JP2014018871A - Process monitor element, and method for manufacturing mems element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process monitor element in which a gauge for monitoring degrees of release etching in a MEMS element manufacturing process does not become a particle to stably monitor a degree of release etching.SOLUTION: A process monitor element 100 is one in a MEMS element manufacturing process for forming a plurality of MEMS elements having MEMS vibrators to be formed by performing release etching to a sacrifice layer on a principal plane of a wafer substrate 1, and comprises: a monitor sacrifice layer 30 which is distributed on the principal plane of the wafer substrate 1 and is composed of the sacrifice layer; a resist layer 31 laminated on the monitor sacrifice layer 30; an etching hole 32 which is formed in the resist layer 31 to expose the monitor sacrifice layer 30; and a gauge 40 by which a position of an etching interface 30a of the monitor sacrifice layer 30 etched by etching liquid to be introduced from the etching hole 32 is relatively watched from the principal plane side of the wafer substrate 1.

Description

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

Generally, an electromechanical structure including a mechanically movable structure called a MEMS (Micro Electro Mechanical System) device formed by utilizing microfabrication technology, such as a vibrator, a filter, a sensor, and a motor. Are known.
An example of a method for manufacturing a MEMS device will be described. For example, in the case of a vibrator, first, a fixed electrode and a movable part partially formed on a sacrificial layer are formed on a wafer substrate such as silicon via an insulating layer. An electrode is formed, and a wiring laminated portion including wiring is formed on the fixed electrode and the movable electrode. Next, a part of the wiring laminated portion and the sacrificial layer is removed by etching, and the movable electrode having a cantilever or a double-supported beam structure is released, thereby forming a movable electrode in a mechanically movable state.
Among such MEMS devices, in the case of such a vibrator, the basic characteristics such as the resonance frequency greatly depend on the dimensional accuracy of the movable electrode and its support part, and therefore the etching finish confirmation is an important quality control element. . For example, when the etching is insufficient, the predetermined characteristics cannot be obtained, and when the etching is excessive, the reliability is reduced due to the etching up to the wiring laminated portion.
On the other hand, for example, as described in Patent Document 1, a monitor element including a plurality of monitor fingers that can visually confirm the degree of etching quantitatively has been proposed. This is because the MEMS element and the monitor element are mixedly arranged on the wafer substrate, and the monitor finger provided on the monitor element is used as the etching amount scale, and the position of the boundary surface between the monitor finger and the etching is visually confirmed with a microscope or the like. By doing this, the release etching range of the MEMS structure can be confirmed.

JP 2007-83341 A

  However, the monitor element described in Patent Document 1 has a problem in that a monitor finger for visually recognizing the degree of etching is actually etched, so that a piece of the monitor finger may become a contamination source as particles. . Specifically, the monitor finger released in a cantilever state is easily released in a subsequent cleaning process or the like, and becomes a particle when it falls off as a fragment and scatters.

  The present invention has been made to solve the above-described problems, and can be implemented as the following application examples or forms.

  Application Example 1 A process monitor element according to this application example is a process monitor in a MEMS element manufacturing process in which a plurality of MEMS elements having a MEMS structure formed by etching a sacrificial layer are formed on the main surface of a wafer substrate. An element, the sacrificial layer disposed on the main surface of the wafer substrate, made of a monitor sacrificial layer, a resist layer laminated on the monitor sacrificial layer, and formed on the resist layer. An exposed etching hole; and a gauge capable of viewing the position of the etching interface of the monitor sacrificial layer etched by the etching solution introduced from the etching hole relative to the main surface side of the wafer substrate. .

According to the process monitor element of the present application example, since the gauge that can be viewed from the main surface side of the wafer substrate is provided with the gauge that allows the position of the etched monitor sacrificial layer to be viewed from the main surface side, the etching is performed to form the MEMS structure. The degree of (release etching) can be visually recognized.
More specifically, an etching hole for introducing an etchant is provided in the resist layer laminated on the monitor sacrificial layer (that is, the process monitor element of this application example is prepared), and release etching for forming the MEMS structure. At the same time, the monitor sacrificial layer is etched with an etchant introduced from the etching hole. The progress of the etching of the monitor sacrificial layer based on the exposed portion by the etching hole can be visually recognized as an etching interface of the monitor sacrificial layer that penetrates the resist layer and gradually spreads in accordance with the etching time. By comparing the position of the etching interface with a gauge provided in the process monitor element, it becomes possible to confirm the progress of release etching for forming the MEMS structure that has proceeded at the same time. In addition, when the progress of the etching of the monitor sacrificial layer and the progress of the release etching for forming the MEMS structure are not 1: 1, that is, when the etching speed is different, the speed ratio is previously set. By evaluating the above, it is possible to determine the degree of progress of release etching for a relatively accurate MEMS structure.
As a result, the management of the etching dimensional accuracy for forming the predetermined MEMS structure can be performed more easily and accurately.

  Application Example 2 In the process monitor element according to the application example, the gauge is formed on an outer peripheral portion of the region of the monitor sacrificial layer that is etched by the etchant at least within a predetermined time. To do.

  According to this application example, the gauge is formed at the outer peripheral portion of the region of the monitor sacrificial layer that is etched at least within a predetermined time by the etching solution, that is, at a position not included in the region to be etched. In the predetermined time, it is not affected by etching. Therefore, in the method in which the release etching for forming the MEMS structure is sufficiently completed within a predetermined time, the gauge is not affected by the etching, and thus the progress degree of the release etching can be visually recognized stably. . Also, since the gauge is not affected by etching, it does not cause particles.

  Application Example 3 In the process monitor element according to the application example described above, the gauge is a scale pattern formed in a step of patterning an electric wiring layer included in the MEMS element.

  According to this application example, the gauge is a scale pattern formed in the step of patterning the electric wiring layer included in the MEMS element, and therefore it is not necessary to newly provide a step for forming a scale pattern as a gauge. . For example, when the electric wiring layer of the MEMS element is formed with a metal pattern by photolithography, the scale can be simultaneously formed with the metal pattern, so that the process can be simplified.

  Application Example 4 In the process monitor element according to the application example described above, the gauge is a scale pattern formed in a step of patterning a base layer forming the MEMS structure.

  According to this application example, since the gauge is a scale pattern formed in the step of patterning the base layer forming the MEMS structure, it is necessary to newly provide a step for forming a scale pattern as a gauge. No. For example, when a vibrator as a base layer of a MEMS element is formed of polysilicon by photolithography, for example, a scale by a polysilicon pattern is formed at the same time, so that the process can be simplified.

  Application Example 5 In the process monitor element according to the application example, the monitor sacrificial layer is provided on the monitor sacrificial layer so as to separate the adjacent MEMS element on the main surface of the wafer substrate. The etching rate of the etching solution with respect to the wall portion is lower than the etching rate of the etching solution with respect to the sacrificial layer.

  According to this application example, the monitor sacrificial layer has a wall portion provided in the monitor sacrificial layer so as to separate the adjacent MEMS element on the main surface of the wafer substrate, and the wall portion is etched. The etching rate by the liquid is made of a material smaller than the etching rate for the material constituting the sacrificial layer. Therefore, for example, even when the etching is performed for a predetermined time or longer, the progress of the etching at the wall portion can be suppressed, so that the influence on the adjacent MEMS element can be reduced. Specifically, when the wall portion is configured as an etching stopper, the etching effect on the MEMS element adjacent to the wall portion is suppressed even when the etching is performed for a predetermined time. Therefore, the influence of the process monitor element on the adjacent MEMS element can be suppressed.

  Application Example 6 In the process monitor element according to the application example described above, the wall portion provided in the monitor sacrificial layer includes a wall provided in the sacrificial layer for forming the MEMS structure by release etching. It is formed by the same structure as a part.

  According to this application example, the wall portion provided in the monitor sacrificial layer is preferably formed in the same configuration as the wall portion provided in the sacrificial layer for forming the MEMS structure by release etching. Since the same structure can be used at the same time, there is no need to newly provide a process for forming the wall portion of the process monitor element.

  Application Example 7 In the process monitor element according to the application example described above, a region of the monitor sacrificial layer that is etched by the etchant at least within a predetermined time is electrically connected to an electrical wiring layer included in the MEMS element. It is characterized by being laminated on a conductive layer.

  According to this application example, the region of the monitor sacrificial layer that is etched at least within a predetermined time is formed by being stacked on the conductive layer that is electrically connected to the electric wiring layer included in the MEMS element. Therefore, for example, after the etching process is performed, the resist layer is peeled off, and the metal pattern including the etched monitor sacrificial layer is laminated, thereby electrically connecting to the electric wiring layer provided in the MEMS element. An electrode pad portion to be formed can be configured. In other words, the electrode pad portion included in the MEMS element can be configured as the process monitor element described above.

  Application Example 8 In the process monitor element according to the application example described above, the region of the monitor sacrificial layer etched at least within a predetermined time by the etchant is stacked on a conductive layer that can be electrically connected to an external electric circuit. It is characterized by being formed by being laminated on an insulating layer.

  According to this application example, the region of the monitor sacrificial layer that is etched at least within a predetermined time is formed by being laminated on the insulating layer that is laminated on the conductive layer that can be electrically connected to the external electric circuit. Therefore, for example, after performing the etching process, the resist layer is peeled off, and a metal pattern including the etched monitor sacrificial layer is laminated to form a conductive layer that can be electrically connected to an external electric circuit. A capacitor structure (capacitor) having an insulating layer therebetween can be formed. In other words, the part forming the capacitor can be configured as the process monitor element described above.

  Application Example 9 In the process monitor element according to the application example described above, the wall portion is configured to include a conductive material, and when the wafer substrate is viewed in plan, the wall portion is electrically connected to a portion surrounding the monitor sacrificial layer. One end portion of the wall portion that is provided continuously with the insulating portion so as to surround the monitor sacrificial layer and that contacts the insulating portion is a terminal that can be electrically connected to an external electric circuit. The other end of the wall portion that is electrically connected and abuts against the insulating portion is electrically connected to a conductive layer on which the region of the monitor sacrificial layer that is etched within the predetermined time by the etchant is stacked. It is characterized by being connected to.

  According to this application example, the wall portion is configured to include a conductive material, and when the wafer substrate is viewed in plan, the wall portion includes an insulating portion that is electrically insulated in a part surrounding the monitor sacrificial layer. One end of the wall portion that is continuously formed so as to surround the insulating portion and is in contact with the insulating portion is electrically connected to a terminal that can be electrically connected to the external electric circuit, and the wall portion that is in contact with the insulating portion is The other end is electrically connected to a conductive layer on which a region of the monitor sacrificial layer that is etched by the etchant at least within a predetermined time is stacked. Therefore, for example, after performing the etching process, the resist layer is peeled off, and a metal pattern including the etched monitor sacrificial layer region is laminated so as to surround the remaining monitor sacrificial layer without being etched. It is possible to form a coil structure that wraps around. In other words, the part forming the coil structure can be configured as the process monitor element described above.

  Application Example 10 In the process monitor element according to the application example described above, pieces having a plurality of different lengths released by the etching in the region of the monitor sacrificial layer etched at least within a predetermined time by the etchant. A beam having a cantilever structure is formed.

According to this application example, a cantilever beam having a plurality of different lengths released by etching is formed in the region of the monitor sacrificial layer etched at least within a predetermined time. With this configuration, for example, when the MEMS element includes a cantilever beam having the same configuration as the cantilever beam formed on the process monitor element as the MEMS structure, the monitor is used. The progress of the sacrificial layer etching and the progress of the release etching for forming the MEMS structure can be more approximated. Therefore, it is possible to manage the etching dimensional accuracy with higher accuracy.
In addition, by forming a plurality of cantilever beams having different lengths, it is possible to perform cleaning subsequent to release etching, evaluation of beam sticking in a drying process, and the like. In other words, the part for evaluating the sticking of the beam can be configured as the process monitor element described above.

  Application Example 11 A method for manufacturing a MEMS device according to this application example includes a step of forming a process monitor element according to the application example, a step of etching the sacrificial layer including the monitor sacrificial layer, and the sacrificial monitor And confirming a release range of the MEMS structure by viewing a position of an etching interface formed by etching a layer relative to the gauge.

According to this application example, in the manufacturing process of the MEMS element, by utilizing the process monitor element according to the application example, the degree of release etching for forming the MEMS structure is visually recognized later in the release etching process. Can do.
More specifically, an etching hole for introducing an etchant is provided in the resist layer laminated on the monitor sacrificial layer (that is, the process monitor element of this application example is prepared), and release etching for forming the MEMS structure. At the same time, the monitor sacrificial layer is etched with an etchant introduced from the etching hole. The progress of the etching of the monitor sacrificial layer based on the exposed portion by the etching hole can be visually recognized as an etching interface of the monitor sacrificial layer that penetrates the resist layer and gradually spreads in accordance with the etching time. By comparing the position of the etching interface with a gauge provided in the process monitor element, it is possible to confirm the progress of release etching for forming a MEMS structure that proceeds at the same time. In addition, when the progress of the etching of the monitor sacrificial layer and the progress of the release etching for forming the MEMS structure are not 1: 1, that is, when the etching speed is different, the speed ratio is previously set. By evaluating the above, it is possible to obtain a relatively accurate progress degree of release etching.
As a result, the management of the etching dimensional accuracy for forming the predetermined MEMS structure can be performed more easily and accurately.

(A) The top view which shows the example of the arrangement | positioning state of the process monitor element which concerns on Embodiment 1, (b) Sectional drawing which shows a MEMS element and a process monitor element. (A), (b) The top view and sectional drawing of a process monitor element. (A) Sectional drawing which shows the state which completed release etching, (b) Sectional drawing which shows the completion state in the form of a wafer substrate. (A)-(f) Process drawing which shows the manufacturing method of the MEMS element using the process monitor element which concerns on Embodiment 1. FIG. (G)-(j) Process drawing which shows the manufacturing method of the MEMS element using the process monitor element which concerns on Embodiment 1. FIG. (A), (b) The top view and sectional drawing of the process monitor element which concern on Embodiment 2. FIG. (A), (b) Sectional drawing which shows the process monitor element concerning the modifications 1 and 2. FIG. (A), (b) The top view and sectional drawing which show the process monitor element concerning the modification 3. (A) The top view which shows the process monitor element which concerns on the modification 4, (b) The top view and sectional drawing of the beam sticking monitor with which a process monitor element is provided.

  DESCRIPTION OF EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings. The following is one embodiment of the present invention and does not limit the present invention. In the following drawings, the scale may be different from the actual scale for easy understanding.

(Embodiment 1)
First, the process monitor element according to the first embodiment will be described.
FIG. 1A is a plan view showing an example of an arrangement state of MEMS elements and process monitor elements formed on the main surface of the wafer substrate according to the first embodiment.
In FIG. 1A, the MEMS elements 2 are arranged vertically and horizontally on the main surface of the wafer substrate 1, and the process monitor elements 100 are distributed between the MEMS elements 2 on the main surface of the same wafer substrate 1. . The layout in which the process monitor elements 100 are distributed and the number of the process monitor elements 100 are not limited to this, and in-plane variations in the wafer substrate 1 of the process for manufacturing the MEMS element 2 are taken into consideration. It is preferable to set appropriately.

FIG. 1B is a cross-sectional view showing the MEMS element 2 and the process monitor element 100. This figure is a cross-sectional view of a portion of the arrangement such as part A in FIG. 1A, for example, a cross-section before the MEMS structure of the MEMS element 2 is formed, that is, before the sacrificial layer is release-etched. The figure is shown. A MEMS vibrator 3 is shown as an example of the MEMS structure.
The wafer substrate 1 is a silicon substrate, and the MEMS vibrator 3 is formed on the first oxide film 13 and the nitride film 14 stacked on the wafer substrate 1.
Here, the direction in which the first oxide film 13 and the nitride film 14 are sequentially laminated on the main surface of the wafer substrate 1 is described as an upward direction.

  The MEMS vibrator 3 includes a lower electrode 11 and an upper electrode 12 having a movable part. The lower electrode 11 and the upper electrode 12 are preferably made of conductive polysilicon. Between the lower electrode 11 and the upper electrode 12, a second dioxide film 15 is formed. A third oxide film 16 and a fourth oxide film 17 are stacked on the MEMS vibrator 3. The 2nd-4th oxide films 15-17 are sacrificial layers for forming a MEMS structure, and the MEMS structure which has a movable part is formed by removing these by release etching. Specifically, by removing the second to fourth oxide films 15 to 17, a movable electrode structure having a cantilever structure in which the upper electrode 12 is separated from the lower electrode 11 is formed.

The sacrificial layer formed of the third oxide film 16 and the fourth oxide film 17 has a wall portion 20 provided around the MEMS element 2 or the process monitor element 100 disposed adjacent to the sacrificial layer. doing.
The wall portion 20 includes a semiconductor layer 21b that forms the upper electrode 12, a first wiring layer 22, a second wiring layer 23, and the like. As described above, the semiconductor layer 21b is made of conductive polysilicon as a preferred example, and the first wiring layer 22 and the second wiring layer 23 are made of aluminum as a preferred example. Note that the wiring material is not limited to these, and materials used in the semiconductor process can be utilized.
The second wiring layer 23 constituting the uppermost portion of the wall portion 20 is formed so as to cover the fourth oxide film 17 constituting the sacrificial layer in the MEMS element 2. The second wiring layer 23 is provided with a plurality of release holes 24 for introducing an etchant for release etching the sacrificial layer, and the fourth oxide film 17 is exposed in the release holes 24.
A fifth oxide film 25 as a protective film is laminated on the upper portion of the wall portion 20.

The electrical wiring layer that electrically connects the lower electrode 11 or the upper electrode 12 and the external electrical circuit is formed by the semiconductor layer 21b, the first wiring layer 22, the second wiring layer 23, and the like. Omitted. Further, the external electric circuit can be configured integrally with the MEMS element 2 as a semiconductor circuit. That is, the first to fifth oxide films 13, 15 to 17, 25 as well as the semiconductor layer 21b constituting the upper electrode 12 are used as insulating films such as an interlayer film and a protective film, as well as the first wiring layer 22 and the second wiring layer 22. The wiring layer 23 can be made of a material for integrally forming a semiconductor circuit as a circuit wiring layer. In other words, the MEMS element 2 can be formed in a semiconductor circuit manufacturing process.
In particular, in the case of a MEMS vibrator having a movable electrode formed of a semiconductor, it can be easily incorporated into a semiconductor process as compared with a vibrator such as a crystal.

  The process monitor element 100 is a process monitor element in the process of manufacturing the MEMS element 2 and includes a monitor sacrificial layer 30, a resist layer 31, an etching hole 32, a gauge 40, and the like. In particular, the process monitor element 100 can monitor the progress of the etching in the release etching process of the sacrificial layer in the production of the MEMS element 2.

The monitor sacrificial layer 30 includes the third oxide film 16 and the fourth oxide film 17. Since the process monitor element 100 does not have the MEMS vibrator 3, the monitor sacrificial layer 30 is laminated on the nitride film 14.
Similar to the sacrificial layer of the MEMS element 2 formed of the third oxide film 16 and the fourth oxide film 17, the monitor sacrificial layer 30 is provided around the periphery so as to separate the adjacent MEMS element 2. Wall 20.
The configuration of the wall portion 20 is the same as that of the MEMS element 2 except for the pattern formed by the second wiring layer 23 constituting the uppermost portion. In the case of the MEMS element 2, the second wiring layer 23 is formed so as to cover the fourth oxide film 17 constituting the sacrifice layer in the MEMS element 2, but in the process monitor element 100, the monitor sacrifice layer 30 is covered. Absent. Further, a gauge 40 is formed by patterning with the second wiring layer 23 at the uppermost portion of the wall portion 20. The gauge 40 will be described later.

A fifth oxide film 25 as a protective film is laminated on the upper portion of the wall portion 20 so as to be continuous with the fifth oxide film 25 of the MEMS element 2 disposed adjacent thereto.
A resist layer 31 is laminated on the monitor sacrificial layer 30 and the fifth oxide film 25. The resist layer 31 is provided with an etching hole 32 for introducing an etchant for etching the monitor sacrificial layer 30, and the monitor sacrificial layer 30 (fourth oxide film 17) is exposed in the etching hole 32. . The etching hole 32 is formed at substantially the center of the monitor sacrificial layer 30 when the monitor sacrificial layer 30 is viewed in plan. Further, the fifth oxide film 25 and the resist layer 31 are transparent, and have a structure in which the lower layer can be visually recognized through. Therefore, when the wafer substrate 1 is viewed in plan, the gauge 40 disposed under the fifth oxide film 25 and the resist layer 31 can be visually recognized.
As shown in FIG. 1B, the resist layer 31 is stacked over the region of the MEMS element 2, but is stacked in the region of the second wiring layer 23 in which the release hole 24 is provided. Not.

In the state shown in FIG. 1B described above, release etching of the sacrificial layer is performed. Specifically, the MEMS vibrator 3 as a MEMS structure is formed by exposing the wafer substrate 1 to an etching solution and performing release etching of the second to fourth oxide films 15 to 17 as sacrificial layers. At the same time, in the process monitor element 100, the monitor sacrificial layer 30 is etched through the etching hole 32.
As an etching solution, buffered hydrofluoric acid is used as a preferred example. Since the etching rate by the buffered hydrofluoric acid with respect to the wall part 20 is extremely smaller than the etching rates with respect to the third oxide film 16 and the fourth oxide film 17 constituting the sacrificial layer, the wall part 20 functions as an etching stopper.

  In this state, the degree of progress of release etching of the second to fourth oxide films 15 to 17 in the region of the MEMS element 2 is formed so that the second wiring layer 23 covers the fourth oxide film 17. It cannot be easily seen. On the other hand, in the process monitor element 100, since the resist layer 31 is transparent, it can be visually observed that the monitor sacrificial layer 30 is etched through the etching hole 32.

FIG. 2A is a plan view of the process monitor element 100 viewed from the direction in which the wafer substrate 1 is viewed in plan, and FIG. 2B is a cross-sectional view taken along the line BB in FIG. In FIG. 2 (a), the second wiring layer 23 including the gauge 40 is located below the resist layer 31 and the fifth oxide film 25, but is visible through the line and is a solid line for easy understanding. Is shown.
2A and 2B, the monitor sacrificial layer 30 shows a state in which etching has progressed with an etching hole 32 as a center.
With reference to FIG. 2 (a), (b), the gauge 40 is demonstrated below.

The gauge 40 is a gauge having a graduation in which the position of the etched interface 30a of the etched monitor sacrificial layer 30 can be viewed relative to the main surface side of the wafer substrate 1, and as shown in FIG. A scale pattern having L is formed. FIG. 2A shows a state in which the maximum width (diameter Wx or Wy) of the etching interface 30a spreading in a circle reaches about 5L.
The wall portion 20 is formed in a rectangular frame shape on the outer peripheral portion of the process monitor element 100, and the gauge 40 is formed by the second wiring layer 23 in the uppermost layer of the wall portion 20. Further, the wall portion 20 and the gauge 40 are formed at positions sufficiently away from the etching hole 32. Specifically, the gauge 40 has the etching interface 30a at the gauge 40 even when release etching is performed for a predetermined release etching time (for example, the maximum allowable etching time) in forming the MEMS structure (MEMS vibrator 3). It is formed at a position where it does not travel to the region.

Note that the scale pattern of the gauge 40 is not limited to the pattern shown in FIG. 2A, and may be any pattern that can quantitatively visually recognize the position of the etching interface 30 a indicating the degree of progress of etching. The gauge 40 may be, for example, a pattern that can be compared with an allowable upper limit and a lower limit, that is, a so-called comparator, even if the gauge 40 cannot be visually recognized quantitatively.
The wall 20 and the gauge 40 have been described as being formed in a rectangular frame shape on the outer periphery of the process monitor element 100. However, as described above, if the wall 20 and the gauge 40 are formed at positions sufficiently away from the etching hole 32, as shown in FIG. For example, it may be formed in a circular frame shape.

FIG. 3A is a cross-sectional view showing a state where release etching is completed.
The sacrificial layer in the region of the MEMS element 2 is provided with a plurality of release holes 24 for introducing an etching solution, so that all the sacrificial layers are removed, whereas the monitor sacrificial layer 30 of the process monitor element 100 is It shows a state where the etching interface 30a is left in a state where the etching is stopped to some extent and the progress of the etching is visible.
The number of release holes 24 and the sizes of the release holes 24 and the etching holes 32 are related to the degree of progress of release etching of the sacrificial layer in the region of the MEMS element 2 and the degree of etching of the monitor sacrificial layer 30 in the process monitor element 100. In other words, it is preferable to set appropriately considering the relationship with the position of the etching interface 30a that can be monitored by visual recognition.

FIG. 3B is a cross-sectional view showing a completed state in the form of the wafer substrate 1.
After the release etching is finished, the sealing layer 50 is laminated after the resist layer 31 is peeled off and washed. Although aluminum is used for the sealing layer 50 as a suitable example, it is not limited to this, and other metal layers may be used.
The release layer 24 is sealed in the region of the MEMS element 2 by the sealing layer 50, and the space where the sacrifice layer is removed by release etching is maintained in a sealed state.
Further, the remaining monitor sacrificial layer 30 is covered with the sealing layer 50 in the region of the process monitor element 100. The surface of the sealing layer 50 in the region of the process monitor element 100 is formed to reflect the unevenness of the remaining monitor sacrificial layer 30 as shown in FIG. Can be visually recognized.

Next, a method for manufacturing a MEMS element using the process monitor element according to the first embodiment will be described.
4A to 4F and FIGS. 5G to 5J are process diagrams sequentially illustrating a method for manufacturing the MEMS element 2 using the process monitor element 100. FIG.

FIG. 4A: A wafer substrate 1 is prepared, and a first oxide film 13 is laminated on the main surface. As a preferred example, the first oxide film 13 is formed of a LOCOS (Local Oxidation of Silicon) oxide film, which is a general element isolation layer in a semiconductor process. However, depending on the generation of the semiconductor process, for example, STI (Shallow Trench Isolation) is used. ) Oxide film may be used.
Next, a nitride film 14 is laminated. The nitride film 14 is resistant to buffered hydrofluoric acid as an etchant and functions as an etching stopper.
Next, the semiconductor layer 21 a is stacked on the nitride film 14. The semiconductor layer 21a is a polysilicon layer that constitutes the lower electrode 11, and is ion-implanted after stacking to give predetermined conductivity.

  FIG. 4B: The semiconductor layer 21 a is patterned by photolithography to form the lower electrode 11, and then thermally oxidized to form the second dioxide film 15. Formation of the oxide film by thermal oxidation is selectively performed on the polysilicon layer. This first dioxide film 15 forms a gap with the upper electrode 12 as a sacrificial layer.

  FIG. 4C: the semiconductor layer 21b is stacked. The semiconductor layer 21 b is a polysilicon layer constituting the lowermost layer of the upper electrode 12 and the wall portion 20. The semiconductor layer 21b is patterned by photolithography to form the lowermost layer of the upper electrode 12 and the wall portion 20. The semiconductor layer 21b constituting the upper electrode 12 is ion-implanted after stacking to have a predetermined conductivity.

  FIG. 4D: the third oxide film 16 constituting the sacrificial layer (including the monitor sacrificial layer 30) is stacked. In the semiconductor process, the third oxide film 16 is formed as an interlayer film (IMD (Inter Metal Dielectric)), and is planarized using TEOS (Tetraethoxysilane) as a suitable example. Depending on the generation of the semiconductor process, planarization by CMP (Chemical Mechanical Polishing) or the like may be performed.

FIG. 4E: Before the first wiring layer 22 is stacked, an exposed portion (hole) for electrically connecting the first wiring layer 22 and the semiconductor layer 21b is formed in the third oxide film 16 by photolithography. To do. Next, the first wiring layer 22 is laminated and patterned by photolithography. As a suitable example, aluminum is laminated on the first wiring layer 22 by sputtering.
In FIG. 4E, since the illustration of the electric circuit is omitted, the first wiring layer 22 is shown only in the second layer portion constituting the wall portion 20.

FIG. 4F: The fourth oxide film 17 is stacked as the second layer constituting the sacrificial layer (including the monitor sacrificial layer 30). In the semiconductor process, the fourth oxide film 17 is formed as an interlayer film (ILD (Inter Layer Dielectrics)), and is planarized using TEOS as a preferred example. Depending on the generation of the semiconductor process, planarization by CMP or the like may be performed.
Next, prior to the lamination of the second wiring layer 23, an exposed portion (hole) for electrically connecting the first wiring layer 22 and the second wiring layer 23 is formed in the fourth oxide film 17 by photolithography. . Next, the second wiring layer 23 is laminated and patterned by photolithography. The second wiring layer 23 constitutes the uppermost layer of the wall 20 and includes a release hole 24 for release etching the sacrificial layer of the MEMS element 2 and covers the sacrificial layer (fourth oxide film 17). In the process monitor element 100, the gauge 40 is formed by patterning.
Note that aluminum is laminated on the second wiring layer 23 as a preferred example by sputtering.

FIG. 5G: A fifth oxide film 25 as a protective film is laminated, and an opening is provided so that the portions where the release hole 24 and the monitor sacrificial layer 30 are etched are exposed and patterned by photolithography. The fifth oxide film 25 may be a protective film common in a semiconductor process (for example, a SiO ₂ film or a SiN two-layer film), and may be a polyimide film or the like.

FIG. 5H: A resist layer 31 is stacked and patterned by photolithography so that an opening where the release hole 24 is exposed and an etching hole 32 are formed.
In this state, a process monitor element 100 for monitoring the progress of etching in the release etching process is prepared.

  FIG. 5 (i): The MEMS vibrator 3 as a MEMS structure is formed by exposing the wafer substrate 1 to an etching solution and performing release etching of the second to fourth oxide films 15 to 17 as sacrificial layers. At the same time, in the process monitor element 100, the monitor sacrificial layer 30 is etched through the etching hole 32. The progress of etching is confirmed by viewing the position of the etching interface 30a and the gauge 40 from the main surface side of the wafer substrate 1 relative to each other. The process proceeds according to the result of the confirmation. For example, if it is determined that release etching is insufficient, release etching is further performed.

FIG. 5 (j): After the release etching is completed, the resist layer 31 is peeled off and washed, and then the sealing layer 50 is stacked and patterned by photolithography so that the MEMS element 2 and the process monitor element 100 are sealed. Although aluminum is used for the sealing layer 50 as a suitable example, it is not limited to this, and other metal layers may be used.
The release layer 24 is sealed in the region of the MEMS element 2 by the sealing layer 50, and the space where the sacrifice layer is removed by release etching is maintained in a sealed state.

As described above, according to the process monitor element and the MEMS element manufacturing method of the present embodiment, the following effects can be obtained.
Since the gauge 40 is provided so that the position of the etched interface 30a of the etched monitor sacrificial layer 30 can be viewed from the main surface side of the wafer substrate 1, the degree of release etching for forming the MEMS vibrator 3 is visually confirmed. be able to.
More specifically, an etching hole 32 for introducing an etching solution is provided in the resist layer 31 laminated on the monitor sacrificial layer 30 (that is, the process monitor element 100 is prepared), and a release for forming the MEMS vibrator 3 is provided. Simultaneously with the etching, the monitor sacrificial layer 30 is etched by the etching solution introduced from the etching hole 32. The degree of progress of the etching of the monitor sacrificial layer 30 based on the exposed portion of the etching hole 32 is visually recognized as an etching interface 30a of the monitor sacrificial layer 30 that passes through the resist layer 31 and gradually spreads in accordance with the etching time. Can do. By comparing the position of the etching interface 30a with a gauge 40 provided in the process monitor element 100, it is possible to check the progress of release etching for forming the MEMS vibrator 3 that has progressed simultaneously. In addition, when the progress of the etching of the monitor sacrificial layer 30 and the progress of the release etching for forming the MEMS vibrator 3 are not 1: 1, that is, when the respective etching speeds are different, By evaluating the speed ratio, it is possible to obtain a relatively accurate progress degree of release etching with respect to the MEMS vibrator 3.
As a result, the etching dimensional accuracy for forming the predetermined MEMS vibrator 3 can be managed more easily and accurately.

  Further, since the gauge 40 is formed at the outer peripheral portion of the region of the monitor sacrificial layer 30 that is etched at least within a predetermined time by the etching solution, that is, at a position not included in the region to be etched, the gauge 40 is predetermined. In this time, it is not affected by etching. Therefore, in the method in which the release etching for forming the MEMS vibrator 3 is sufficiently completed within a predetermined time, the gauge 40 is not affected by the etching, and thus the progress of the release etching can be visually confirmed stably. Can do. Further, since the gauge 40 is not affected by etching, it does not cause particles or the like.

  Moreover, since the gauge 40 is a scale pattern formed in the process of patterning the second wiring layer 23 as an electric wiring layer included in the MEMS element 2, a process for forming a new scale pattern as the gauge 40. There is no need to provide. For example, when the second wiring layer 23 of the MEMS element 2 is formed with a metal pattern by photolithography, a scale with the metal pattern is simultaneously formed, so that the process can be simplified.

  The monitor sacrificial layer 30 has a wall portion 20 provided on the monitor sacrificial layer 30 so as to separate the adjacent MEMS element 2 on the main surface of the wafer substrate 1. The etching rate by the etchant is made of a material smaller than the etching rate for the third oxide film 16 and the fourth oxide film 17 constituting the sacrificial layer. Therefore, for example, even when the etching is performed for a predetermined time or longer, the progress of the etching at the wall portion 20 is suppressed, so that the influence on the adjacent MEMS element 2 can be reduced. . Specifically, when the wall portion 20 is configured as an etching stopper, even if the etching exceeds a predetermined time, the adjacent MEMS element 2 beyond the wall portion 20 is affected by etching. Therefore, the influence of the process monitor element 100 on the adjacent MEMS element 2 can be suppressed.

  In addition, the wall 20 provided in the monitor sacrificial layer 30 is formed in the same configuration as the wall 20 provided in the sacrificial layer for forming the MEMS vibrator 3 by release etching. There is no need to provide a process for forming the wall portion 20 of the process monitor element 100.

  Further, the remaining monitor sacrificial layer 30 is covered with the sealing layer 50 in the region of the process monitor element 100. Since the surface of the sealing layer 50 in the region of the process monitor element 100 is formed reflecting the unevenness of the remaining monitor sacrificial layer 30, the position of the etching interface 30a can be visually recognized as unevenness. That is, not only immediately after the release etching step but also after the MEMS element 2 is completed, by confirming the process monitor element 100 manufactured on the same wafer substrate 1, the release etching of the corresponding MEMS element 2 can be performed. The state can be estimated.

  In the above description, the gauge 40 is described as being formed by patterning using the second wiring layer 23, but it is not always necessary to form the gauge 40 in the second wiring layer 23. For example, the fifth oxide film 25 as a protective film may be graduated by half-etching or the like, or may be a method in which a polyimide layer is laminated on the fifth oxide film 25 and the scale is patterned. good. Further, when the monitor sacrificial layer 30 can be permeated sufficiently, it may be formed by patterning with the lower first wiring layer 22 or the semiconductor layers 21a and 21b.

(Embodiment 2)
Next, the process monitor element according to the second embodiment will be described. In the description, the same components as those in the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.
6A is a plan view showing the process monitor element 101 according to the second embodiment, and FIG. 6B is a cross-sectional view taken along the line CC in FIG. 6A.
In the first embodiment, as shown in FIGS. 2A and 2B, the wall 20 and the gauge 40 are formed at positions sufficiently away from the etching hole 32, and the etching hole 32 is formed in the monitor sacrificial layer 30. Is described as being formed at substantially the center of the monitor sacrificial layer 30 in a plan view, but is not limited to this configuration. As shown in FIG. 6B, when the wall portion 20a close to the etching hole 32 functions sufficiently as an etching stopper and it is considered that the adjacent MEMS element 2 is not affected by etching, the etching hole 32 is set to the wall. It is not necessary to form it in the position away from the part 20a.

The process monitor element 101 includes a wall portion 20v formed in a rectangular frame shape in plan view. The wall portion 20v includes two intersecting wall portions 20a and two wall portions facing and intersecting the wall portion 20a. 20b.
The wall part 20b is the same structure as the wall part 20, and is equipped with the gauge 40 in the uppermost layer.
The wall portion 20 a does not include the gauge 40 on the uppermost layer, and therefore, there is no portion where the fifth oxide film 25 covering the gauge 40 is laminated on the monitor sacrificial layer 30. Therefore, even when excessive etching is performed, the MEMS element 2 adjacent through the fifth oxide film 25 is not affected by etching, and the wall portion 20a functions sufficiently as an etching stopper. Therefore, the etching hole 32 can be formed in the vicinity of the corner of the wall portion 20a on the two intersecting sides, and the state in which the etching progresses around the etching hole 32, that is, the position of the etching interface 30a is determined by the wall portion 20b. Relative viewing can be performed by the gauge 40 provided. In other configurations, the process monitor element 101 is the same as the process monitor element 100.

As described above, according to the process monitor element 101 according to the second embodiment, in addition to the effects of the first embodiment, the following effects can be obtained.
Since it is not necessary to form the etching holes 32 at positions away from all the surrounding wall portions 20, the process monitor element can be made smaller. As a result, the area occupied by the process monitor elements disposed on the wafer substrate 1 can be reduced, so that more MEMS elements can be formed.

  Note that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be added to the above-described embodiment. A modification will be described below. Here, the same components as those in the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

(Modification 1)
FIG. 7A is a cross-sectional view showing a process monitor element 102 according to the first modification.
The process monitor element 102 is formed by laminating a region of the monitor sacrificial layer 30 that is etched within at least a predetermined time by an etching solution on a conductive layer that is electrically connected to an electric wiring layer included in the adjacent MEMS element 2. It is characterized by being. The configuration of the process monitor element 102 will be specifically described below.

First, as shown in FIG. 7A, after the first oxide film 13 and the nitride film 14 are laminated on the wafer substrate 1, the monitor sacrificial layer 30 (the third oxide film 16 and the fourth oxide film 17) is laminated. Before, the conductive layer 51 is laminated. The conductive layer 51 is formed by patterning the semiconductor layer 21b (or the semiconductor layer 21a). The range in which the conductive layer 51 is stacked is separated from the adjacent MEMS element 2 by the range where the monitor sacrificial layer 30 is etched by the etchant at least within a predetermined time and the underlying layer of the monitor sacrificial layer 30 is exposed. What is necessary is just a continuous range including the range in which the wall part 20 is formed.
Further, the first wiring layer 22 constituting the wall portion 20 that separates the adjacent MEMS element 2 is patterned to be electrically connected to the electric wiring layer provided in the adjacent MEMS element 2.

  Next, after the release etching is completed, the resist layer 31 is peeled off and washed in the same manner as the process monitor element 100, and the sealing layer 50 is laminated. A part of the sealing layer 50 is laminated on the portion of the base layer exposed by etching the monitor sacrificial layer 30. That is, a part of the metal layer constituting the sealing layer 50 is laminated on the conductive layer 51 as a base layer, and the conductive layer 51 is electrically connected to the electric wiring layer provided in the adjacent MEMS element 2. Since the first wiring layer 22 is formed, the sealing layer 50 is electrically connected to the electric wiring layer provided in the adjacent MEMS element 2. Next, the sealing layer 50 is patterned by photolithography, and a boundary region (in the plan view, around the process monitor element 102 so as to be separated from the sealing layer 50 stacked on the adjacent MEMS element 2). The sealing layer 50 in a region surrounding the sealing layer 50 is removed, and a portion of the sealing layer 50 stacked on the process monitor element 102 is formed as the electrode pad 55.

  According to this modification, by forming the electrode pad 55 as described above, the sealing layer 50 can be configured as an electrode pad portion that is electrically connected to the electric wiring layer included in the MEMS element 2. . In other words, the electrode pad portion to be included in the MEMS element 2 can be configured and used as a process monitor element having the functions and effects of the above-described embodiment in the manufacturing process.

(Modification 2)
FIG. 7B is a cross-sectional view showing a process monitor element 103 according to the second modification.
The process monitor element 103 is formed by laminating an area of the monitor sacrificial layer 30 that is etched within at least a predetermined time by an etching solution on an insulating layer that is laminated on a conductive layer that can be electrically connected to an external electric circuit. It is characterized by having. The configuration of the process monitor element 103 will be specifically described below.

The process monitor element 103 includes a process monitor unit 103a and an additional electrode unit 103b.
The process monitor unit 103 a has the same configuration as the process monitor element 100 except that the conductive layer 52 is provided below the first oxide film 13.
The additional electrode portion 103b is a portion which is adjacent to the process monitor portion 103a and forms an electrode pad 56 for electrically connecting the conductive layer 52 and an external electric circuit.

  First, as shown in FIG. 7B, a conductive layer 52 is formed on the main surface of the wafer substrate 1 before the first oxide film 13 and the nitride film 14 are stacked. The conductive layer 52 is formed in a predetermined region of the main surface of the wafer substrate 1 by diffusing an impurity (dopant) doped in the semiconductor. The predetermined region where the conductive layer 52 is formed is a range that overlaps a range where the monitor sacrificial layer 30 is etched by the etchant at least within a predetermined time and the underlying layer of the monitor sacrificial layer 30 is exposed when viewed in plan. And a continuous region including a range overlapping the electrode pad 56 included in the additional electrode portion 103b.

The additional electrode portion 103b repeats patterning by photolithography, and the first wiring layer 22 between the conductive layer 52 and the sealing layer 50 stacked in the opening of the protective film (the fifth oxide film 25), and The second wiring layer 23 and the like are electrically connected, and the sealing layer 50 stacked on the additional electrode portion 103 b is patterned so as to be independent as the electrode pad 56.
Further, the sealing layer 50 stacked on the process monitor unit 103a is patterned by photolithography, and the boundary region (when viewed in plan view) is separated from the sealing layer 50 stacked on the adjacent MEMS element 2 In addition, the sealing layer 50 in a region surrounding the periphery of the process monitor element 103 is removed, and a portion of the sealing layer 50 stacked on the process monitor unit 103 a is formed as the electrode pad 55.

  According to this modification, the region of the monitor sacrificial layer 30 etched at least within a predetermined time is laminated on the conductive layer 52 that can be electrically connected to the external electric circuit via the electrode pad 56 ( The first oxide film 13 and the nitride film 14) are stacked. Therefore, as shown in FIG. 7B, after performing the etching process, the resist layer 31 is peeled off, and the sealing layer 50 (metal pattern) including the region of the etched monitor sacrificial layer 30 is laminated, By forming the electrode pad 55 and the additional electrode portion 103b, a capacitor structure (capacitor) 53 having an insulating layer between the electrode pad 55 and the conductive layer 52 can be formed. In other words, the portion where the capacitor 53 is formed can be configured and used as the process monitor element described above in the manufacturing process.

(Modification 3)
FIG. 8A is a plan view showing a process monitor element 104 according to Modification 3, and FIG. 8B is a cross-sectional view taken along the line BB.
The process monitor element 104 is characterized in that a conductive member constituting the wall portion 20 forms a surrounding coil structure so as to circulate around the monitor sacrificial layer 30. The configuration of the process monitor element 104 will be specifically described below.

  As described above, the wall portion 20 is made of a conductive material such as the semiconductor layer 21b, the first wiring layer 22, and the second wiring layer 23. As shown by a broken line arrow in FIG. In this case, the process monitor element 104 is continuously formed so as to go around the outer periphery of the rectangular frame shape. However, one corner portion has an insulating portion 60 that is electrically insulated. That is, at one corner portion, the wall portion 20 is cut, and the two end portions (C1, C2) separated by cutting are insulated by the insulating portion 60. The insulating part 60 is formed by the third oxide film 16, the fourth oxide film 17 and the fifth oxide film 25. One end portion C1 of the wall portion 20 that abuts the insulating portion 60 is electrically connected to a terminal that can be electrically connected to an external electric circuit, and the other end portion C2 of the wall portion 20 that abuts the insulating portion 60. Is electrically connected to the conductive layer 57 on which the region of the monitor sacrificial layer 30 to be etched by the etchant at least within a predetermined time is stacked.

More specifically, first, as shown in FIG. 8B, the first oxide film 13 and the nitride film 14 are laminated on the main surface of the wafer substrate 1, and then the conductive layer 57 is formed. The conductive layer 57 is formed by patterning the semiconductor layer 21b stacked on the nitride film 14 by photolithography and leaving it in a predetermined region portion. The predetermined region where the conductive layer 57 is formed is a region that overlaps a range where the monitor sacrificial layer 30 is etched by the etchant at least within a predetermined time and the underlying layer of the monitor sacrificial layer 30 is exposed when viewed in plan. This is a region 57b that connects the region 57a and the first wiring layer 22 that constitutes the other end C2 of the wall portion 20).
The first wiring layer 22 (or the second wiring layer 23) is patterned so that one end C1 of the wall 20 is electrically connected to a terminal that can be electrically connected to an external electric circuit (FIG. 8). (A)). Connection to an external circuit may be performed by connecting to an electrode pad provided for connection as in the additional electrode portion 103b.
Further, the sealing layer 50 laminated on the process monitor element 104 is formed as an electrode pad 55 as in the above-described modification.

  According to this modification, the wall portion 20 is configured to include a conductive material, and includes an insulating portion 60 that is electrically insulated in a part surrounding the monitor sacrificial layer 30 when the wafer substrate 1 is viewed in plan. The monitor sacrificial layer 30 is continuously formed so as to surround it. One end portion C1 of the wall portion 20 that abuts the insulating portion 60 is electrically connected to a terminal that can be electrically connected to an external electric circuit, and the other end portion C2 of the wall portion 20 that abuts the insulating portion 60. Is electrically connected to the conductive layer 57 in which the region of the monitor sacrificial layer 30 to be etched at least within a predetermined time by the etching solution is laminated. Therefore, after the etching process, the resist layer 31 is peeled off, and the sealing layer 50 (metal pattern) including the etched region of the monitor sacrificial layer 30 is laminated to remain unetched. A coil structure that wraps around the monitor sacrificial layer 30 can be formed. In other words, the part forming the coil structure can be configured and used as the process monitor element described above in the manufacturing process.

(Modification 4)
FIG. 9A is a plan view showing a process monitor element 105 according to the fourth modification.
The process monitor element 105 is characterized in that a beam sticking monitor 70 is formed in the region of the monitor sacrificial layer 30 that is etched by an etchant at least within a predetermined time. The process monitor element 105 is the same as the process monitor element 100 except that a beam sticking monitor 70 is provided. The configuration of the process monitor element 105 will be specifically described below.

FIG. 9B is a plan view and a cross-sectional view of the beam sticking monitor 70 provided in the process monitor element 105.
The beam sticking monitor 70 is a process monitor structure for evaluating sticking composed of a plurality of cantilevered beams 71 having different lengths released by etching as shown in FIG. 9B. . Sticking is a phenomenon in which a fine structure such as a beam adheres to a substrate or another structure when the sacrificial layer is removed by etching. The beam sticking monitor 70 forms a structure of a lower electrode and an upper electrode by the semiconductor layer 21 a and the semiconductor layer 21 b stacked on the nitride film 14 in the same manner as the MEMS vibrator 3. The upper electrode is composed of a beam 71 having a cantilever structure having a plurality of different lengths in order to evaluate sticking. The dimension specifications of the plurality of beams 71 are appropriately set depending on the evaluation contents. Since the beam 71 having a cantilever structure is actually release-etched, it is preferable to consider so that the beam 71 is broken as a fragment in a cleaning process or the like and does not become particles.

According to this modification, for example, the MEMS element 2 includes a cantilever beam having the same configuration as the cantilever beam 71 formed in the process monitor element 105 as the MEMS vibrator 3. In FIG. 5, the progress of the etching of the monitor sacrificial layer 30 and the progress of the release etching for forming the MEMS vibrator 3 can be more approximated. Therefore, it is possible to manage the etching dimensional accuracy with higher accuracy.
In addition, by forming a plurality of cantilevered beams 71 having different lengths, it is possible to perform cleaning subsequent to release etching, evaluation of beam sticking in a drying process, and the like. In other words, the portion for evaluating the sticking of the beam can be configured and used as the process monitor element described above in the manufacturing process.

  DESCRIPTION OF SYMBOLS 1 ... Wafer substrate, 2 ... MEMS element, 3 ... MEMS vibrator, 11 ... Lower electrode, 12 ... Upper electrode, 13 ... 1st oxide film, 15-17 ... 2nd acid-4th oxide film, 14 ... Nitride film 20 ... walls, 21a, 21b ... semiconductor layer, 22 ... first wiring layer, 23 ... second wiring layer, 24 ... release hole, 25 ... fifth oxide film, 30 ... monitor sacrificial layer, 30a ... etching interface, DESCRIPTION OF SYMBOLS 31 ... Resist layer, 32 ... Etching hole, 40 ... Gauge, 50 ... Sealing layer, 51, 52, 57 ... Conductive layer, 53 ... Capacitor, 55, 56 ... Electrode pad, 60 ... Insulating part, 70 ... Beam sticking monitor , 100 to 105, process monitor elements, 103a, process monitor units, 103b, additional electrode units.

Claims (11)

A process monitor element in a MEMS element manufacturing process for forming a plurality of MEMS elements having a MEMS structure formed by etching a sacrificial layer on a main surface of a wafer substrate,
Disposed on the main surface of the wafer substrate;
Said sacrificial layer comprising a monitor sacrificial layer;
A resist layer laminated on the monitor sacrificial layer;
An etching hole formed in the resist layer and exposing the monitor sacrificial layer;
A process monitor element, comprising: a gauge capable of viewing the position of the etching interface of the monitor sacrificial layer etched by the etchant introduced from the etching hole relative to the main surface side of the wafer substrate.   The process monitor element according to claim 1, wherein the gauge is formed on an outer peripheral portion of the region of the monitor sacrificial layer that is etched by the etchant at least within a predetermined time.   The process monitor element according to claim 1, wherein the gauge is a scale pattern formed in a step of patterning an electric wiring layer included in the MEMS element.   3. The process monitor element according to claim 1, wherein the gauge is a scale pattern formed in a step of patterning a base layer forming the MEMS structure. 4. The monitor sacrificial layer has a wall portion provided in the monitor sacrificial layer so as to separate the adjacent MEMS element on the main surface of the wafer substrate,
5. The process monitor element according to claim 1, wherein an etching rate of the etching solution with respect to the wall portion is smaller than an etching rate of the etching solution with respect to the sacrificial layer.   The wall portion provided in the monitor sacrificial layer is formed in the same configuration as a wall portion provided in the sacrificial layer for forming the MEMS structure by release etching. 5. The process monitor element according to 5.   The region of the monitor sacrificial layer etched at least within a predetermined time by the etchant is formed by being laminated on a conductive layer electrically connected to an electric wiring layer included in the MEMS element. The process monitor element according to any one of claims 1 to 6.   The region of the monitor sacrificial layer etched at least within a predetermined time by the etchant is formed by being stacked on an insulating layer stacked on a conductive layer that can be electrically connected to an external electric circuit. The process monitor element according to any one of claims 1 to 6. The wall portion is configured to include a conductive material, and when the wafer substrate is viewed in plan, the wall portion includes an insulating portion that is electrically insulated in a portion surrounding the monitor sacrificial layer so as to surround the monitor sacrificial layer. Formed continuously,
One end of the wall portion in contact with the insulating portion is electrically connected to a terminal that can be electrically connected to an external electric circuit;
The other end of the wall portion in contact with the insulating portion is electrically connected to a conductive layer on which the region of the monitor sacrificial layer etched by the etchant at least within a predetermined time is stacked. The process monitor element according to claim 5, wherein:   A plurality of cantilever beam beams having different lengths released by the etching are formed in the region of the monitor sacrificial layer etched by the etchant at least within a predetermined time. The process monitor element according to any one of claims 1 to 6. Forming a process monitor element according to any one of claims 1 to 10,
Etching the sacrificial layer, including the monitor sacrificial layer;
A step of confirming a release range of the MEMS structure by viewing a position of an etching interface formed by etching the monitor sacrificial layer relative to the gauge, and manufacturing a MEMS element Method.

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