JP2008309657A - Structure manufactured from laminate and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for materializing a structure which has stoppers for preventing contact between a base layer and an active layer for forming a weight section, and has increased the mass of the weight section. <P>SOLUTION: This manufacturing method is provided with an anisotropic etching process for performing anisotropic etching of the active layer and exposing a sacrificial layer, and an isotropic etching process for performing isotropic etching of the sacrificial layer from the exposed range and isolating the active layer for forming beams and the weight section from the base layer. A group of isolated ranges are formed while being scattered having relations satisfying equation (1) x<10.0, and equation (2) 1.0<G<h+1.0 simultaneously, when the minimum diameter of individual isolated ranges to be etched by the anisotropic etching process is represented by x(μm), the shortest one among the distances from the center point of a region whose perimeter is surrounded by isolated ranges up to the isolated ranges is represented by G(μm), and the thickness of the sacrificial layer is represented by h(μm). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a structure manufactured by etching a predetermined range of a sacrificial layer and an active layer from a stacked body in which a base layer, a sacrificial layer, and an active layer are stacked in this order. The present invention also relates to a method for manufacturing the structure.

Patent Document 1 discloses a technique for manufacturing a structure including a base, a beam, and a weight from a stacked body in which a base layer, a sacrificial layer, and an active layer are stacked in this order. The base is formed by an active layer in a range fixed to the base layer via a sacrificial layer. The beam is formed by an active layer that extends from the active layer that forms the base and is free from the base layer because the corresponding sacrificial layer is etched. The weight portion is formed by an active layer in a range free from the base layer because the sacrificial layer in a corresponding range is etched and the sacrificial layer in a corresponding range is etched.
Such a structure includes a fixed electrode that faces the weight portion and is fixed to the base layer. A capacitor is formed by applying a voltage between the weight portion and the fixed electrode. By detecting a change in the capacitance of the capacitor, it can be used as a mechanical quantity detection device such as an acceleration detection device or an angular velocity detection device. Alternatively, it can be used as an actuator by changing the voltage applied to the fixed electrode. Patent Document 1 discloses an example in which the structure is used as an acceleration detection device. An example in which the above structure is used as an angular velocity detection device is disclosed in Patent Document 2.
In the conventional structure manufacturing method, first, the active layer in the range excluding the connection part of the base and the beam, the connection part of the beam and the weight part in the range along the outer periphery of the beam and the weight part, The sacrificial layer is exposed by anisotropically etching the active layers in a plurality of isolated ranges that are dispersed in the substrate. At this stage, a plurality of through holes penetrating from the front surface to the back surface of the active layer are formed in the active layer forming the weight portion. Next, the sacrificial layer is isotropically etched from the exposed range in the through hole, and the active layer forming the beam and the weight portion is released from the base layer.

JP 2000-150917 A JP 2001-330442 A

  In the manufacturing method of Patent Document 1, in the step of anisotropically etching the active layer, it takes a longer time than the etching time (etching time until the sacrificial layer is exposed) required to form a through hole in the active layer. (Excessively) anisotropic etching is performed. When the anisotropic etching is excessive, notching occurs in the active layer at the boundary between the active layer and the sacrificial layer. The notching here refers to a phenomenon in which the cross-sectional area of the through hole is enlarged near the bottom surface of the through hole. When notching occurs, an etchant used for isotropic etching easily enters between the active layer and the sacrificial layer when the isotropic etching is performed, and the sacrificial layer can be quickly removed. However, if the active layer is etched excessively, notching occurs not only in the through hole in the weight portion but also in the active layer that defines the contour of the weight portion and the active layer that forms the beam. When notching occurs in the contours of the weight part and the beam, their shapes deviate from the set values, and a phenomenon such as variation in the resonance frequency occurs, resulting in a decrease in detection accuracy of the detection device. In addition, when the structure is used as an actuator, problems such as unstable operation of the base and the beam occur. In order to bring the characteristics of the structure close to the design value, it is not preferable to generate notching in the entire range of the active layer. In addition, Patent Document 2 has a description that notching should be prevented from occurring in the active layer in order to maintain good detection accuracy of the angular velocity detection device.

For example, when an acceleration detection device or an angular velocity detection device is manufactured using the above structure, the detection sensitivity improves as the mass of the weight portion increases. Therefore, it is preferable to reduce the volume occupied by the through-hole formed in the active layer for the weight portion. That is, it is preferable to increase the interval between adjacent through holes or reduce the minimum diameter of the through holes. Even if the interval between adjacent through holes is increased or the minimum diameter of the through holes is reduced, the weight portion and the beam portion can be released from the base layer by setting the isotropic etching time longer. However, in the above structure, a sacrificial layer in a range where the through hole and the through hole are separated is used as a stopper for preventing the active layer forming the weight portion and the base layer from contacting (sticking). It is preferable to leave it. In order to ensure that the stopper remains, the sacrificial layer exposed from the through hole is etched in the isotropic etching process, and the etching must be stopped when the base layer is exposed. That is, if the time of isotropic etching is increased in response to increasing the interval between adjacent through holes or reducing the minimum diameter of the through holes, the active layer forming the base layer and the weight portion Can be released, but the stopper does not remain.
The present invention provides a technique for realizing a structure that includes a stopper for preventing contact between the active layer forming the weight portion and the base layer and in which the mass of the weight portion is increased.

According to the research of the present inventor, when the active layer is anisotropically etched, if the width of less than 10.0 μm is anisotropically etched, the boundary portion between the active layer and the sacrificial layer can be obtained without excessive etching of the active layer. It was found that notching occurred. In the present invention, the structure is manufactured using the technique.
In the structure manufacturing method of the present invention, when anisotropic etching is performed, notching is generated only in the through holes formed in a distributed manner in the weight portion. Notching is not generated in the portion etched to determine the contour of the weight portion or the beam. If notching occurs in the through-holes that are dispersed in the weight part, the area of the sacrificial layer exposed in the through-holes increases, so the distance between adjacent through-holes is increased compared to the case where notching does not occur. Or the minimum diameter of the through hole can be reduced. Since notching is not generated in the active layer that defines the contour of the weight portion, the weight portion does not deviate from the set value, and the weight of the weight portion can be increased.

In the present invention, a base formed by an active layer in a range fixed to the base layer via the sacrificial layer is formed from the stacked body in which the base layer, the sacrificial layer, and the active layer are sequentially stacked, and the base is formed. The beam is formed by the active layer extending from the active layer and being free from the base layer because the corresponding sacrificial layer is etched, and fixed to the opposite base side of the beam And a method of manufacturing a structure comprising a weight portion formed by an active layer in a range free from a base layer because a corresponding range of sacrificial layer is etched.
The manufacturing method includes an active layer in a range excluding a connection portion between the base and the beam, a connection portion between the beam and the weight portion in a range along the outer periphery of the beam and the weight portion, and a dispersion in the weight portion. An anisotropic etching process in which a sacrificial layer is exposed by anisotropically etching a plurality of isolated active layers, and a beam in which the sacrificial layer is isotropically etched from the area exposed in the anisotropic etching process. And an isotropic etching step for releasing the active layer forming the weight portion from the base layer. Here, the minimum diameter of the isolated range is x (μm), the shortest distance from the center point of the region surrounded by the isolated range to the isolated range is G (μm), and the thickness of the sacrificial layer is h ( μm), the isolated range group is formed in a distributed manner so as to satisfy the following expressions (1) and (2) simultaneously.
x <10.0 (1)
1.0 <G <h + 1.0 (2)
In addition, the “minimum diameter” of the isolated range or the through hole in the present specification refers to the minimum diameter of all the diameters measured through the central position of the isolated range or the through hole. That is, when the isolated area or the through hole is rectangular or square, it means the length of the short side, and when the isolated area or the through hole is a circle, it means the diameter.

  According to the above manufacturing method, a plurality of through holes can be dispersed and formed in the weight portion in the anisotropic etching step. Since the above equation (1) is satisfied, even if anisotropic etching is performed so that notching is not formed in the active layer in the range along the outer periphery of the beam and the weight portion, the active layer is dispersedly formed in the weight portion. In the through hole group to be formed, the active layer at the boundary between the active layer and the sacrificial layer can be formed with a notch that is etched by spreading about 1.0 μm toward the outside of the through hole. The minimum diameter of the through hole opened to the base layer side can be increased by about 2.0 μm. Further, since the above formula (2) is satisfied, the active layer and the sacrificial layer forming the beam and the weight portion can be separated, and a stopper is provided between the active layer forming the weight portion and the base layer. Can be formed. That is, a part of the sacrificial layer corresponding to the active layer that separates the through hole and the through hole can be left. Since notching is formed in the through hole group, the minimum diameter of the anisotropic etching range can be made smaller than when notching is not formed, and the mass of the weight portion can be increased. As a result, for example, the detection accuracy of a mechanical quantity detection device manufactured using the structure can be improved.

Here, referring to FIGS. 14 to 18, by satisfying the above equations (1) and (2) at the same time, the active layer and the sacrificial layer forming the beam and the weight portion can be separated, and the weight portion The reason why the stopper can be formed between the active layer and the base layer forming the layer will be described. FIG. 14A shows a case where the isolated area is a circle, FIG. 14B shows a case where the isolated area is a square, and FIG. 14C shows a case where the isolated area is a rectangle.
As described above, in the isotropic etching process, the etching is stopped when the sacrificial layer is etched and the base layer is exposed. That is, only the sacrificial layer corresponding to the distance (sacrificial layer thickness h) between the base layer and the active layer is etched. Therefore, a sacrificial layer in a range not exposed at the bottom of the through hole (a sacrificial layer in a range in which the upper active layer is not etched) is separated from a boundary portion between the exposed sacrificial layer and the unexposed sacrificial layer. A portion existing within a distance corresponding to the thickness h is etched. In the weight portion, the center point M of the region surrounded by the isolated range is most difficult to be etched.

15 to 17 show a process of isotropic etching of the sacrificial layer 24 after forming the through hole 4 by anisotropically etching the isolated region. FIG. 15 shows a case of 2h + 2.0 <2G (that is, h + 1.0 <G). FIG. 16 shows the case of 2h + 2.0 = 2G (that is, h + 1.0 = G). FIG. 17 shows the case of 2h + 2.0> 2G (that is, h + 1.0> G). As is apparent from the drawings, the relationship of 2.0 <2G (that is, 1.0 <G) is satisfied in FIGS. In FIG. 15 to FIG. 17, the dimensional unit is omitted, but the dimensional unit is all μm.
As described above, since the minimum diameter of the isolated region is less than 10.0 μm, the active layer 2 at the boundary between the active layer 2 and the sacrificial layer 24 is etched by spreading about 1.0 μm toward the outside of the through hole 4. The Before the isotropic etching, the sacrificial layer 24 remains up to the line t0. When isotropic etching is started, the sacrificial layer 24 is etched in the order of the line t1, the line t2, and the line t3. The etching is performed up to the line t3, and the isotropic etching is finished when the base layer 6 is exposed. The line t3 shows the outer shape of the sacrificial layer 24 when the sacrificial layer 24 is etched by a distance corresponding to the thickness h of the sacrificial layer 24.
As shown in FIG. 15, when h + 1.0 <G, the sacrificial layer 24 at the center point M of the region surrounded by the isolated range cannot be etched. That is, the active layer 2 cannot be released from the base layer 6.
As shown in FIG. 16, when h + 1.0 = G, isotropic etching (line t3) that has progressed from different through-holes 4 at the center point M occurs when etching is performed by a distance corresponding to the thickness h of the sacrificial layer. Reach.
As shown in FIG. 17, in the case of h + 1.0> G, isotropic etching (line t3) proceeding from different through holes 4 intersects each other when etching is performed by a distance corresponding to the thickness h of the sacrificial layer. That is, the active layer 2 can be released from the base layer 6 at the center point M that is most difficult to be etched. Also, the sacrificial layer 24 can be left as a stopper near the center point M.

FIG. 18 shows a case where 2.0 = 2G (that is, 1.0 = G). At this time, the active layer 2 at the boundary between the active layer 2 and the sacrificial layer 24 is etched by spreading about 1.0 μm toward the outside of the through hole 4, and the etching of the different through holes 4 reaches the center point M. Therefore, the sacrificial layer 24 in contact with the center point M starts to be etched from the time when the isotropic etching is started. As a result, when the sacrificial layer 24 is isotropically etched by the thickness h, the sacrificial layer 24 cannot be left as a stopper.
For the above reasons, by simultaneously satisfying the above expressions (1) and (2), the active layer and the sacrificial layer forming the beam and the weight portion can be separated, and the active layer and the base forming the weight portion are separated. A stopper can be formed between the layers.

When the shape of the isolated range is a circle or a square, the size of the isolated range and the interval between adjacent isolated ranges can be used as parameters. In the manufacturing method, a plurality of isolated ranges each having a circular shape or a square shape are arranged in a lattice shape at equal intervals in the weight portion, and the distance from the center of the isolated range to the farthest end is defined as r (μm). When the interval between the isolated ranges is P (μm), the isolated range groups are formed in a distributed manner so as to satisfy the following formula (3).
2 ^0.5 × (r + 1.0) <P <2 ^0.5 × (r + h + 1.0) (3)
As used herein, the “distance from the center to the farthest end” of the isolated range or through hole means the distance from the center to the apex when the isolated range or through hole is square. When the area or through hole is a circle, it means the radius.

As shown in FIGS. 14A and 14B, when the shape of the isolated area is a circle or square and the isolated areas are arranged in a lattice at equal intervals, the following formula (4) is obtained. .
(2 × G) + (2 × r) = 2 ^0.5 × P (4)
When the formula (4) is transformed, the following formula (5) is obtained.
G = (1/2) * 2 ^0.5 * Pr (5)
Substituting equation (5) into equation (2) yields equation (3) above.
According to the above manufacturing method, when the value of the thickness h of the sacrificial layer is known, the distance between adjacent isolated ranges can be determined by determining the size of the isolated range (distance r from the center C of the isolated range to the farthest end). The possible range of P is determined. On the contrary, if the interval P between adjacent isolated ranges is determined, the range in which the size r of the isolated range can be determined. While satisfying the condition that the active layer and the sacrificial layer that form the beam and the weight portion can be separated and the stopper can be formed between the active layer and the base layer that form the weight portion, The mass can be increased.

Even when a plurality of rectangular isolated ranges are arranged in a lattice pattern at equal intervals, the size of the isolated range and the interval between adjacent isolated ranges can be expressed by the above equation (3). However, a definition specific to the rectangular isolated area is required for the center of the isolated area.
As shown in FIG. 14C, “the center C1 of the rectangular isolated range” refers to the center of a circle inscribed in the three sides described later of the isolated range. The three sides here are the three sides of the two sides a and b that intersect at the vertex P1 closest to the center point M of the region surrounded by the isolated range, and the side c that faces the long side a across the short side b. I mean. The center C1 of the rectangular isolated range is located on a line L1 connecting the center point M and the vertex P1. The distance r from the center of the rectangular isolated range to the farthest end is the distance between the center C1 and the vertex P1.
Note that “arranging rectangular isolated ranges at equal intervals” means that the distance of the range surrounded by the isolated range in the short side direction of the isolated range is s1, and the isolated range is surrounded by the isolated range in the long side direction of the isolated range. When the distance of the range is s2, all the distances s1 are the same distance, all the distances s2 are the same distance, and the distances s1 and s2 are the same distance.

The structure realized by the present invention is a structure manufactured from a laminated body in which a base layer, a sacrificial layer, and an active layer are laminated in this order, and is active in a range fixed to the base layer via the sacrificial layer. The base formed by the layer and the active layer extending from the active layer forming the base and the corresponding active layer in the range free from the base layer because the corresponding sacrificial layer is etched. A weight part formed by an active layer in a range that is fixed to the opposite base side of the beam and is free from the base layer because the corresponding sacrificial layer is etched. A plurality of through-holes penetrating from the front surface to the back surface of the active layer forming the weight portion, and a sacrifice that remains in a range where the plurality of through-holes are separated and is fixed to the base layer layer Therefore and a stopper being formed. The minimum diameter of the through hole is x (μm), the shortest distance from the center point of the region surrounded by the through hole to the through hole is G (μm), and the thickness of the sacrificial layer is h (μm). In such a case, the relationship is set to satisfy the following expressions (1) and (2) simultaneously.
x <10.0 (1)
1.0 <G <h + 1.0 (2)

  According to said structure, it can prevent that the active layer and base layer which form the beam and the weight part contact. In addition, a stopper can be formed between the active layer forming the weight portion and the base layer. The notch is formed in the through hole opened to the base layer side, and the minimum diameter x of the through hole can be made smaller than the case where the notch is not formed. The mass of the active layer that forms the weight portion can be increased.

When the shape of the through hole is circular or square, the dimension of the through hole and the interval between the adjacent through holes can be used as parameters. In the weight portion, a plurality of through holes each having a circular or square shape are formed in a lattice shape at equal intervals in the weight portion, and the distance from the center of the through hole to the farthest end is r (μm), When the interval between adjacent through-holes is P (μm), the through-hole surrounding groups are formed in a distributed manner so as to satisfy the following formula (3).
2 ^0.5 × (r + 1.0) <P <2 ^0.5 × (r + h + 1.0) (3)
When the value of the thickness h of the sacrificial layer is known, the weight portion is adjusted by adjusting the dimension of the through hole (distance r from the center of the through hole to the farthest end) and / or the interval P between adjacent through holes. A structure in which the mass of the active layer to be formed is increased can be designed.

  In the case of a rectangular through hole, the meanings of “the center of the through hole”, “the distance from the center of the through hole to the farthest end”, and “place at equal intervals (formation)” are the same as the meaning of the rectangular isolated range. is there.

The structure of the present invention is preferably a silicon structure. That is, it is preferable that the sacrificial layer is silicon oxide and the active layer is silicon.
In the above silicon structure, a combination etching method can be employed in which the sacrificial layer is not etched when the active layer is anisotropically etched, and the active layer is not etched when the sacrificial layer is isotropically etched.

In the silicon structure of the present invention, x in the above formulas (1) and (2) is preferably larger than 2.0 μm.
When x is 2.0 μm or less, since the minimum diameter of the through hole is too small, it becomes difficult for the etching agent to enter the inside of the through hole. In the isotropic etching, the sacrificial layer is hardly etched, and the active layer and the base layer that form the weight portion are not easily released. By making x larger than 2.0 μm, the etching agent can easily enter the through hole, and the active layer and the base layer that form the weight portion can be surely released.

In the silicon structure of the present invention, it is preferable that at least a part of the contour of the weight portion has a wave shape.
According to the above silicon structure, since the dimple effect is obtained when the weight portion vibrates with respect to the base layer, the air resistance is reduced. For example, when the silicon structure is used for an angular velocity detection device or the like, the air resistance applied to the weight portion can be reduced, and the detection accuracy of the detection device can be increased.

In the silicon structure of the present invention, it is preferable that a space of less than 10.0 μm is formed between the active layer forming the weight portion and the active layer forming the base portion adjacent to the weight portion.
According to the above silicon structure, notching can also be formed in the active part on the outer periphery of the weight part. Since the outer periphery of the weight portion can be expanded outward by the amount of notching, the mass of increased activity forming the weight portion can be increased.

  According to the present invention, in the structure manufactured from the laminate in which the base layer, the sacrificial layer, and the active layer are laminated in order, the stopper for preventing the contact between the active layer forming the weight portion and the base layer is provided. And the mass of the weight portion can be increased.

The main features of the examples are listed.
(Feature 1) A plurality of first flat plate groups are formed on the side wall of the weight portion, and a plurality of second flat plate portion groups are formed on the base portion. The first flat plate group and the second flat plate group are alternately arranged opposite to each other.
(Characteristic 2) Notching is formed in the through-hole opened to the base layer side.
(Characteristic 3) Square isolated ranges are arranged at regular intervals in a grid pattern.

(First embodiment)
In this embodiment, an example in which a silicon structure is applied to an acceleration detection device will be described. FIG. 1 schematically shows a plan view of the acceleration detecting device 100. FIG. 2 is a sectional view taken along the line II-II in FIG. FIG. 3 shows a cross-sectional view taken along line III-III in FIG. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. In the figure, X, Y, and Z indicate coordinate axes. Further, the configuration of each part of the acceleration detection device 100 does not accurately represent the actual size scale. In order to clarify the drawing, the scale of the drawing is appropriately changed.
In the present embodiment, an example in which the through hole 4 is a square is shown. As shown in FIGS. 14A to 14C, the stopper described later is formed at the position of the center point M of the region surrounded by the through hole (isolated range) 4. When the interval P between adjacent through holes is equal, the distance G from the center point M to the through hole 4 can be maximized when the through hole 4 is square. Or the minimum diameter x of the through-hole 4 can be made the smallest. As a result, the weight of the active layer that forms the weight portion can be increased. In addition, although the present Example shows about the example where the through-hole 4 is square, the shape of the through-hole 4 is not limited to a square, and may be a rectangle or a circle.

As shown in FIG. 1, the acceleration detection device 100 includes base portions 14 a to 14 d, beams 12 a to 12 d, and a weight portion 2. A plurality of square through holes 4 are formed in the weight portion 2 in a lattice shape at equal intervals. In the following description, when describing an event common to a plurality of the same type of configuration, alphabetic suffixes may be omitted.
As shown in FIG. 2, the base portion 14 is formed by the active layer 3 in a range fixed to the base layer 6 via the sacrificial layer 24. The beam 12 extends from the active layer 3 forming the base portion 14, and is formed by the active layer 3 in a range free from the base layer 6. The weight portion 2 is fixed to the side opposite to the base portion 14 of the beam 12 and is formed by the active layer 3 in a range free from the base layer 6. In the acceleration detection device 100, the distance between the beam 12, the weight portion 2, and the base layer 6 (that is, the thickness h of the sacrificial layer 24) is 4.5 μm. The base layer 6 and the active layer 3 are made of silicon, and the sacrificial layer 24 is made of silicon oxide. Since the active layer 3 is implanted with impurities, the resistance is kept low.

As shown in FIG. 3, the through hole 4 penetrates from the front surface to the back surface of the active layer forming the weight portion 2. When the length (minimum diameter) of one side of the through hole 4 is x (μm), the minimum diameter x of the through hole satisfies the following formula (1).
x <10.0 (1)
A notching 5 is formed on the side (back side) of the through hole 4 that opens to the base layer 6. The width of the notching is about 1.0 μm. The notch is not formed in the side wall 2S which determines the outline of the weight part 2. Since the notching 5 is formed on the back surface side of the through hole 4, the length of one side opening on the back surface of the through hole 4 is longer than the length x (minimum diameter) of one side opening on the surface of the through hole 4. Is about 2.0 μm larger. In the acceleration detection device 100, the length of one side opened on the surface of the through hole 4 is 8.0 μm, and the length of one side opened on the back surface of the through hole 4 is 10.0 μm.
As shown in FIG. 4, a stopper 26 is fixed to the surface of the base layer 6 in a range where the through hole 4 and the through hole 4 are separated. As will be described later, the stopper 26 is formed by leaving the sacrificial layer in the step of isotropic etching of the sacrificial layer. The distance between the active layer forming the weight portion 2 and the base layer (equal to the thickness of the sacrificial layer 24 in FIG. 2) is h (μm), and from the center point M of the region surrounded by the through hole If the shortest distance to the through hole is G (μm), the distance G satisfies the following formula (2).
1.0 <G <r + 1.0 (2)
Further, when the distance from the center of the through hole 4 to the apex (farthest end) of the through hole 4 is r (μ) and the interval between the adjacent through holes 4 is P (μm), G is the following formula (5) (See also FIG. 14).
G = (1/2) * 2 ^0.5 * Pr (5)
From the above formulas (2) and (5), the interval P between the adjacent through holes 4 can be expressed by the following formula (3).
2 ^0.5 × (r + 1.0) <P <2 ^0.5 × (r + h + 1.0) (3)
That is, the acceleration detecting device 100 satisfies the above expressions (1) and (3) at the same time (in other words, satisfies the above expressions (1) and (2) at the same time). It is formed in a dispersed manner. As described above, the shape of the through hole 4 may be a rectangle or a circle.

As shown in FIG. 1, the beam 12 has a shape in which the distance in the X-axis direction is long and the distance in the Y-axis direction is short, and the beam 12 can be deformed in the Y-axis direction. Further, as described above, the weight portion 2 is formed free from the base layer 6. Therefore, the weight portion 2 can be displaced in the Y-axis direction with respect to the base layer 6.
A plurality of first flat plate groups 8 are formed on a part of the side wall of the weight portion 2. A plurality of second flat plate groups 10 are formed at positions facing the first flat plate group 8. The flat plates of the first flat plate group 8 and the second flat plate group 10 are alternately arranged. The second flat plate group 10 is fixed to the fixing portion 18, and the active layer forming the fixing portion 18 is fixed to the base layer 6 by the sacrificial layer 24. That is, each flat plate of the second flat plate group 10 cannot be displaced with respect to the base layer 6. A capacitor 16 is formed by the first flat plate group 8 and the second flat plate group 10. The capacitors 16a to 16d all have the same configuration. An electrode 22 is formed on the base portion 14c, and electrodes 20a to 20d are formed on the fixing portions 18a to 18d, respectively.

The operation of the acceleration detection device 100 will be described.
In the acceleration detection device 100, a circuit (not shown) for detecting the capacitance of each of the capacitors 16a to 16d is connected between the electrode 22 and the electrodes 18a to 18d. When no force (acceleration) is applied to the acceleration detection device 100, the capacitance of the capacitor 16 is maintained at a predetermined value. When a force around the Z axis is applied to the acceleration detection device 100, the weight part 2 is displaced in the Y axis direction, and the capacitances of the capacitors 16a to 16d change. By detecting changes in the capacitances of the capacitors 16a to 16d, the acceleration applied to the acceleration detecting device 100 can be detected.

A method for manufacturing the acceleration detection device 100 will be described with reference to FIGS. Here, a method of manufacturing a portion corresponding to FIG. 4 will be described.
As shown in FIG. 5, the acceleration detecting device 100 is manufactured from a stacked body 29 in which a base layer 6, a sacrificial layer 24, and an active layer 3 are stacked in this order.
First, as shown in FIG. 6, the sacrificial layer 24 is exposed by anisotropically etching the active layer in a predetermined portion (in the isolated range) of the active layer 3. A through hole 4 is formed in an isolated range of the active layer 3 that forms the weight portion 2. The anisotropic etching is performed by RIE (Reactive Ion Etching) method or the like. The anisotropic etching employs a method in which the active layer (silicon) 3 is etched but the sacrificial layer (silicon oxide) 24 is not etched. When the active layer 3 is anisotropically etched, the notching 5 is formed only in the through hole 4 on the side opening toward the sacrificial layer 24. As described above, the notching 5 is formed by about 1.0 μm toward the outside of the through hole 4.
In addition, as shown in the side wall 2s of the weight part 2 in FIG. 3, even if the active layer 3 is etched, notching is not formed in the part other than the isolated range. The reason why there are portions where the notching 5 is formed in the active layer 3 and portions where the notching is not formed will be described later.

Next, the sacrificial layer 24 is isotropically etched to release the base layer 6 and the weight portion 2. Isotropic etching employs a method in which the sacrificial layer (silicon oxide) 24 is etched but the weight 2 (active layer 3) and the base layer 6 are not etched. For example, wet etching using a hydrogen fluoride (HF) aqueous solution or the like can be given. The isotropic etching proceeds isotropically from the portion where the sacrificial layer 24 is exposed. That is, the etching of the sacrificial layer 24 where the active layer 3 is not etched proceeds from the portion surrounded by the broken line N in the drawing.
The isotropic etching stops when all of the sacrificial layer 24 exposed in the anisotropic etching process is etched and the base layer 6 is exposed. That is, the etching is stopped when the sacrificial layer 24 located in a portion separated from the exposed sacrificial layer 24 by a distance h (thickness of the sacrificial layer 24) is etched. Therefore, only the sacrificial layer 24 existing in the part separated by the distance h from the part surrounded by the broken line N is etched in the part of the sacrificial layer 24 where the active layer 3 is not etched.
Through the above steps, the portion shown in FIG. 4 of the acceleration detecting device 100 is formed. Parts other than those shown in FIG. 4 can be manufactured simultaneously with the parts shown in FIG. Thereafter, the electrode 20 is formed on the fixed portion 18 and the electrode 22 is formed on the base portion 14c, whereby the acceleration detecting device 100 is completed.
Since the acceleration detecting device 100 satisfies the above formula (2) or (3), the base layer 6 and the active layer 3 are released, but one of the sacrificial layers 24 between the base layer 6 and the active layer 3 is released. The portion remains and the stopper 26 (see FIG. 4) is formed. The active layer 3 forming the weight portion 2 can be displaced with respect to the base layer 6 and can be prevented from coming into contact with each other.

Here, it will be described that notching is formed only in the through hole 4 on the side opened to the sacrificial layer 24 and no notching is formed in a portion other than the through hole 4. FIGS. 11 to 13 are formed when the minimum diameter x of the isolated range is changed when anisotropically etching a plurality of isolated ranges of silicon (active layer) stacked on the surface of the silicon oxide (sacrificial layer). 2 shows an SEM (Scanning Electron Microscope) photograph of a through-hole. Here, an example of forming a square through-hole will be described. The anisotropic etching was stopped when the silicon was etched and the silicon oxide was exposed. FIG. 11 shows a through hole when x = 4.0 μm, FIG. 12 shows a through hole when x = 8.0, and FIG. 13 shows a through hole when x = 10.0 μm.
FIG. 11A shows a through hole that opens on the surface side of silicon. FIG.11 (b) has shown the one part enlarged view of Fig.11 (a). FIG. 11C shows a through hole that opens on the back side of silicon (the side in contact with silicon oxide). FIG.11 (d) has shown the one part enlarged view of FIG.11 (c). In addition, the black part of a photograph represents the through-hole formed by etching silicon.
As is clear from FIGS. 11A to 11D, notching is not formed on the surface side of silicon. On the back side of the silicon, notching is confirmed around the through hole. The width of the notching is about 1.0 μm.

FIG. 12A shows a through hole that opens on the surface side of silicon. FIG.12 (b) has shown the one part enlarged view of Fig.12 (a). FIG. 12C shows a through hole opened on the back side of silicon. FIG.12 (d) has shown the one part enlarged view of FIG.12 (c).
As is clear from FIGS. 12A to 12D, notching is not formed on the surface side of silicon. On the back side of the silicon, notching is confirmed around the through hole. The width of the notching is about 1.0 μm.

FIG. 13A shows a through hole that opens on the surface side of silicon. FIG.13 (b) has shown the one part enlarged view of Fig.13 (a). FIG.13 (c) has shown the through-hole opened on the back surface side of a silicon | silicone. FIG.13 (d) has shown the one part enlarged view of FIG.13 (c).
As is clear from FIGS. 13A to 13D, notching is not formed on both the front surface side and the back surface side of silicon. Although detailed data is not shown here, both the front side and the back side of silicon are notched even when the value of the minimum diameter x is larger than 10.0 μm (for example, x = 12.0 μm, x = 16.0 μm). Is not formed.

From the results of FIGS. 11 to 13, when the minimum diameter of the isolated range is made smaller than 10.0 μm, notching is formed in the through hole opened on the back surface side of the silicon. In order to reliably form the notching in the through hole opened on the back surface side of the silicon, it is preferable that the minimum diameter x of the isolated range is larger than 2.0 μm and not larger than 8.0 μm.
As described above, in the acceleration detection device 100, the minimum diameter x of the isolated range is 8.0 μm. For this purpose, notching is formed at a portion of the through hole that opens on the back side of the silicon.

(Second embodiment)
The angular velocity detection device 200 will be described with reference to FIG. The angular velocity detection device 200 is a modification of the acceleration detection device 100, and description thereof may be omitted by giving the same reference numerals to substantially the same configuration as the acceleration detection device 100. Also in the present embodiment, when describing an event common to the same type of configuration in which there are a plurality, the alphabetic suffix may be omitted.
One end of a beam 229 extending in the Y-axis direction from the base 228 is fixed to the frame 230. The weight portion 2 is fixed to one end of a beam 212 extending from the frame 230 in the X-axis direction. The base 228 is formed by an active layer in a range fixed to the base layer 206 through a sacrificial layer. An electrode 222 is formed on the base 228c. The beams 212 and 229, the frame 230, and the weight portion 2 are formed by an active layer in a range free from the base layer 206.
The beam 212 has a shape with a long distance in the X-axis direction and a short distance in the Y-axis direction, and the beam 229 has a shape with a long distance in the Y-axis direction and a short distance in the X-axis direction. Therefore, the weight portion 2 can be displaced in the X-axis direction and the Y-axis direction with respect to the base layer.
A plurality of third flat plate groups 232 are formed on a part of the side wall of the frame 230. A plurality of fourth flat plate groups 234 are formed at positions facing the third flat plate group 232. The flat plates of the third flat plate group 232 and the fourth flat plate group 234 are alternately arranged. The fourth plate group 234 is fixed to the second fixing portion 236, and the second fixing portion 236 is fixed to the base layer 206. That is, each flat plate of the fourth flat plate group 234 cannot be displaced with respect to the base layer 206. A capacitor 240 is formed by the third plate group 232 and the fourth plate group 234. Capacitors 240a to 240d all have the same configuration. Electrodes 238a to 238d are formed on the second fixing portions 236a to 236d, respectively.

The operation of the angular velocity detection device 200 will be described.
In the angular velocity detection device 200, the weight portion 2 is vibrated with respect to the base layer 206 in advance. An alternating voltage V1 having a predetermined frequency is applied to the electrodes 238a and 238b, and an alternating voltage V2 having a predetermined frequency is applied to the electrodes 238c and 238d. Here, a phase difference is provided between the AC voltages V1 and V2. Thereby, charge and discharge of electric charge are repeated in capacitors 240a to 240d. The weight portion 2 vibrates in the X-axis direction due to the electrostatic force of the charges charged and discharged in the capacitors 240a to 240d.
When the angular velocity detection device 200 rotates around the Z axis in a state where the weight portion 2 is vibrating in the X-axis direction, a Coriolis force acts on the weight portion 2. The magnitude and direction of the Coriolis force varies depending on the vibration of the weight portion 2 in the X-axis direction, the rotation speed around the Z-axis, and the rotation direction. When force is applied to the weight portion 2, the weight portion 2 vibrates in the Y-axis direction due to Coriolis force. The displacement amount of the weight portion 2 in the Y-axis direction is an amount corresponding to the force applied to the weight portion 2 and the vibration of the weight portion 2 in the X-axis direction.
When the weight portion 2 vibrates in the Y-axis direction, the capacitance changes in the capacitors 16a to 16d. By detecting changes in the capacitances of the capacitors 16a to 16d, the rotational speed applied to the angular velocity detection device 200 can be detected.

(Third embodiment)
The acceleration detection apparatus 300 will be described with reference to FIGS. The acceleration detection device 300 is a modified example of the acceleration detection device 100, and description thereof is omitted by attaching the same reference numerals to substantially the same components as the acceleration detection device 100. FIG. 8 shows a plan view of the acceleration detection device 300, and FIG. 9 shows a cross-sectional view along the line IX-IX in FIG.
As shown in FIG. 8, a wall 352 connecting the base portion 14a and the base portion 14d and between the base portion 14b and the base portion 14c is formed. The active layer forming the wall 352 is fixed to the base layer 6 via the sacrificial layer 24. A convex portion 352a is formed on the wall 352 at a position facing the side wall 2S of the weight portion 2. The gap between the weight part 2 and the convex part 352a is approximately 4 μm.
As shown in FIG. 9, in the acceleration detection device 300, the notching 5 is also formed on the back surface side of the side wall 2 </ b> S of the weight portion 2. The size of the weight portion 2 can be increased by the length (1 μm) of the notching 5 formed on the back surface side of the side wall 2S. The mass of the weight portion 2 can be increased as compared with the acceleration detection device 100.

(Fourth embodiment)
The angular velocity detection device 400 will be described with reference to FIG. The angular velocity detection device 400 is a modification of the angular velocity detection device 200, and only a configuration different from the angular velocity detection device 200 will be described.
A wave shape 42 is formed on the side wall 2 </ b> S of the weight portion 2. By forming the wave shape 42, when the weight portion 2 vibrates with respect to the base layer 206 (not shown), the air resistance received by the weight portion 2 due to the dimple effect can be reduced. A detection capability with higher accuracy than that of the angular velocity detection device 200 can be realized. Further, in the step of isotropically etching the sacrificial layer 24 (not shown), an effect that the etching agent easily enters from the side wall 2S of the weight portion 2 is also obtained.

Specific examples of the present invention have been described above in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
In the above-described embodiment, an example in which the structure of the present invention is used as an acceleration detection device or an angular velocity detection device has been described. However, the structure of the present invention can also be used as a device for detecting mechanical quantities such as angular acceleration, external force, and pressure.
In the above-described embodiment, an example in which the structure of the present invention is used as a device for detecting a mechanical quantity has been described. However, the structure of the present invention can also be used as an actuator. By changing the capacitance of the capacitor, the active layer forming the weight portion can be displaced with respect to the base layer.
In the third embodiment, an example in which a wall is formed at a position facing the weight portion in the acceleration detection device of the first embodiment has been described. The feature of the third embodiment, that is, the technique of forming a wall at a position facing the weight portion can also be applied to the angular velocity detection device of the second embodiment.
In the fourth embodiment, an example in which a wave shape is formed on the side wall of the wall in the angular velocity detection device of the second embodiment has been described. In the acceleration detecting device of the first embodiment, a wave shape may be formed on the side wall of the wall.
In addition, the technical elements described in the present specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in the present specification or the drawings can achieve a plurality of objects at the same time, and has technical utility by achieving one of the objects.

The top view of the acceleration detection apparatus of 1st Example is shown. Sectional drawing along the II-II line | wire of FIG. 1 is shown. Sectional drawing along the III-III line | wire of FIG. 1 is shown. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 1. The manufacturing process of the acceleration detection apparatus of 1st Example is shown. The manufacturing process of the acceleration detection apparatus of 1st Example is shown. The top view of the angular velocity detection apparatus of 2nd Example is shown. The top view of the acceleration detection apparatus of 3rd Example is shown. FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8. A part of top view of the acceleration detection apparatus of 4th Example is shown. The SEM photograph in case the minimum diameter of the through-hole formed in the weight part is 4 micrometers is shown. The SEM photograph in case the minimum diameter of the through-hole formed in the weight part is 8 micrometers is shown. The SEM photograph in case the minimum diameter of the through-hole formed in the weight part is 10 micrometers is shown. Indicates the location and dimensions of the isolated area. The process of isotropic etching of the sacrificial layer is shown. The process of isotropic etching of the sacrificial layer is shown. The process of isotropic etching of the sacrificial layer is shown. The process of isotropic etching of the sacrificial layer is shown.

Explanation of symbols

2: Weight part 3: Active layer 4: Through hole 5: Notching 6, 206: Base layers 12a to 12d: Beams 14a to 14d: Base parts 16a to 16d: Capacitor 24: Sacrificial layer 26: Stoppers 228a to 228d: Base part 240a to 240d: Capacitor

Claims (8)

A base formed by an active layer in a range in which a base layer, a sacrificial layer, and an active layer are stacked in that order and fixed to the base layer via the sacrificial layer, and an activity forming the base A beam formed by the active layer extending from the layer and being free from the base layer because the corresponding sacrificial layer is etched, and fixed to the opposite base side of the beam A method of manufacturing a structure comprising a weight portion formed by a range of active layers free from a base layer because a corresponding range of sacrificial layers has been etched, comprising:
Of the range along the outer periphery of the beam and the weight portion, the active layer in the range excluding the connection portion between the base portion and the beam, and the connection portion between the beam and the weight portion, and a plurality of dispersedly arranged in the weight portion An anisotropic etching step of exposing the sacrificial layer by anisotropically etching the active layer in the isolated range;
Comprising an isotropic etching step in which the active layer forming the beam and the weight portion is released from the base layer by isotropically etching the sacrificial layer from the range exposed in the anisotropic etching step,
The minimum diameter of the isolated range is x (μm), the shortest distance from the center point of the region surrounded by the isolated range to the isolated range is G (μm), and the thickness of the sacrificial layer is h (μm). In the manufacturing method, the isolated range group is formed in a distributed manner so as to satisfy the following expressions (1) and (2) simultaneously.
x <10.0 (1)
1.0 <G <h + 1.0 (2) In the weight part, each of a plurality of isolated ranges of circular or square is arranged in a lattice at equal intervals,
When the distance from the center of the isolated range to the farthest end is r (μm) and the interval between adjacent isolated ranges is P (μm), the isolated range group is dispersed in a relationship satisfying the following expression (3). The manufacturing method according to claim 1, wherein:
2 ^0.5 × (r + 1.0) <P <2 ^0.5 × (r + h + 1.0) (3) A structure manufactured from a laminate in which a base layer, a sacrificial layer, and an active layer are laminated in order,
A base formed by an active layer in a range fixed to the base layer via a sacrificial layer;
A beam formed by the active layer extending from the active layer forming its base and free from the base layer because the corresponding sacrificial layer is etched;
A weight portion formed by an active layer in a range that is fixed to the opposite base side of the beam and is free from the base layer because the corresponding sacrificial layer is etched,
A plurality of through holes penetrating from the front surface to the back surface of the active layer forming the weight portion;
A stopper formed by a sacrificial layer that remains in a range separating the plurality of through holes and is fixed to the base layer;
The minimum diameter of the through hole is x (μm), the shortest distance from the center point of the region surrounded by the through hole to the through hole is G (μm), and the thickness of the sacrificial layer is h (μm). And a structure that is set in a relationship that satisfies the following expressions (1) and (2) at the same time.
x <10.0 (1)
1.0 <G <h + 1.0 (2) In the weight portion, a plurality of circular or square through holes are formed in a lattice shape at equal intervals,
When the distance from the center of the through-hole to the farthest end is r (μm) and the interval between adjacent through-holes is P (μm), the through-hole surrounding group is dispersed so as to satisfy the following formula (3). The structure according to claim 3, wherein the structure is formed.
2 ^0.5 × (r + 1.0) <P <2 ^0.5 × (r + h + 1.0) (3)   5. The silicon structure according to claim 3, wherein the sacrificial layer is silicon oxide and the active layer is silicon.   6. The silicon structure according to claim 5, wherein x is larger than 2.0 [mu] m.   7. The silicon structure according to claim 5, wherein at least a part of the contour of the weight portion has a wave shape.   8. The space of less than 10.0 μm is formed between the active layer forming the weight portion and the active layer forming the base portion adjacent to the weight portion. Any silicon structure.