Crack prevention structure of laminated film and semiconductor device including crack prevention structure of laminated film

Abstract

To provide a structure in which tensile stress is hardly concentrated and which is hardly broken in a laminated film.SOLUTION: The crack prevention structure of the laminated film has a substrate 11 and a single crystal layer 12 laminated on the main surface of the substrate 11 and made of a material different from that of the substrate 11. When the single-crystal layer 12 is viewed from the normal direction of the main surface of the substrate 11, the curvature radius of the concave portion at a point of contact S between a perpendicular line D1 of a cleavage surface direction D2 of the single-crystal layer 12 and the concave portion of the single-crystal layer 12 is set to a predetermined value or more. The length L3, which is the curvature radius of the concave portion, is longer than the length D2, which is the maximum length of the single-crystal layer 12 in the perpendicular line L1 passing through the tangent point S.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] SUMMARY OF THE DISCLOSURE Embodiments of the present disclosure relate to a structure for preventing cracks in a laminated film and a semiconductor device including the structure for preventing cracks in a laminated film. [Background technology]

[0002] Conventionally, MEMS (Micro Electro Mechanical Systems) devices, also known as microelectromechanical systems, have been used in a variety of applications. MEMS devices are devices that use microfabrication technology to form tiny three-dimensional structures on a single substrate, integrating mechanical components, electronic circuits, sensors, actuators, and other elements, and are constructed by layering functional materials such as piezoelectrics on structures such as silicon (Si) substrates.

[0003] Examples of applications of MEMS devices in the high-frequency field include high-frequency switches or filters, oscillators, and resonators. In resonators and filters, good crystallinity of the constituent laminated films is one of the important factors in reducing parasitic resistance and achieving a high Q value. On the other hand, aluminum nitride, a piezoelectric material, has a high Q value and is therefore used in FBAR (Film Bulk Acoustic Resonator) high-frequency filters for mobile communications. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-51000

[0005] [overview] However, during the process of stacking each layer, compressive or tensile stress is applied to each layer due to the difference in the lattice constant of the crystal of each layer. Depending on the strength of the stress or external stimuli, cracks may occur in the layer to which tensile stress is applied, resulting in a problem of reduced manufacturing yield and device performance.

[0006] An object of the present disclosure is to provide a structure in which tensile stress is less likely to concentrate and cracks are less likely to occur in a laminated film.

[0007] A crack prevention structure for a laminated film according to one embodiment of the present disclosure includes a substrate and a single-crystal layer made of a material different from that of the substrate, laminated on a main surface of the substrate, wherein, when the single-crystal layer is viewed from the normal direction of the main surface of the substrate, a curvature radius of a recess at a point where the recess contacts a perpendicular to the cleavage plane direction of the single-crystal layer is set to a predetermined value or greater. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view of a semiconductor device according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the semiconductor device according to the first embodiment. [Figure 3] FIG. 3 is a plan view of the semiconductor device according to the first embodiment, with electrodes removed. [Figure 4] FIG. 4 is a plan view illustrating the crack prevention structure of the semiconductor device according to the first embodiment. [Figure 5A] FIG. 5A is a cross-sectional view showing tensile stress and compressive stress in a laminated film of a substrate and a single crystal layer. [Figure 5B] FIG. 5B is a cross-sectional view showing tensile stress and compressive stress in a laminated film of a substrate and a single-crystal layer. [Figure 6A] FIG. 6A is a plan view showing the shape of a single crystal layer in a laminated film, the direction of a cleavage plane, and the direction of tensile stress. [Figure 6B] FIG. 6B is a plan view showing the shape of the single crystal layer in the laminated film, the direction of the cleavage plane, and the direction of the tensile stress. [Figure 6C] FIG. 6C is a plan view showing the shape of the single crystal layer in the laminated film, the direction of the cleavage plane, and the direction of the tensile stress. [Figure 7] FIG. 7 is an enlarged plan view of a part of FIG. [Figure 8A]FIG. 8A is a diagram showing the crystal orientation of a single crystal silicon wafer in which the (111) plane is exposed. [Figure 8B] FIG. 8B is a diagram showing the cleavage plane direction and the direction of the concave curve of the semiconductor device according to the first embodiment. [Figure 9] FIG. 9 is a plan view of a connection portion between a resonance plate and an anchor in a semiconductor device of a comparative example. [Figure 10] FIG. 10 is an enlarged plan view of a connection portion between a resonance plate and an anchor in a semiconductor device of a comparative example. [Figure 11] FIG. 11 is a plan view illustrating the crack prevention structure for a semiconductor device according to the second embodiment. [Figure 12] FIG. 12 is an enlarged plan view of a part of FIG. [Figure 13] FIG. 13 is an enlarged plan view of the crack prevention structure for a semiconductor device according to the third embodiment. [Figure 14] FIG. 14 is a cross-sectional view of a crack prevention structure for a semiconductor device according to the third embodiment. [Figure 15] FIG. 15 is an enlarged plan view of a case where a crack occurs in the crack prevention structure of the semiconductor device according to the third embodiment. [Figure 16] FIG. 16 is an enlarged plan view of the crack prevention structure for a semiconductor device according to the fourth embodiment. [Figure 17] FIG. 17 is a cross-sectional view of a crack prevention structure for a semiconductor device according to the fourth embodiment. [Figure 18] FIG. 18 is an enlarged plan view of a case where a crack occurs in the crack prevention structure of the semiconductor device according to the fourth embodiment. [Figure 19] FIG. 19 is an enlarged plan view of the crack prevention structure for a semiconductor device according to the fifth embodiment. [Figure 20] FIG. 20 is an enlarged plan view of a case where a crack occurs in the crack prevention structure of the semiconductor device according to the fifth embodiment.

[0009] [Detailed explanation] The embodiments will be described with reference to the drawings. In the following description of the drawings, the same or similar parts will be denoted by the same or similar reference numerals, and the description thereof will be omitted. The drawings are schematic.

[0010] Furthermore, the embodiments shown below are merely examples of devices and methods for embodying the technical ideas, and do not specify the materials, shapes, structures, arrangements, etc. of each component part. Various modifications can be made to these embodiments within the scope of the claims.

[0011] [First embodiment] (Configuration of semiconductor devices) Fig. 1 is a plan view of a semiconductor device 1 according to a first embodiment. The semiconductor device 1 in Fig. 1 is a resonator. Fig. 2 is a cross-sectional view of the semiconductor device 1 according to the first embodiment taken along line II-II.

[0012] In the following description, an XYZ coordinate system, which is an example of a Cartesian coordinate system, is used. That is, a plane parallel to the main surface of the substrate 11 constituting the semiconductor device 1 is defined as the XY plane, and a normal direction perpendicular to the XY plane is defined as the Z direction. The X axis and Y axis are defined as two orthogonal directions in the XY plane.

[0013] The semiconductor device 1 includes a substrate 11, a single-crystal layer 12 stacked on a major surface of the substrate 11, and electrodes 13a and 13b disposed on the major surface of the single-crystal layer 12. The substrate 11 is, for example, a single-crystal silicon substrate with a (111) plane exposed. The single-crystal layer 12 is made of a different material from the substrate 11, for example, single-crystal aluminum nitride AlN, which is a piezoelectric material. The single-crystal layer 12 is disposed inside the outer edge of the substrate 11 when viewed from the Z direction so that it can be deposited on the substrate 11 even if there is misalignment during manufacturing. Similarly, the electrodes 13a and 13b are disposed inside the outer edge of the single-crystal layer 12 when viewed from the Z direction so that it can be deposited on the single-crystal layer 12 even if there is misalignment during manufacturing. Note that a buffer layer may be inserted between the substrate 11, which is, for example, a single-crystal silicon substrate, and the single-crystal layer 12, which is, for example, single-crystal aluminum nitride AlN, but this is omitted here.

[0014] The semiconductor device 1 includes a rectangular resonator plate 1a. The longitudinal direction of the resonator plate 1a is the Y direction. A cavity 14 is provided around the resonator plate 1a along the outer periphery of the resonator plate 1a. The resonator plate 1a is connected to the area of ​​the semiconductor device 1 outside the cavity 14 at the center of the resonator plate 1a in the X direction by anchor 1b, which is located on the positive side of the Y direction center of the resonator plate 1a, and anchor 1c, which is located on the negative side of the Y direction center. Here, the upper side of the Y direction center in the drawing is referred to as the "positive side," and the lower side is referred to as the "negative side" (the same applies hereinafter). The cavity 14 is provided to penetrate the substrate 11, the single-crystal layer 12, and the electrodes 13a and 13b in the Z direction.

[0015] Electrodes 13a and 13b are arranged on the resonance plate 1a, separated by the center of the resonance plate 1a in the X direction. With the center of the resonance plate 1a in the X direction as a reference, electrode 13a is arranged on the negative side, and electrode 13b is arranged on the positive side. Here, the right side of the center in the X direction in the drawing is referred to as the "positive side," and the left side is referred to as the "negative side" (the same applies below). Electrode 13a extends to an area outside of cavity 14 via anchor 1b. Electrode 13a is separated in two directions and extends to encompass the periphery of cavity 14. Electrode 13b extends to an area outside cavity 14 toward the negative side in the Y direction relative to the resonance plate 1a via anchor 1c. The electrode 13a separated in two directions is extended toward the center in the X direction along the gap 14 on the negative side of the resonance plate 1a in the Y direction, then changes direction to be parallel to the electrode 13b extended toward the negative side of the resonance plate 1a in the Y direction, and is extended toward the negative side of the resonance plate 1a in the Y direction.

[0016] Region 1d, which includes the portion of resonance plate 1a on the negative side relative to the center in the Y direction, anchor 1c, and part of cavity 14, is a region that includes the crack prevention structure of the present disclosure. Region 1d will be described later with reference to FIGS. 3 and 4.

[0017] The semiconductor device 1 is a resonator having a TPOS (thin film piezoelectric on silicon) structure, and mainly utilizes resonance in a contour-type vibration mode in which the substrate 11 included in the resonator plate 1a vibrates laterally. The thickness of the substrate 11 included in the resonator plate 1a and anchors 1b and 1c may be made thinner than the thickness of the substrate 11 outside the gap 14 by, for example, etching the surface of the substrate 11 opposite to the main surface on which the single crystal layer 12 is laminated.

[0018] Figure 3 is a plan view of the semiconductor device 1 of Figure 1, excluding electrodes 13a and 13b. The same parts as in Figure 1 are given the same reference numerals and their explanations will be omitted. The semiconductor device 1 includes a laminated film of a substrate 11 and a single crystal layer 12.

[0019] Fig. 4 is a plan view illustrating the crack prevention structure of the semiconductor device 1 of Fig. 3. Fig. 4 shows an enlarged view of a region 1d in Fig. 3 that includes the connection between the resonator plate 1a and the anchor 1c and part of the gap 14.

[0020] Cracks are likely to occur in the cleavage plane direction D1 in the single crystal layer 12. A perpendicular line D2 perpendicularly intersecting the cleavage plane direction D1 makes contact at a contact point S with a recess on the positive side of the X-axis of the single crystal layer 12 at the portion where the resonator plate 1a of the semiconductor device 1 is connected to the anchor 1c.

[0021] Here, the mechanism by which cracks occur in the single crystal layer 12 in a laminated film of the substrate 11 and the single crystal layer 12 will be described using an example in which the substrate 11 is single crystal silicon (111) and the single crystal layer 12 is single crystal aluminum nitride AlN. Figures 5A and 5B are cross-sectional views showing tensile stress and compressive stress in a laminated film in which the single crystal layer 12 is laminated on the main surface of the substrate 11. Figure 5A is a cross-sectional view before cracks occur in the single crystal layer 12, and Figure 5B is a cross-sectional view after cracks occur in the single crystal layer 12.

[0022] In Figure 5A, since the lattice constant of single-crystal aluminum nitride AlN is smaller than that of single-crystal silicon (111), single-crystal layer 12 is subjected to tensile stress indicated by the arrows from substrate 11, and the portion of substrate 11 that is bonded to single-crystal layer 12 is subjected to compressive stress indicated by the arrows from single-crystal layer 12. The tensile stress that single-crystal layer 12 is subjected to from substrate 11 increases as the length of single-crystal layer 12 to be deposited increases. When single-crystal layer 12 can no longer withstand the tensile stress applied by substrate 11, it cracks and breaks, for example, at the center in the X direction, as shown in Figure 5B.

[0023] When the single crystal layer 12 cracks as shown in FIG. 5B, the length of the single crystal layer 12 in the X direction is shortened, and the tensile stress received from the substrate 11 is alleviated.

[0024] 6A, 6B, and 6C are plan views showing the shape of the single crystal layer 12, the direction of the cleavage plane, and the direction of the tensile stress when the laminated film of the substrate 11 and the single crystal layer 12 is viewed from the Z direction. For ease of explanation, the single crystal layer 12 has the cleavage plane direction in the Y direction, and tensile stress is applied in the X direction perpendicular to the cleavage plane direction. When tensile stress is applied in the direction perpendicular to the cleavage plane direction, cracks are most likely to occur.

[0025] The single-crystal layer 12 of the laminated film shown in Fig. 6A has a triangular recess with a vertex in the Y direction at the center in the X direction. The recess in Fig. 6A is susceptible to cracks occurring at the cleavage plane passing through the vertex of the triangular recess because tensile stress is locally concentrated at the vertex of the triangular recess, making the layer susceptible to breakage.

[0026] The single-crystal layer 12 of the laminated film shown in Fig. 6B has an arc-shaped recess that is convex in the Y direction at the center in the X direction. Compared to the shape of Fig. 6A, the recess in Fig. 6B suppresses the concentration of tensile stress and can withstand a larger tensile stress, but cracks may start near the tip of the recess.

[0027] The single-crystal layer 12 of the laminated film shown in Fig. 6C does not have a recess at the center in the X direction. The shape of Fig. 6C does not allow tensile stress to be concentrated, so cracks are less likely to occur and break.

[0028] Returning to the explanation of Figure 4, perpendicular line D2 and the edge of single-crystal layer 12 of resonance plate 1a on the positive side of the X axis intersect at point B1, and the distance between point B1 and tangent point S is distance L1. Furthermore, perpendicular line D2 and the edge of single-crystal layer 12 of anchor 1c on the negative side of the X axis intersect at point B2, and the distance between point B2 and tangent point S is distance L2. The tensile stress applied to single-crystal layer 12 at tangent point S depends on the length of single-crystal layer 12 in the direction of perpendicular line D2; the longer the single-crystal layer 12 in the direction of perpendicular line D2, the greater the tensile stress. Because distance L1 is longer than distance L2, single-crystal layer 12 is subjected to tensile stress at tangent point S based on distance L1.

[0029] To prevent cracks from occurring in the single-crystalline layer 12 due to tensile stress at the contact point S, the recess in the single-crystalline layer 12 at the connection point between the resonator 1a and the anchor 1c of the semiconductor device 1 is shaped to have a radius of curvature set to a predetermined value or greater, as follows: The shape of the recess on the positive side of the X-axis of the single-crystalline layer 12 at the connection point between the resonator 1a and the anchor 1c is defined by an arc of a circle whose radius is a distance L3, which is longer than the distance L1. Specifically, a line in the cleavage plane direction D1 is extended through the contact point S in the positive direction of the X-axis and the negative direction of the Y-axis, and the position on the extended line that is the distance L3 from the contact point S is defined as position B3. The shape of the recess on the positive side of the X-axis of the single-crystalline layer 12 is defined by an arc C1 of a circle whose radius is the distance L3 from position B3. In other words, the predetermined value of the radius of curvature of the recess is the distance L3, which is longer than the distance L1.

[0030] 7 is an enlarged plan view of region 1d1 of the crack prevention structure of FIG. 4. The recess in the single-crystal layer 12 includes a recess curve E1 defined by an arc C1 of a circle having a radius of a distance L3 longer than the distance L1. The recess curve E1 is perpendicular to the cleavage plane direction D1 at the contact point S, and has a shape that does not concentrate stress even at points moved along the arc C1. In the crack prevention structure of the semiconductor device 1 according to the first embodiment, since stress does not concentrate in the recess, cracks are unlikely to occur in the cleavage plane direction D1 and the single-crystal layer 12 is unlikely to break even when tensile stress is generated in the direction of the perpendicular line D2.

[0031] 7, the cross section of the recess in single crystal layer 12 viewed from a direction parallel to the XY plane forms a curved surface defined by a set of lines connecting in the Z direction recess curve E1 on the main surface of single crystal layer 12 and a projection line of recess curve E1 projected from the Z direction onto the bottom surface of single crystal layer 12. In the XY plane cut from single crystal layer 12 at an arbitrary height, recess curve E1 is defined by the projection from the Z direction of arc C1 of a circle having a radius of distance L3 longer than distance L1.

[0032] 8A is a diagram showing the crystal orientation in which cracks are likely to occur in a single crystal silicon wafer with the (111) plane exposed (hereinafter referred to as a "single crystal silicon (111) wafer"). The substrate 11 of the semiconductor device 1 according to the first embodiment is cut out from the single crystal silicon (111) wafer of FIG. 8A, for example. FIG. 8B is a diagram showing the cleavage plane directions D1 and DL and the directions of the recess curves E1 and EL of the semiconductor device 1 according to the first embodiment.

[0033] 8A, the main surface faces the Z direction, and the orientation flat faces the negative direction of the Y axis. The cleavage planes of single crystal silicon include the (-110) plane, which is indicated by a line parallel to the Y direction, the (-101) plane, which is obtained by rotating the (-110) line 60 degrees to the left around the center of the single crystal silicon (111) wafer, and the (0-11) plane, which is obtained by rotating the (-110) line 60 degrees to the right.

[0034] The single-crystal layer 12 formed on the main surface of the substrate 11 cut from a single-crystal silicon (111) wafer inherits the crystal structure of the single-crystal silicon (111), and therefore is prone to cracking in the same direction as the cleavage plane of the single-crystal silicon (111). That is, the single-crystal layer 12 formed on the main surface of the substrate 11 is prone to cracking along the (-101), (-110), and (0-11) planes.

[0035] 4 and 7, the recess in single-crystal layer 12 at the connection between resonator plate 1a and anchor 1c of semiconductor device 1 is also shown in Fig. 8B, with cleavage plane direction D1 being the direction of the (-101) plane in Fig. 8A. Recess curve E1 is perpendicular to the direction of the (-101) plane at contact point S, and stress is not concentrated at points moved along recess curve E1. Therefore, single-crystal layer 12 of the crack prevention structure of semiconductor device 1 is less likely to crack in the direction of the (-101) plane and is less likely to break.

[0036] Similarly, as shown in Figure 8B, the recess curve EL of the recess on the negative side of the X axis of single-crystal layer 12 at the portion where resonator plate 1a and anchor 1c are connected is set so that it is perpendicular to cleavage plane direction DL at the contact point SL with the recess. The cleavage plane direction DL is the direction of the (0-11) plane in Figure 8A. Since recess curve EL is perpendicular to the direction of the (0-11) plane at the contact point SL and the structure does not cause stress concentration even at points moved along recess curve EL, single-crystal layer 12 of the crack prevention structure of semiconductor device 1 is less likely to crack in the direction of the (0-11) plane and is less likely to break.

[0037] Although detailed explanation is omitted, a shape in which stress is concentrated in the cleavage plane direction (hereinafter referred to as "cleavage plane direction DV"), which is the direction of the (-110) plane in Figure 8A, can be made less likely to crack in the (-110) plane direction and less likely to break by similarly widening the part perpendicular to the (-110) plane direction to prevent stress concentration.

[0038] Here, to facilitate understanding of the features of the present disclosure, a semiconductor device of a comparative example will be described.

[0039] 9 is a plan view of a connection 9d between a resonator plate 9a and an anchor 9c of a semiconductor device 9 of a comparative example. A perpendicular line D2 in the cleavage plane direction D1 meets a recess on the positive side of the X-axis of the single-crystal layer 12 at the connection between the resonator plate 9a and the anchor 9c at a junction point S. The perpendicular line D2 and the side of the single-crystal layer 12 of the resonator plate 9a on the positive side of the X-axis intersect at an intersection point B91, and the distance between the intersection point B91 and the junction point S is a distance L91. The perpendicular line D2 and the side of the single-crystal layer 12 of the anchor 9c on the negative side of the X-axis intersect at an intersection point B92, and the distance between the intersection point B92 and the junction point S is a distance L92. Because the distance L91 is longer than the distance L92, the single-crystal layer 12 at the junction point S is subjected to a tensile stress based on the distance L91.

[0040] FIG. 10 is an enlarged plan view of a region 9d1 of a connection portion 9d between the resonator plate 9a and the anchor 9c in FIG. 9 . The shape of the recess on the positive side of the X axis of the single-crystalline layer 12 of the comparative example is a shape that is rounded during manufacturing from a shape patterned at a right angle, and the radius of curvature of the curve of the recess is, for example, one-tenth or less of the distance L91. The recess of the single-crystalline layer 12 is perpendicular to the cleavage plane direction D1 at the contact point S, but the radius of curvature of the curve passing through the contact point S is small, resulting in a structure in which stress concentrates at the contact point S. Because the semiconductor device 9 of the comparative example has a structure in which stress concentrates at the contact point S, cracks CR6 are likely to occur along the cleavage plane direction D1 when tensile stress is generated in the direction perpendicular to the single-crystalline layer 12 (D2), making the device susceptible to breakage. In contrast, the crack prevention structure of the semiconductor device 1 according to the first embodiment of the present disclosure has a structure in which the radius of curvature of the recess is set to a predetermined length or more and a portion nearly perpendicular to the cleavage plane direction is wide, preventing tensile stress from concentrating at the contact point.

[0041] (Effects of the first embodiment) The crack prevention structure of the semiconductor device 1 according to the first embodiment includes a substrate 11 and a single crystal layer 12 that is a single crystal layer stacked on the main surface of the substrate 11. In the crack prevention structure, the radius of curvature of the recess at a contact point S between a perpendicular line D2 to the cleavage plane direction D1 and the recess in the single crystal layer 12 is set to a distance L3 that is longer than a distance L1 that is the maximum length of the single crystal layer 12 on the perpendicular line D2 passing through the contact point S. According to the crack prevention structure of the semiconductor device 1 according to the first embodiment, the recess in the single crystal layer 12 has a structure that prevents stress concentration. Therefore, even if tensile stress is generated in the single crystal layer 12 in the direction of the perpendicular line D2, cracks are unlikely to occur in the cleavage plane direction D1, and the structure is unlikely to break.

[0042] [Second embodiment] (Configuration of semiconductor devices) Fig. 11 is a plan view illustrating a crack prevention structure of a semiconductor device 1 according to a second embodiment. The overall plan view of the semiconductor device 1 according to the second embodiment is similar to the plan views of the semiconductor device 1 according to the first embodiment shown in Fig. 1 and Fig. 3, and therefore a description thereof will be omitted. Fig. 11 shows an enlarged view of a region 1d in Fig. 3, which includes the connection portion between the resonator plate 1a and the anchor 1c and part of the gap 14.

[0043] FIG. 12 is an enlarged plan view of region 1d1 of the crack prevention structure of FIG. 11. The recess of the single-crystal layer 12 includes a recess line E2, which is a line overlapping with the perpendicular line D2. The crack prevention structure of FIG. 12 has a shape in which the recess of the single-crystal layer 12 is chamfered in a direction perpendicular to the cleavage plane direction D1, and corresponds to a case in which the radius of curvature of the crack prevention structure of the semiconductor device 1 of the first embodiment shown in FIG. 7 is infinite. Both ends of the recess line E2 are connected to curves with large radii of curvature, and the curves with large radii of curvature are connected to a line along the X direction or a line along the Y direction. Each curve connecting both ends of the recess line E2 may have a shape achieved by rounding the corners of the chamfered recess of the single-crystal layer 12 during manufacturing. Since the entire recess line E2 is perpendicular to the cleavage plane direction D1 and is connected to a curve with large radii of curvature, stress does not concentrate. Since the recesses of the single crystal layer 12 have a structure that prevents stress from concentrating, even if tensile stress occurs in the direction of the perpendicular line D2 of the single crystal layer 12 connected to the contact S, cracks are unlikely to occur in the cleavage plane direction D1 and the single crystal layer 12 is unlikely to break.

[0044] 12 is viewed from a direction parallel to the XY plane, forms a plane defined by a set of lines connecting in the Z direction the recess line E2 on the main surface of the single crystal layer 12 and the projection line of the recess line E2 projected from the Z direction onto the bottom surface of the single crystal layer 12. In the XY plane obtained by cutting the single crystal layer 12 at an arbitrary height, the recess line E2 is defined by the projection from the Z direction of a line that overlaps with the perpendicular line D2.

[0045] (Effects of the second embodiment) The crack prevention structure of the semiconductor device 1 according to the second embodiment has a recess line E2 that is a straight line that intersects perpendicularly to the cleavage plane direction D1 at a contact point S between a perpendicular line D2 to the cleavage plane direction D1 and the recess in the single crystal layer 12. According to the crack prevention structure of the semiconductor device 1 according to the second embodiment, the recess in the single crystal layer 12 has a structure that does not concentrate stress, so that even if tensile stress is generated in the single crystal layer 12 in the direction of the perpendicular line D2, cracks are unlikely to occur in the cleavage plane direction D1 and the structure is unlikely to break. Furthermore, the crack prevention structure of the semiconductor device 1 according to the second embodiment can be realized by chamfering the recess in the single crystal layer 12 in a direction perpendicular to the cleavage plane direction D1, which makes it easier to process during manufacturing.

[0046] [Third embodiment] (Configuration of semiconductor devices) Fig. 13 is an enlarged plan view of region 1d1 of the crack prevention structure of the semiconductor device 1 according to the third embodiment. The overall plan view of the semiconductor device 1 according to the third embodiment is similar to the plan views of the semiconductor device 1 according to the first embodiment shown in Figs. 1 and 3, and therefore a description thereof will be omitted. Fig. 13 shows an enlarged view of region 1d1 in Fig. 4, which is an enlarged plan view of region 1d including the connection portion between the resonator plate 1a and the anchor 1c and part of the gap 14 shown in Fig. 3.

[0047] In FIG. 13, holes H1 to H7 are formed in the single crystal layer 12 near the recess. The shapes of holes H1 to H7 as viewed from the Z direction are, for example, circular. Hole H1 is arranged so that the circumference of hole H1 intersects with a straight line in the cleavage plane direction D1 that passes through the perpendicular line D2 and the tangent point S of the recess. The distance between point P1 where hole H1 first intersects with the cleavage plane direction D1 and tangent point S is, for example, about several microns. The straight line that passes through tangent point S and the center of hole H1 intersects with the cleavage plane direction D1 obliquely.

[0048] Hole H2 is arranged such that its circumference intersects with a line extending from a line indicating the diameter of hole H1 that is parallel to the cleavage plane direction D1 in the cleavage plane direction D1, and a line passing through the center of hole H2 and the center of hole H1 intersects obliquely with the cleavage plane direction D1. The distance between hole H1 and hole H2 may be, for example, several microns. Similarly, hole H3 is arranged such that its circumference intersects with a line extending from a line indicating the diameter of hole H2 that is parallel to the cleavage plane direction D1 in the cleavage plane direction D1, and a line passing through the center of hole H3 and the center of hole H2 intersects obliquely with the cleavage plane direction D1. Hole H4 is also arranged at a position similarly defined relative to hole H3. The distances between holes H2, H3, and H4 may each be, for example, several microns.

[0049] Hole H5 is positioned such that its circumference intersects with a line in the cleavage plane direction D1 that passes through the perpendicular line D2 and the tangent point S of the recess. A line passing through the tangent point S and the center of hole H5 intersects obliquely with the cleavage plane direction D1. Hole H6 is positioned such that its circumference intersects with a line extending in the cleavage plane direction D1 from a line indicating the diameter of hole H5 that is parallel to the cleavage plane direction D1, and a line passing through the center of hole H6 and the center of hole H5 intersects obliquely with the cleavage plane direction D1. Hole H7 is also positioned at a position similarly defined with respect to hole H6. The distance between holes H5, H6, and H7 may each be, for example, several microns.

[0050] As described above, the crack prevention structure of the semiconductor device 1 according to the third embodiment shown in FIG. 13 includes a plurality of holes H1 to H7, and a straight line passing through the mutual centers of adjacent holes intersects obliquely with the cleavage plane direction D1.

[0051] 14 is a cross-sectional view taken along line XIV-XIV near hole H4 of the crack prevention structure of the semiconductor device 1 according to the third embodiment shown in FIG. 13. Hole H4 is formed to penetrate the single-crystal layer 12 and has a rectangular cross section. That is, hole H4 has a cylindrical shape. Here, a thin single-crystal layer 12 may remain on the main surface of the substrate 11 in hole H4.

[0052] FIG. 15 is an enlarged plan view of the crack prevention structure of the semiconductor device 1 according to the third embodiment shown in FIG. 13 when a crack occurs in the single-crystal layer 12 near the recess. A crack CR1 occurs from the contact point S of the recess along the cleavage plane direction D1. When the crack CR1 reaches the hole H1, the crack stops along the line in the cleavage plane direction D1 because the single-crystal layer 12 is thin or absent at the hole H1. If the tensile stress in the direction perpendicular to the line D2 of the single-crystal layer 12 is still strong, a crack CR2 then occurs in a direction parallel to the cleavage plane direction D1 from the point where the line representing the diameter of the hole H1, which is parallel to the cleavage plane direction D1, intersects with the circumference of the hole H1. When the crack CR2 reaches the hole H2, the crack stops along the line parallel to the cleavage plane direction D1 because the single-crystal layer 12 is thin or absent at the hole H2.

[0053] If the tensile stress in the direction of the perpendicular line D2 of the single crystal layer 12 is still strong, a crack CR3 will then occur in a direction parallel to the cleavage plane direction D1 from the point where a line showing the diameter of the hole H2, which is parallel to the cleavage plane direction D1, intersects with the circumference of the hole H2. When the crack CR3 reaches the hole H3, the cracking on the line parallel to the cleavage plane direction D1 stops because there is no single crystal layer 12 or the single crystal layer 12 is thin at the hole H3. If the tensile stress still remains, the crack will stop on the line parallel to the cleavage plane direction D1 when it reaches the hole H4.

[0054] Furthermore, if the tensile stress in the direction of the perpendicular line D2 of the single crystal layer 12 becomes even stronger and the crack CR1 stops at the hole H1 and then extends in the cleavage plane direction D1, when the crack reaches the hole H5, the crack stops along the line in the cleavage plane direction D1 because there is no single crystal layer 12 or the single crystal layer 12 is thin at the hole H5. If the tensile stress in the direction of the perpendicular line D2 of the single crystal layer 12 is still strong, a crack will occur from the hole H5 to the hole H6 and further from the hole H6 to the hole H7, but when the crack reaches the hole H6 or the hole H7, the crack stops along the line parallel to the cleavage plane direction D1. The number and positions of the holes to be arranged can be determined based on the tensile stress generated, the radius of curvature of the recess, etc., and can be determined as needed to stop the crack.

[0055] In the crack prevention structure of the semiconductor device 1 according to the third embodiment, holes H1 to H7 guide the location of the crack to a position that is shifted from the straight line in the cleavage plane direction D1 that passes through the contact point S, thereby dispersing the stress and preventing cracking from occurring in the cleavage plane direction D1 from the contact point S.

[0056] (Effects of the third embodiment) The crack prevention structure of the semiconductor device 1 according to the third embodiment has a hole H1 formed in the single crystal layer 12 near the recess, and a line passing through the contact point S and the center of the hole H1 obliquely intersects the cleavage plane direction D1. The crack prevention structure also includes holes H2 to H7, and a line passing through the centers of adjacent holes among the multiple holes H1 to H7 obliquely intersects the cleavage plane direction D1. According to the crack prevention structure of the semiconductor device 1 according to the third embodiment, holes H1 to H7 guide the location of crack generation to a position shifted from the line in the cleavage plane direction D1 passing through the contact point S, and stress is dispersed, preventing cracks from extending in the cleavage plane direction D1, resulting in a structure that is less susceptible to cracking.

[0057] [Fourth embodiment] (Configuration of semiconductor devices) Fig. 16 is an enlarged plan view of region 1d1 of the crack prevention structure of the semiconductor device 1 according to the fourth embodiment. The overall plan view of the semiconductor device 1 according to the fourth embodiment is similar to the plan views of the semiconductor device 1 according to the first embodiment shown in Figs. 1 and 3, and therefore a description thereof will be omitted. Fig. 16 shows an enlarged view of region 1d1 in Fig. 4, which is an enlarged plan view of region 1d including the connection portion between the resonator plate 1a and the anchor 1c and part of the gap 14 shown in Fig. 3.

[0058] 16, a first groove T1 is formed in the single crystal layer 12 near the recess. The shape of the first groove T1 when viewed from the Z direction is, for example, rectangular. The first groove T1 is disposed perpendicular to the cleavage plane direction D1 so that the center of the longitudinal direction intersects with a straight line in the cleavage plane direction D1 that passes through a perpendicular line D2 and a contact point S of the recess. The distance between the contact point S and a point P2 where the straight line in the cleavage plane direction D1 and the first groove T1 intersect is, for example, about several microns.

[0059] 17 is a cross-sectional view taken along line XVII-XVII near the first groove T1 of the crack prevention structure of the semiconductor device 1 according to the fourth embodiment shown in FIG. 16. The first groove T1 is formed to penetrate the single-crystal layer 12 and has a rectangular cross section. That is, the shape of the first groove T1 is a rectangular parallelepiped. Here, a thin single-crystal layer 12 may remain on the main surface of the substrate 11 in the first groove T1.

[0060] FIG. 18 is an enlarged plan view of the crack prevention structure of the semiconductor device 1 according to the fourth embodiment shown in FIG. 16 when a crack occurs in the single-crystal layer 12 near the recess. A crack CR4 occurs from the contact point S of the recess along the cleavage plane direction D1. When the crack CR4 reaches the first groove T1, the crack stops along the cleavage plane direction D1 because the single-crystal layer 12 is thin or absent in the first groove T1. Even if the tensile stress in the direction perpendicular to the cleavage plane direction D2 of the single-crystal layer 12 is still strong, stress concentration is prevented because the longitudinal direction of the first groove T1 is perpendicular to the cleavage plane direction D1. In the crack prevention structure of the semiconductor device 1 according to the fourth embodiment, the crack stops due to the first groove T1, and stress concentration is prevented due to the longitudinal direction of the first groove T1, so cracking from the contact point S in the cleavage plane direction D1 is prevented.

[0061] (Effects of the fourth embodiment) The crack prevention structure of the semiconductor device 1 according to the fourth embodiment has a first groove T1 formed in the single crystal layer 12 near the recess, the first groove T1 having a longitudinal direction intersecting a line parallel to the cleavage plane direction D1 and passing through the contact point S. According to the crack prevention structure of the semiconductor device 1 according to the fourth embodiment, cracks are stopped by the first groove T1, and stress concentration is prevented by the longitudinal direction perpendicular to the cleavage plane direction D1, so that cracks do not propagate in the cleavage plane direction D1, resulting in a structure that is less susceptible to cracking.

[0062] [Fifth embodiment] (Configuration of semiconductor devices) Fig. 19 is an enlarged plan view of region 1d1 of the crack prevention structure of the semiconductor device 1 according to the fifth embodiment. The overall plan view of the semiconductor device 1 according to the fifth embodiment is similar to the plan views of the semiconductor device 1 according to the first embodiment shown in Figs. 1 and 3, and therefore a description thereof will be omitted. Fig. 19 shows an enlarged view of region 1d1 in Fig. 4, which is an enlarged plan view of region 1d including the connection portion between the resonator plate 1a and the anchor 1c and part of the gap 14 shown in Fig. 3.

[0063] 19, a second groove T2 is formed in the single-crystal layer 12 near the recess. The shape of the second groove T2 as viewed from the Z direction has a starting point P3 on a line in the cleavage plane direction D1 that passes through the junction S, and is a thick parabolic shape that moves away from the line in the cleavage plane direction D1 as it moves away from the junction S. At the end point of the second groove T2, the second groove T2 is tangent to a perpendicular line D3 that perpendicularly intersects with the cleavage plane direction D1 at a position P4, and is oriented parallel to the perpendicular line D3. The distance between the starting point P3 of the second groove T2 and the junction S is, for example, about several microns.

[0064] The cross-sectional view taken along line XIX-XIX in the vicinity of the second groove T2 shown in FIG. 19 is similar to the cross-sectional view in the vicinity of the first groove T1 shown in FIG. 17, and therefore a description thereof will be omitted.

[0065] FIG. 20 is an enlarged plan view of the crack prevention structure of the semiconductor device 1 according to the fifth embodiment shown in FIG. 19 when a crack occurs in the single-crystal layer 12 near the recess. A crack CR5 occurs from the contact point S of the recess in the cleavage plane direction D1. When the crack CR5 reaches the second groove T2, the crack stops along the cleavage plane direction D1 because the single-crystal layer 12 is absent or thin at the second groove T2. Even if the tensile stress in the direction perpendicular to the cleavage plane direction D2 of the single-crystal layer 12 is still strong, the second groove T2 bends from a direction parallel to the cleavage plane direction D1 to a direction perpendicular thereto, thereby guiding the crack from a direction prone to cracking to a direction less prone to cracking and stopping its propagation. In the crack prevention structure of the semiconductor device 1 according to the fifth embodiment, the second groove T2 changes the crack direction and stops its propagation, preventing cracking from the contact point S in the cleavage plane direction D1.

[0066] (Effects of the fifth embodiment) The crack prevention structure of the semiconductor device 1 according to the fifth embodiment has a second groove T2 formed in the single crystal layer 12 near the recess. The second groove T2 has a start point P3 on a line in the cleavage plane direction D1 that passes through the contact point S, and has a parabolic shape with a thickness that increases from the line in the cleavage plane direction D1 as it moves away from the contact point S. According to the crack prevention structure of the semiconductor device 1 according to the fifth embodiment, the second groove T2 changes the direction of cracks and stops their propagation, so that cracks do not propagate from the contact point S of the single crystal layer 12 in the cleavage plane direction D1, resulting in a crack-resistant structure.

[0067] [Other embodiments] Although several embodiments of the present disclosure have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. One or more elements of one embodiment can be combined with one or more elements of another embodiment. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0068] For example, in the semiconductor device 1 according to the first to fifth embodiments of the present disclosure, a crack prevention structure is provided at the connection between the resonator's resonant plate 1a and anchor 1c, but similarly, a crack prevention structure may be provided at the connection between the resonant plate 1a and anchor 1b.

[0069] For example, any of the crack prevention structures for the semiconductor device 1 according to the first or second embodiment of the present disclosure may be combined with one or more of the crack prevention structures for the semiconductor device 1 according to the third to fifth embodiments.

[0070] Furthermore, for example, in the crack prevention structures of the semiconductor device 1 according to the third to fifth embodiments of the present disclosure, the holes and grooves formed in the single crystal layer 12 have spaces. However, other materials, such as metal materials, may be embedded within the spaces as long as they have the function of stopping cracks.

[0071] Furthermore, for example, in the semiconductor devices 1 according to the first to fifth embodiments of the present disclosure, the single crystal layer 12 is laminated on the main surface of the substrate 11. However, a buffer layer that inherits the crystalline information of the substrate may be laminated on the main surface of the substrate 11, and the single crystal layer 12 may be laminated on the main surface of the buffer layer.

[0072] Furthermore, for example, in the semiconductor device 1 according to the first to fifth embodiments of the present disclosure, the substrate 11 is a single-crystal silicon substrate with the (111) plane exposed, but the substrate 11 may also be a single-crystal silicon carbide SiC substrate.

[0073] Furthermore, for example, in the semiconductor devices 1 according to the first to fifth embodiments of the present disclosure, the single crystal layer 12 is single crystal aluminum nitride AlN. However, the single crystal layer 12 may be zinc oxide ZnO, lithium niobate LiNbO3, lithium tantalate LiTaO3, or lead zirconate titanate PZT.

[0074] For example, the semiconductor device 1 according to the first to fifth embodiments of the present disclosure is a resonator. However, the semiconductor device 1 may be a high-frequency switch, a filter, or a resonator for an oscillator. The semiconductor device 1 may also be a MEMS device other than these.

[0075] (Addendum) The technical ideas that can be understood from the present disclosure are described below. Note that, for the purpose of aiding understanding and not intending to be limiting, the components described in the appendices are given the reference numerals of the corresponding components in the embodiments. The reference numerals are shown as examples to aid understanding, and the components described in each appendix should not be limited to the components indicated by the reference numerals.

[0076] (Appendix 1) The crack prevention structure for a laminated film includes a substrate 11 and a single crystal layer 12 made of a material different from that of the substrate 11, stacked on the main surface of the substrate 11. When the single crystal layer 12 is viewed from the normal direction to the main surface of the substrate 11, the radius of curvature of a recess curve E1, which is a recess at a contact point S between a perpendicular D2 to the cleavage plane direction D1 of the single crystal layer 12 and the recess in the single crystal layer 12, is set to a predetermined value or more. According to the crack prevention structure, the recess in the single crystal layer 12 is structured to prevent stress concentration, so that even if tensile stress is generated in the single crystal layer 12 in the direction of the perpendicular D2, cracks are unlikely to occur in the cleavage plane direction D1, and the structure is unlikely to break.

[0077] (Appendix 2) In the crack prevention structure of the laminated film described in Appendix 1, the distance L3, which is the radius of curvature of the recess, is longer than the distance L1, which is the maximum length of the single crystal layer 12 on the perpendicular line D2 passing through the contact point S. According to the crack prevention structure, the recess of the single crystal layer 12 has a structure in which stress is not concentrated, so that even if tensile stress is generated in the single crystal layer 12 in the direction of the perpendicular line D2, cracks are unlikely to occur in the cleavage plane direction D1, and the structure is unlikely to break.

[0078] (Appendix 3) In the crack prevention structure of the laminated film described in Supplementary Note 1, the recess has a recess line E2 that is a straight line portion that intersects perpendicularly to the cleavage plane direction D1 at the contact point S. According to the crack prevention structure, the recess in the single crystal layer 12 is structured so that stress does not concentrate, and therefore, even if tensile stress in the direction of the perpendicular line D2 occurs in the single crystal layer 12, cracks are unlikely to occur in the cleavage plane direction D1 and the structure is unlikely to break. Furthermore, the crack prevention structure can be realized by chamfering the recess in the single crystal layer 12 in a direction perpendicular to the cleavage plane direction D1, which makes it easier to process during manufacturing.

[0079] (Appendix 4) The crack prevention structure for the laminated film according to any one of Supplementary Notes 1 to 3 has a hole H1 formed in the single crystal layer 12 near the recess, and a line passing through the contact point S and the center of the hole H1 obliquely intersects with the cleavage plane direction D1. According to the crack prevention structure, the location of crack occurrence is guided to a position shifted from the line passing through the contact point S in the cleavage plane direction D1, thereby making the structure less susceptible to cracking.

[0080] (Appendix 5) The crack prevention structure of the laminated film described in Supplementary Note 4 includes a plurality of holes H1 to H7, and a straight line passing through adjacent holes intersects the cleavage plane direction D1 obliquely. According to the crack prevention structure, holes H1 to H7 guide the location of crack occurrence to a position shifted from the straight line in the cleavage plane direction D1 passing through the contact point S, and stress is dispersed, so that cracks do not propagate in the cleavage plane direction D1, resulting in a structure that is less likely to break.

[0081] (Appendix 6) The crack prevention structure of the laminated film described in any one of Supplementary Notes 1 to 5 further includes a first groove T1 formed in the single crystal layer 12 near the recess, the first groove T1 having a longitudinal direction intersecting a line parallel to the cleavage plane direction D1 passing through the contact point S. According to the crack prevention structure, cracks are stopped by the first groove T1, and stress concentration is prevented by the longitudinal direction perpendicular to the cleavage plane direction D1. Therefore, even if tensile stress is generated in the direction of the perpendicular line D2, cracks do not propagate in the cleavage plane direction D1, resulting in a structure that is less susceptible to cracking.

[0082] (Appendix 7) The crack prevention structure for the laminated film described in any one of Supplementary Notes 1 to 6 further includes a second groove T2 formed in the single-crystal layer 12 near the recess. The second groove T2 has a start point P3 on a line parallel to the cleavage plane direction D1 passing through the contact point S, and has a parabolic shape that deviates from the line as it moves away from the contact point S. According to the crack prevention structure, the second groove T2 changes the direction of a crack and stops its propagation. Therefore, even if tensile stress is generated in the direction of the perpendicular line D2, the crack will not propagate from the contact point S of the single-crystal layer 12 in the cleavage plane direction D1, resulting in a crack-resistant structure.

[0083] (Appendix 8) In the structure for preventing cracks in a laminated film according to any one of Supplementary Notes 1 to 7, the substrate 11 is made of single-crystal silicon with the (111) plane exposed. The cleavage plane direction D1 of the single-crystal layer 12 is parallel to the (-101) plane, the cleavage plane direction DL is parallel to the (0-11) plane, and the cleavage plane direction DV is parallel to the (-110) plane. The crack prevention structure makes it difficult for the single-crystal layer 12, which is laminated on the main surface of the single-crystal silicon with the (111) plane exposed, to crack in directions parallel to the (-101), (0-11), and (-110) planes.

[0084] (Appendix 9) The semiconductor device 1 includes the crack prevention structure of the laminated film according to any one of Supplementary Notes 1 to 8. The recesses of the single crystal layer 12 are less likely to crack in the cleavage plane direction D1, making it possible to provide a semiconductor device 1 that is less likely to break.

[0085] (Appendix 10) In the semiconductor device 1 described in Supplementary Note 9, the single crystal layer 12 is a piezoelectric film. A recess in the piezoelectric film is less likely to crack in the cleavage plane direction D1, and the semiconductor device 1 is less likely to break.

[0086] (Appendix 11) The semiconductor device 1 described in Supplementary Note 10 is a resonator having electrodes on a piezoelectric film. The recesses in the piezoelectric film make it difficult for cracks to occur in the cleavage plane direction D1, providing a resonator that is difficult to break. [Explanation of symbols]

[0087] 1. Semiconductor devices 1a Resonance plate 1b, 1c anchor 1d, 1d1 area 11 Circuit Board 12 Single crystal layer 13a, 13b electrode 14 void C1 Arc CR1~CR6 crack D1, DL, DV Cleavage plane direction D2, D3 perpendicular lines E1, EL concave curves E2 Concave Straight Line H1~H7 holes Distance between L1 and L3 Points P1 and P2 P3 Starting Point P4 position S and SL contacts T1, First Ditch T2, 2nd trench

Claims

1. A substrate; a single-crystal layer made of a material different from that of the substrate and stacked on a main surface of the substrate; and when the single crystal layer is viewed from a normal direction of the main surface of the substrate, a radius of curvature of the recess at a contact point between a perpendicular to a cleavage plane direction of the single crystal layer and the recess of the single crystal layer is set to a predetermined value or more. Crack prevention structure of laminated film.

2. 2. The structure for preventing cracks in a laminated film according to claim 1, wherein the radius of curvature of the recess is longer than the maximum length of the single crystal layer in the perpendicular line passing through the contact point.

3. 2. The structure for preventing cracks in a laminated film according to claim 1, wherein the recess has a linear portion that intersects perpendicularly with the direction of the cleavage plane at the contact point.

4. 4. A crack prevention structure for a laminated film according to claim 1, further comprising a hole formed in the single crystal layer near the recess, wherein a straight line passing through the contact point and the center of the hole intersects the cleavage plane direction obliquely.

5. 5. The structure for preventing cracks in a laminated film according to claim 4, wherein the structure includes a plurality of the holes, and a straight line passing through the centers of adjacent holes intersects the cleavage plane direction obliquely.

6. 4. A crack prevention structure for a laminated film described in any one of claims 1 to 3, further comprising a first groove formed in the single crystal layer near the recess and having a longitudinal direction that intersects with a line passing through the contact and parallel to the cleavage plane direction.

7. 4. The laminated film crack prevention structure according to claim 1, further comprising a second groove formed in the single crystal layer near the recess, the second groove having a starting point on a straight line passing through the contact point and parallel to the cleavage plane direction, and a parabolic shape that deviates from the straight line as it moves away from the contact point.

8. the substrate is made of single-crystal silicon with the (111) plane exposed; 4. The laminated film crack prevention structure according to claim 1, wherein the cleavage plane direction of the single crystal layer is a direction parallel to the (-101) plane, a direction parallel to the (0-11) plane, or a direction parallel to the (-110) plane.

9. A semiconductor device comprising the crack prevention structure of the laminated film according to any one of claims 1 to 3.

10. The semiconductor device of claim 9 , wherein the single crystal layer is a piezoelectric film.

11. The semiconductor device according to claim 10, which is a resonator having electrodes on the piezoelectric film.

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