completely embedded in the middle of the multilayer metal wiring structure. For this reason, the metal film 71 is not exposed on the protective film 39 of the integrated circuit unit 30. Therefore, the resistance of the MEMS unit 15 against external mechanical stress can be improved.

  Further, in the present embodiment, by forming the MEMS unit 15 together with the integrated circuit unit 30 on the silicon substrate 11, the chip size can be reduced or the manufacturing cost can be reduced.

  In this embodiment, since the volume of the space 61 can be reduced as compared with the comparative example, the time for etching the sacrificial layer 17 can be shortened.

[Embodiment 2]
FIG. 8A is a plan view illustrating a MEMS element according to one embodiment of the present invention, and FIG. 8B is a cross-sectional view taken along line AA ′ illustrated in FIG. In FIG. 8, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description of the same parts is omitted.

  The steps until the first silicon nitride film 14 is formed are the same as those in the first embodiment.

  Next, the MEMS portion 15 is formed on the first silicon nitride film 14. This will be described in detail below.

  A first conductive film is formed on the first silicon nitride film 14, and the first conductive film is patterned, whereby the first electrode 15a, the second electrode 15b, and the second electrode made of the first conductive film are patterned. One silicon base 72 is formed on the first silicon nitride film 14. The first silicon base 72 is formed so as to surround the first and second electrodes 15a and 15b. Next, a gap insulating film similar to that of the first embodiment is formed on the first silicon nitride film 14, the first silicon base 72, and the first and second electrodes 15a and 15b, and this gap insulating film Is patterned. Thus, contact holes 16a, 16b, 16c, and 16d are formed in the gap insulating film. Next, a second conductive film is formed on the entire surface including the gap insulating film, and the second conductive film is patterned, whereby the movable electrode 15c made of the second conductive film, the second silicon stage 73, First and second electrode stands 74 and 75 are formed on the gap insulating film 16. The movable electrode 15c is electrically connected to the first electrode 15a through the contact hole 16c, the first electrode base 74 is electrically connected to the first electrode 15a through the contact hole 16b, and the second electrode base 75 is connected. Is electrically connected to the second electrode 15b through the contact hole 16d, and the second silicon base 73 is disposed on the first silicon base 72 through the contact hole 16a. The second silicon stand 73 is formed so as to surround the movable electrode 15 c and the first and second electrode stands 74 and 75. (See FIG. 8A).

  Thereafter, the gap insulating film is removed by etching as in the first embodiment.

  Next, a sacrificial layer covering the MEMS unit 15, the first and second electrode bases 74 and 75, and the first and second silicon bases 72 and 73 is formed on the first silicon nitride film 14 as in the first embodiment. To form.

  Thereafter, as in the first embodiment, the sacrificial layer is patterned to form the trench 76, the first connection hole 21 and the second connection hole 22 in the sacrificial layer, and the unnecessary sacrificial layer is removed. The groove 76 is located on the second silicon base 73, the first connection hole 21 is located on the first electrode base 74, and the second connection hole 22 is located on the second electrode base 75. . Next, the first silicon nitride film 14 is patterned.

  Next, the integrated circuit portion 30 is formed on the silicon substrate 11 as in the first embodiment.

  Next, as in the first embodiment, a polysilicon film is formed so as to cover the sacrificial layer, and this polysilicon film is patterned. As a result, the silicon film 18 is formed in the trench 76, the silicon film 18 is in close contact with the second silicon base 73 at the bottom of the trench 76, and the silicon film 18 covering the sacrificial layer 17 is formed. The silicon film 18 is formed in the second connection holes 21 and 22, and the silicon film 18 is connected to the first and second electrode bases 74 and 75, and the first and second ring-like shapes are connected to the silicon film 18. Holes 18a and 18b are formed. At this time, the silicon film 18 in the first connection hole 21 is electrically separated from the other silicon film 18 by the first and second ring-shaped holes 18 a and 18 b, and the second connection hole 22. The inner silicon film 18 is electrically isolated from the other silicon films 18. The silicon film 18 in the first connection hole 21 is electrically connected to the first electrode 15a via the first electrode base 74, and the silicon film 18 in the second connection hole 22 is electrically connected to the second electrode hole 74a. It is electrically connected to the second electrode 15b via the electrode table 75. That is, the silicon film 18 positioned inside each of the first and second ring-shaped holes 18a and 18b is electrically connected to the first and second electrodes 15a and 15b of the MEMS unit 15, and is connected to the electrode extraction unit. (See FIGS. 8A and 8B).

  Next, as in the first embodiment, a second silicon nitride film 36 is formed on the entire surface including the insides of the first and second ring-shaped holes 18a and 18b. The subsequent steps are the same as those in the first embodiment. However, by removing the sacrificial layer, after the space 61 is formed in the removed portion, the sacrificial layer 17 is left outside the silicon film 18 embedded in the trench 76 (see FIG. 8B). . Since the remaining sacrificial layer 17 is located outside the inner wall of the space 61, gas is not generated from the inner wall of the space 61.

Also in the present embodiment, the same effect as in the first embodiment can be obtained.
In the present embodiment, the first and second electrode bases 74 and 75 and the first and second silicon bases 72 and 73 are arranged to flatten the silicon film 18 on the ceiling portion above the space 61. can do.

  In the present embodiment, since the silicon film 18 covering the upper portion of the space 61 is formed on the second silicon base 73, the step that the silicon film 18 needs to cover is the step caused by the thickness of the sacrificial material. It does not depend on the thickness of the movable electrode 15c. Therefore, when the thickness of the movable electrode 15c is large, for example, when the thickness of the movable electrode 15c is larger than the thickness of the sacrificial layer in order to obtain various characteristics of the desired MEMS element, the structural reliability and the difficulty of processing of the silicon film 18 are increased. This is more advantageous than the first embodiment.

  In the present embodiment, since the first and second silicon bases 72 and 73 surrounding the periphery of the MEMS unit 15 are provided, the area of the MEMS element is larger than that in the first embodiment shown in FIG. Become. However, in the first embodiment shown in FIG. 1B, it is necessary to take a slope margin around the MEMS unit 15, and when the movable electrode 15c is thick, the slope margin is made large. On the other hand, in this embodiment, since it is not necessary to take such a slope, when the movable electrode 15c is thick, the area of the MEMS element is smaller than that in the first embodiment. . Further, since the etching volume of the sacrificial layer at the time of release is reduced by the amount of such a slope, the processing cost is advantageous compared to the first embodiment.

  In various aspects of the present invention, when a specific B (hereinafter referred to as “B”) is formed above (or below) a specific A (hereinafter referred to as “A”) (B is formed), It is not limited to the case where B is formed directly on (or below) A (B is formed). It includes the case where B is formed (otherwise B) is formed on the upper side (or the lower side) of A through other things as long as the effects of the present invention are not inhibited.

  DESCRIPTION OF SYMBOLS 11 ... Silicon substrate, 12 ... Element isolation film, 13 ... Oxide film, 14 ... 1st silicon nitride film, 15 ... MEMS part, 15a ... 1st electrode, 15b ... 2nd electrode, 15c ... Movable electrode, 16 Insulating film for gap, 16a, 16b, 16c, 16d ... contact hole, 17 ... sacrificial layer, 18 ... silicon film, 18a ... first ring-shaped hole, 18b ... second ring-shaped hole, 21 ... first 1 connection hole, 22 ... second connection hole, 23,24 ... second hole, 25,26 ... release hole, 30 ... integrated circuit portion, 31 ... gate insulating film, 32 ... gate electrode, 33 ... side wall 34 ... Source diffusion layer, 35 ... Drain diffusion layer, 36 ... Second silicon nitride film, 37 ... First interlayer insulating film, 38 ... Second interlayer insulating film, 39 ... Protective film (third insulating film) ), 39a... Opening portion, 41... 3rd connection hole, 42 ... 2nd conductive plug, 42a ... 4th connection hole, 43 ... 3rd conductive plug, 43a ... 5th connection hole, 44 ... 4th conductive plug, 44a ... 6th 45 ... fifth conductive plug, 45a ... seventh connection hole, 46 ... sixth conductive plug, 46a ... eighth connection hole, 47 ... seventh conductive plug, 48 ... eighth conductive. Plug, 51, 52, 53, 54 ... first wiring layer, 55, 56, 57, 58 ... second wiring layer, 61 ... space, 71 ... metal film, 72 ... first silicon base, 73 ... first 2 silicon bases, 74 ... first electrode base, 75 ... second electrode base, 76 ... groove, 81 ... wall-like conductive stack, 81a ... groove, 82 ... wiring stack, 83 ... wall-like conductive stack, 83a ... groove, 84 ... metal lid, 91 ... space, 157,158 ... cap layer.

Claims (11)

A MEMS portion having first and second electrodes is disposed in a space covered with the first silicon nitride film and the silicon film,
The silicon film has first and second ring-shaped holes,
The silicon film located inside the first ring-shaped hole is electrically connected to the first electrode;
The silicon film located inside the second ring-shaped hole is electrically connected to the second electrode;
The MEMS element, wherein each of the first and second ring-shaped holes is filled with a second silicon nitride film. In claim 1,
The MEMS portion is disposed on the first silicon nitride film,
The MEMS element, wherein the silicon film is disposed above the MEMS portion and is in close contact with the first silicon nitride film located around the MEMS portion. In claim 1,
A first electrode base disposed on the first electrode and disposed under the silicon film located inside the first ring-shaped hole;
A second electrode base disposed on the second electrode and disposed under the silicon film located inside the second ring-shaped hole;
A silicon base closely adhered to the first silicon nitride film;
Have
The MEMS portion is disposed on the first silicon nitride film,
The silicon table is located around the MEMS unit,
The MEMS element, wherein the silicon film is disposed above the MEMS unit and is in close contact with the silicon base In any one of Claims 1 thru | or 3,
The silicon film has a first hole;
The first hole is filled with a metal film;
An MEMS device, wherein an airtight structure is formed by the metal film, the silicon film, and the first and second silicon nitride films. In claim 4,
A first insulating film formed on the silicon film;
A second hole formed in the first insulating film and positioned on the first hole;
A second insulating film formed on the first insulating film;
Have
The MEMS element, wherein the first and second holes are filled with the metal film. In claim 4 or 5,
The MEMS element, wherein the first hole is not disposed immediately above the movable electrode of the MEMS portion. In any one of Claims 1 thru | or 6,
The MEMS part is disposed on a semiconductor substrate,
An MEMS device, wherein an integrated circuit is formed on the semiconductor substrate. Forming a MEMS portion having first and second electrodes on the first silicon nitride film;
Forming a sacrificial layer covering the MEMS portion on the first silicon nitride film;
Forming a first connection hole located on the first electrode and a second connection hole located on the second electrode in the sacrificial layer;
Forming a silicon film on the first silicon nitride film located around the sacrificial layer, and in the first and second connection holes and covering the sacrificial layer;
The silicon film in the first connection hole is separated by forming a first ring-shaped hole in the silicon film, and the second ring-shaped hole is formed in the silicon film by forming the second ring-shaped hole. Separating the silicon film in the two connection holes;
Filling the first and second ring-shaped holes with a second silicon nitride film;
Forming a first hole in the silicon film;
By removing the sacrificial layer by supplying a wet etchant to the sacrificial layer through the first hole, a MEMS portion is formed in the space covered with the first and second silicon nitride films and the silicon film. A method for manufacturing a MEMS device, wherein the MEMS device is positioned. Forming a MEMS portion having first and second electrodes on the first silicon nitride film;
Forming a sacrificial layer covering the MEMS portion on the first silicon nitride film;
Forming a first connection hole located on the first electrode and a second connection hole located on the second electrode in the sacrificial layer;
Forming a silicon film on the first silicon nitride film located around the sacrificial layer, and in the first and second connection holes and covering the sacrificial layer;
The silicon film in the first connection hole is separated by forming a first ring-shaped hole in the silicon film, and the second ring-shaped hole is formed in the silicon film by forming the second ring-shaped hole. Separating the silicon film in the second connection hole and forming the first hole;
Burying the first hole, the first and second ring-shaped holes with a second silicon nitride film,
Removing the second silicon nitride film embedded in the first hole;
By removing the sacrificial layer by supplying a wet etchant to the sacrificial layer through the first hole, a MEMS portion is formed in the space covered with the first and second silicon nitride films and the silicon film. A method for manufacturing a MEMS device, wherein the MEMS device is positioned. In claim 8 or 9,
The MEMS unit has a movable electrode,
When forming the MEMS portion, the first and second electrodes and the first silicon base surrounding the first and second electrodes are formed on the first silicon nitride film, and then the first silicon stand is formed. Forming a first electrode base on the first electrode, forming the movable electrode and the second electrode base on the second electrode, and forming a second silicon base on the first silicon base,
When forming the sacrificial layer covering the MEMS portion, the sacrificial layer covering the first and second electrode bases and the first and second silicon bases is formed on the first silicon nitride film,
When forming the first and second connection holes in the sacrificial layer, the sacrificial layer is positioned on the first electrode hole and the second electrode table located on the first electrode table. Forming a groove located on the second connection hole and the second silicon base,
When forming the silicon film, forming the silicon film in the groove,
A method of manufacturing a MEMS device, wherein the sacrificial layer is removed to position the MEMS portion, the first and second electrode bases, and the first and second silicon bases in the space. In any one of Claims 8 to 10,
After removing the sacrificial layer, the space is sealed by embedding a metal film in the first hole by sputtering.

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