JP4501715B2 - MEMS element and method for manufacturing MEMS element - Google Patents

Description

  The present invention relates to a MEMS element and a method for manufacturing the MEMS element.

  2. Description of the Related Art In recent years, sensors, resonators, communication devices, and the like that have MEMS devices on a semiconductor substrate using MEMS (Micro Electro Mechanical System) technology have attracted attention. The MEMS element is a functional element made of a minute structure manufactured on a semiconductor substrate using a semiconductor manufacturing process. This structure includes a movable portion (movable electrode) of a cantilever beam or a double-supported beam structure that is deformed by an external force such as an electric force or acceleration, and a fixed portion (fixed electrode). For example, a MEMS device including a comb-like movable electrode and a comb-like fixed electrode as shown in Patent Document 1 is known.

JP 2004-276200 A

  In such a MEMS element, when a wiring for taking out an electrical signal of a structure or a circuit element is formed on the same semiconductor substrate, a wiring layer is stacked on the periphery of the structure. . Specifically, this will be described with reference to FIG. FIG. 7 is a cross-sectional view showing a MEMS element having the above configuration.

  As shown in FIG. 7, in the MEMS element 100, a lower electrode 102 is formed on a semiconductor substrate 101, and a structure 110 is formed thereon. Further, the wiring part 120 is formed so as to surround the structure 110. In manufacturing the MEMS element 100, the insulating film 103, the structure forming film 112, the interlayer insulating film 104, the wiring 105, the interlayer insulating film 106, and the passivation film 107 are sequentially stacked on the semiconductor substrate 101. Finally, The passivation film 107, the interlayer insulating film 106, the interlayer insulating film 104, and the insulating film 103 above the structure 110 are etched to provide an opening 111, and the structure 110 is released.

  However, in the MEMS element 100 having such a configuration, the interlayer insulating films 106 and 107 are exposed on the side wall of the opening 111 after the structure 110 is released. For this reason, moisture is likely to enter from the exposed interlayer insulating films 106 and 107, and this moisture is expected to damage the wiring and significantly reduce the reliability of the MEMS element 100.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a MEMS element having good moisture resistance and improved reliability and a method for manufacturing the MEMS element.

The method for manufacturing a MEMS device of the present invention includes a step of forming an insulating film on a semiconductor substrate, a step of forming a lower electrode on the semiconductor substrate, a first portion of the insulating film located on the lower electrode, and the Etching a second part surrounding the first part to form a first groove in the first part and a second groove in the second part; and on the insulating film, the first groove and the second part Forming a structure forming film in the groove; and patterning the structure forming film to form the structure on the first groove and the first groove, and the structure on the second groove and the second groove. Forming a surrounding first guard ring; forming a first interlayer insulating film on the structure and on the first guard ring; and the first interlayer insulation positioned on the first guard ring. A membrane surrounding the structure Forming a groove, forming a second guard ring surrounding the structure on the third groove and the third groove, and outside the region on the first interlayer insulating film and surrounded by the second guard ring Forming the wiring on the second guard ring and on the wiring, forming the second interlayer insulating film on the second guard ring, and forming the structure on the second interlayer insulating film located on the second guard ring. Forming a fourth groove surrounding the body, forming a third guard ring surrounding the structure on the fourth groove and the fourth groove, and forming a passivation film on the third guard ring. And forming the opening by first etching the passivation film and the second interlayer insulating film above the structure until the surface of the structure is exposed, and the first under the opening. Interlayer Characterized in that it comprises a Enmaku and step of second etching the insulating film.
  The MEMS element manufacturing method of the present invention is the MEMS element manufacturing method, wherein the first guard ring is a through base guard ring located in the same layer as the insulating film, and the structure on the first groove. The second guard ring is composed of a through guard ring located in the same layer as the first interlayer insulating film and a guard ring located in the same layer as the wiring. It is characterized by that.
  The MEMS element manufacturing method of the present invention is characterized in that, in the MEMS element manufacturing method, the first etching is dry etching and the second etching is wet etching.
  Moreover, the manufacturing method of the MEMS element of this invention is the manufacturing method of the said MEMS element. In any one of Claim 1 thru | or 3, The said structure and the said 1st guard ring have a polysilicon, The said 2nd The guard ring and the wiring have a first metal, and the third guard ring has a second metal.
  Moreover, the MEMS element of the present invention includes a semiconductor substrate, a structure formed on the semiconductor substrate,
  An insulating film that surrounds the structure in plan view, a first through guard ring that passes through the insulating film and surrounds the structure in plan view, and is formed on the first through guard ring. A first guard ring that surrounds the body; a first interlayer insulating film that is formed on the first guard ring and that surrounds the structure in plan view; and the first interlayer insulating film that is formed on the first guard ring. A second penetrating guard ring that surrounds the structure in plan view,
  A second guard ring formed on the second through guard ring; a wiring formed on the first interlayer insulating film and outside an area surrounded by the second guard ring in a plan view;
  A second interlayer insulating film formed on the second guard ring and surrounding the structure in plan view; and formed on the second guard ring and penetrating through the second interlayer insulating film; A third through guard ring that surrounds the body, and a third guard ring that is formed on the third through guard ring and surrounds the structure in plan view, the structure, the first through guard ring, and the The first guard ring has polysilicon.
  The MEMS element of the present invention is the MEMS element, wherein the second through guard ring, the second guard ring, and the wiring include Al or Cu, and the third through guard ring and the third guard ring Is characterized by containing Al or Cu.

The MEMS element of the present invention is a MEMS element including a wiring portion in which a structure is formed on a semiconductor substrate, and a wiring and an interlayer insulating film are stacked around the structure around the structure. A guard ring having a shape surrounding the structure in a plan view is formed between the films constituting the wiring portion, and a penetrating guard ring penetrating each film and contacting the entire circumference with the guard ring positioned vertically The wirings formed and arranged in the wiring part are arranged outside the guard rings and the penetrating guard rings.
According to this configuration, the guard ring is formed between the films constituting the wiring portion so as to surround the structure in a plan view, and the penetrating guard ring is a guard ring that penetrates each film and is positioned above and below. It is formed to touch the entire circumference. In this way, the guard ring and the through guard ring are formed as partition walls that guard the wiring of the wiring portion. And since the wiring is arranged outside the guard ring and the through guard ring, the moisture that has entered from the exposed interlayer insulating film of the wiring portion is a portion where the wiring is arranged by the guard ring and the through guard ring as a barrier. It is possible to prevent moisture from entering. From this, it is possible to provide a MEMS element having good moisture resistance and improved reliability without being affected by moisture.

  In the MEMS element of the present invention, it is preferable that the lowermost guard ring and the through guard ring are made of polysilicon, and the other guard ring and the through guard ring are made of metal.

  According to this configuration, the lowermost guard ring and the through guard ring can be manufactured in the same process as the process of forming the structure, and the other guard ring and the through guard ring are the process of forming the wiring. Manufacture is possible in the same process. In this way, the manufacturing process can be simplified.

  The method for manufacturing a MEMS element according to the present invention is a method for manufacturing a MEMS element comprising: a structure on a semiconductor substrate; and a wiring portion in which a wiring and an interlayer insulating film are stacked so as to surround the structure around the structure. A step of forming an insulating film on a semiconductor substrate; a step of forming a lower electrode on the semiconductor substrate; a step of forming a structure forming film on the insulating film; and etching the structure forming film. A step of forming a shape of a structure, a step of forming a base guard ring at a position in the same layer as the structure forming film of the wiring portion, and a step of forming a base through guard ring at a position in the same layer as the insulating film; An interlayer insulating film and a wiring are formed above the structure forming film, a guard ring is formed at the same layer as the wiring, and the interlayer insulating film is penetrated at the same layer as the interlayer insulating film. Form a penetration guard ring A step of laminating each of them, a step of forming a passivation film above the uppermost guard ring, and etching the passivation film and the interlayer insulating film above the structure to at least the surface of the structure to form openings. And a step of etching the film below the surface of the structure as a sacrificial layer to release the structure.

  According to such a manufacturing method of the MEMS element, the guard ring and the through guard ring serve as a barrier, and moisture can be prevented from entering from the exposed interlayer insulating film of the wiring portion. From this, it is possible to provide a method of manufacturing a MEMS element having good moisture resistance and improved reliability without being affected by moisture.

  In the method for manufacturing a MEMS element of the present invention, it is preferable that the base guard ring and the base through guard ring are formed in the same step as the step of forming the shape of the structure.

  If it does in this way, a structure, a base guard ring, and a base penetration guard ring can be manufactured in the same process, and a manufacturing process can be reduced.

  In the method for manufacturing a MEMS element of the present invention, it is preferable that the guard ring and the through guard ring are formed in the same step as the step of forming the wiring.

  If it does in this way, wiring, a guard ring, and a penetration guard ring can be manufactured in the same process, and a manufacturing process can be reduced.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings.
(First embodiment)

  FIG. 1 is a schematic configuration diagram showing an embodiment of a MEMS resonator as a MEMS element according to the present invention. FIG. 1A is a plan view of a MEMS element, and FIG. 1B is a cross-sectional view taken along the line AA in FIG.

  In FIG. 1, in the MEMS element 1, a structure 18 composed of a movable electrode 15 made of polysilicon and fixed electrodes 16a and 16b is formed in an opening 39 on a semiconductor substrate 10 made of silicon. An n-type lower electrode 13 is formed on the semiconductor substrate 10 and is electrically connected to the structure 18. In addition, an insulating film 11 that is a thermal oxide film formed on the semiconductor substrate 10 is formed on the peripheral wiring portion 40 facing the structure 18, and an interlayer insulating film 20, wiring 21, and interlayer insulation are formed thereon. A film 22 and a passivation film 23 are sequentially stacked. The wiring 21 is made of Al, Cu, or the like, and is connected to a circuit element formed on the lower electrode 13 or the semiconductor substrate 10 (not shown).

  A base guard ring 31 made of polysilicon is formed between the insulating film 11 and the interlayer insulating film 20 of the wiring portion 40, and made of polysilicon that penetrates the insulating film 11 from the base guard ring 31 and contacts the semiconductor substrate 10. A base penetration guard ring 30 is formed. These are formed in a shape surrounding the structure 18 in plan view as shown in the plan view of FIG.

A guard ring 33 made of Al or Cu is formed between the interlayer insulating film 20 and the interlayer insulating film 22, and Al or Cu that penetrates the interlayer insulating film 20 from the guard ring 33 and makes contact with the base guard ring 31. A penetration guard ring 32 made of Cu is formed.
Further, a guard ring 35 made of Al or Cu is formed between the interlayer insulating film 22 and the passivation film 23. The guard ring 35 penetrates the interlayer insulating film 22 from the guard ring 35 and contacts the guard ring 33 all around. A through guard ring 34 is formed.
Similar to the base guard ring 31 and the base penetration guard ring 30, these are formed in a shape surrounding the structure 18 in plan view.

  Thus, the MEMS element 1 has the structure 18 and the wiring part 40 on the semiconductor substrate 10, and the base guard ring 31, the guard ring 33, and the guard ring 33 are formed on the insulating film 11 and the interlayer insulating films 20 and 22 of the wiring part 40. 35 is formed, and a base through guard ring 30 and through guard rings 32 and 34 are formed so as to connect the semiconductor substrate 10 to each other. The wiring 21 is disposed outside the base guard ring 31, the guard rings 33 and 35, the base penetration guard ring 30, and the penetration guard rings 32 and 34.

  In the MEMS element 1 having the above-described configuration, an AC voltage is applied between one fixed electrode 16a and a ground electrode (not shown), so that the static electricity is generated between the comb-shaped fixed electrode 16a and the movable electrode 15. Electric power is generated to cause the movable electrode 15 to vibrate in a plane, and the resonance frequency of this vibration is taken out from the other fixed electrode 16b.

As described above, in the MEMS element 1 of the present embodiment, the wiring 21 is arranged outside the guard rings 31, 33, 35 and the through guard rings 30, 32, 34, so that the interlayer insulating film exposed at the opening 39 is used. Moisture that has entered from 22 and 20 is protected by the guard rings 31, 33, and 35 and the through guard rings 30, 32, and 34, thereby protecting the wiring 21 from moisture. For this reason, the moisture resistance of the MEMS element 1 can be improved and the reliability can be improved.
(Second Embodiment)

Next, a method for manufacturing a MEMS element will be described. In manufacturing the MEMS element, a semiconductor CMOS process is used.
2, 3, and 4 are schematic cross-sectional views illustrating the manufacturing process of the MEMS element 1.

First, in FIG. 2A, an insulating film 11 which is a thermal oxide film (SiO ₂ film) is formed on a semiconductor substrate 10 made of silicon, and a photoresist is applied thereon to form a photoresist film 12. Then, the photoresist film 12 is patterned into a predetermined shape. Thereafter, as shown in FIG. 2B, P ions are implanted from above the patterned semiconductor substrate 10 to form an n-type lower electrode 13 on the semiconductor substrate 10. Next, the photoresist film 12 is removed, a photoresist is applied again, and patterning is performed to remove a part of the insulating film 11 above the lower electrode 13 and in a region where a wiring portion is to be formed. Then, as shown in FIG. 2C, a part of the insulating film 11 is etched to the surface of the semiconductor substrate 10 by etching, and the photoresist is removed. Next, as shown in FIG. 2D, a structure forming film 14 made of polysilicon is formed from above. At this time, the polysilicon wraps around the portion from which a part of the insulating film 11 is removed.

  Next, as shown in FIG. 3A, the structure forming film 14 is patterned to form the structures 18 (the movable electrode 15 and the fixed electrodes 16a and 16b), the base through guard ring 30, and the base guard ring 31. Isolate. FIG. 5 is a schematic plan view showing the shape and arrangement of the structure 18, the base through guard ring 30, and the base guard ring 31. The movable electrode 15 and the fixed electrodes 16a and 16b constituting the structure 18 have comb-like protrusions and are arranged so as to engage with each other. The base penetration guard ring 30 is in contact with the base guard ring 31 all around. And the base penetration guard ring 30 and the base guard ring 31 are formed so that the structure 18 may be enclosed in planar view.

Next, as shown in FIG. 3B, an interlayer insulating film 20 such as a SiO ₂ film is formed on the structure 18 and the base guard ring 31. Subsequently, as shown in FIG. 3C, a part of the interlayer insulating film 20 on the base guard ring 31 is patterned to form a groove 25 reaching the surface of the base guard ring 31. FIG. 6 is a schematic plan view showing the arrangement of the groove portions 25, and the groove portions 25 are formed so as to surround the structure 18 in a plan view.
Thereafter, as shown in FIG. 3D, a film such as Al or Cu is formed on the interlayer insulating film 20 and patterned to form the wiring 21, the through guard ring 32, and the guard ring 33. Then, an interlayer insulating film 22 is formed thereon. The wiring 21 is connected to the lower electrode 13 provided on the semiconductor substrate 10 or a circuit element provided on the semiconductor substrate 10.

Next, as shown in FIG. 4A, a part of the interlayer insulating film 22 on the guard ring 33 is patterned to form a groove portion 26 that reaches the surface of the guard ring 33. The groove 26 is formed so as to surround the structure 18 in plan view.
Thereafter, as shown in FIG. 4B, a film such as Al or Cu is formed on the interlayer insulating film 22 and patterned to form a through guard ring 34 and a guard ring 35. Then, a passivation film 23 such as a silicon nitride (Si ₃ N ₄ ) film is formed thereon.

Next, as shown in FIG. 4C, the passivation film 23 and the interlayer insulating film 22 located above the structure 18 are anisotropically etched (dry etching) to form an opening 38. This anisotropic etching is performed until at least the surface of the structure 18 is exposed.
Subsequently, as shown in FIG. 4D, isotropic etching (wet etching) is performed using the interlayer insulating film 20 and the insulating film 11 below the surface of the structure 18 as a sacrificial layer to form an opening 39. Release body 18.

An etching gas such as CF ₄ is used for anisotropic etching of the passivation film 23. In addition, a fluorine-based or chlorine-based etching gas is used for anisotropic etching of the interlayer insulating films 20 and 22, and a hydrofluoric acid-based etching solution is used for isotropic etching of the interlayer insulating film 20 and the insulating film 11. It is done.

  As described above, according to the method for manufacturing the MEMS element 1 of the present embodiment, since the wiring 21 is disposed outside the guard rings 31, 33, and 35 and the through guard rings 30, 32, and 34, the opening 39 is provided. Moisture that has entered through the interlayer insulating films 22 and 20 exposed in FIG. 4 becomes a barrier by the guard rings 31, 33, and 35 and the through guard rings 30, 32, and 34, thereby protecting the wiring 21 from moisture. For this reason, the moisture resistance of the MEMS element 1 can be improved and the reliability can be improved.

Further, by forming the structure 18, the base guard ring 31, and the base through guard ring 30 with polysilicon, each can be manufactured in the same process, and the manufacturing process can be reduced and the process can be simplified.
Similarly, if the wiring 21, the guard rings 33 and 35, and the through guard rings 32 and 34 are made of metal such as Al and Cu, each can be manufactured in the same process, reducing the manufacturing process, Simplification can be achieved.

  In addition, the wiring laminated | stacked on the wiring part 40 may be laminated | stacked on multiple layers, In that case, a guard ring and a penetration guard ring can be formed in multiple layers between each interlayer insulation film, and wiring can be protected from moisture. .

  Further, in the present embodiment, the structure, the base through guard ring, and the base guard ring are formed of polysilicon, but the present invention can also be implemented using another gate electrode material silicided in a CMOS transistor.

  In the embodiment of the present invention, the MEMS resonator has been described as an example. However, the present invention can be implemented in an actuator, a gyro sensor, and an acceleration sensor using the MEMS technology, and the same effect can be obtained.

It is a schematic block diagram of the MEMS element by embodiment of this invention, (a) is a top view of a MEMS element, (b) is sectional drawing which follows the AA disconnection of the figure (a). The schematic sectional drawing which shows the manufacturing process of a MEMS element. The schematic sectional drawing which shows the manufacturing process of a MEMS element. The schematic sectional drawing which shows the manufacturing process of a MEMS element. The schematic plan view which shows the shape and arrangement | positioning of a structure, a base penetration guard ring, a base guard ring. The schematic plan view which shows the shape and arrangement | positioning of the groove part formed in an interlayer insulation film. The schematic sectional drawing of the MEMS element explaining the subject which invention intends to solve.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... MEMS element, 10 ... Semiconductor substrate, 11 ... Insulating film, 12 ... Photoresist film, 13 ... Lower electrode, 14 ... Structure formation film, 15 ... Movable electrode which comprises structure, 16a, 16b ... Structure Constituting fixed electrode, 18 ... structure, 20 ... interlayer insulating film, 21 ... wiring, 22 ... interlayer insulating film, 23 ... passivation film, 30 ... base through guard ring as through guard ring, 31 ... base as guard ring Guard ring, 32, 34 ... penetrating guard ring, 33, 35 ... guard ring, 39 ... opening, 40 ... wiring part.

Claims (6)

Forming an insulating film on the semiconductor substrate;
  Forming a lower electrode on the semiconductor substrate;
  By etching the first portion of the insulating film located on the lower electrode and the second portion surrounding the first portion, the first groove is formed in the first portion and the second groove is formed in the second portion. Process,
  Forming a structure forming film on the insulating film in the first groove and the second groove;
  Patterning the structure forming film to form a structure on the first groove and the first groove and a first guard ring surrounding the structure on the second groove and the second groove;
  Forming a first interlayer insulating film on the structure and the first guard ring;
  Forming a third groove surrounding the structure in the first interlayer insulating film located on the first guard ring;
  Forming a second guard ring surrounding the structure on the third groove and the third groove, and forming a wiring on the first interlayer insulating film outside the region surrounded by the second guard ring; ,
  Forming a second interlayer insulating film on the second guard ring and on the wiring;
  Forming a fourth groove surrounding the structure in the second interlayer insulating film located on the second guard ring;
  Forming a third guard ring surrounding the structure on the fourth groove and the fourth groove;
  Forming a passivation film on the third guard ring;
  Forming an opening by first etching the passivation film and the second interlayer insulating film above the structure until the surface of the structure is exposed;
  And a second etching step of the first interlayer insulating film and the insulating film below the opening. In claim 1,
  The first guard ring includes a penetrating base guard ring located in the same layer as the insulating film, and a base guard ring located in the same layer as the structure on the first groove,
  The method of manufacturing a MEMS element, wherein the second guard ring includes a through guard ring located in the same layer as the first interlayer insulating film and a guard ring located in the same layer as the wiring. In claim 1 or 2,
  The first etching is dry etching,
  The method of manufacturing a MEMS device, wherein the second etching is wet etching. In any of claims 1 to 3,
  The structure and the first guard ring have polysilicon,
  The second guard ring and the wiring have a first metal,
  The method of manufacturing a MEMS device, wherein the third guard ring includes a second metal. A semiconductor substrate;
  A structure formed on the semiconductor substrate;
  An insulating film surrounding the structure in plan view;
  A first through guard ring penetrating the insulating film and surrounding the structure in plan view;
  A first guard ring formed on the first through guard ring and surrounding the structure in plan view;
  A first interlayer insulating film formed on the first guard ring and surrounding the structure in plan view;
  A second through guard ring formed on the first guard ring, penetrating the first interlayer insulating film and surrounding the structure in plan view;
  A second guard ring formed on the second through guard ring;
  A wiring formed on the first interlayer insulating film and outside the region surrounded by the second guard ring in plan view;
  A second interlayer insulating film formed on the second guard ring and surrounding the structure in plan view;
  A third penetrating guard ring formed on the second guard ring, penetrating the second interlayer insulating film and surrounding the structure in plan view;
  A third guard ring formed on the third through guard ring and surrounding the structure in plan view,
  The MEMS element, wherein the structure, the first through guard ring, and the first guard ring include polysilicon. In claim 5,
  The second through guard ring, the second guard ring and the wiring have Al or Cu;
  The MEMS element, wherein the third through guard ring and the third guard ring include Al or Cu.

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