JP5541772B2 - Electrode structure - Google Patents

Description

  The present invention relates to an electrode structure formed using semiconductor processing technology.

  FIG. 17 is a cross-sectional view showing a conventional electrode structure, and shows a thin film structure 101 included in the electrode structure. The thin film structure 101 includes a support portion 103 and a floating portion 105 supported by the support portion 103, and is formed on the substrate 107 using a conductive material. The floating portion 105 is disposed at a predetermined interval from the substrate 107 and protrudes outward from the upper portion of the support portion 103.

  The substrate 107 includes a substrate body 111, a first insulating film 113, a wiring 115, and a second insulating film 117. The first insulating film 113 is formed on the substrate body 111. A wiring 115 is provided on the surface of the first insulating film 113, and the surface of the first insulating film 113 and the surface of the wiring 115 are planarized with almost no step. The second insulating film 117 covers the surface and side surfaces of the wiring 115 and the first insulating film 113. However, the second insulating film 117 has a hole 117a that is opened on the surface of the wiring 115, and the surface of the wiring 115 is selectively exposed here. A support portion 103 is formed on the wiring 115 through a hole 117a.

  14 to 16 are cross-sectional views sequentially showing a manufacturing process of a conventional thin film structure. First, as shown in FIG. 14, a sacrificial film 121 is formed on the entire surface of the substrate 107. However, at this stage, the second insulating film 117 does not have the hole 117 a in the substrate 107.

  Next, dry etching is performed from the surface side of the sacrificial film 121, an opening 121a is formed in the sacrificial film 121, a hole 117a is formed in the second insulating film 117, and an anchor hole 122 is formed, so that the surface of the wiring 115 is selectively formed. To expose. Thereby, the structure shown in FIG. 15 is obtained.

  Subsequently, as illustrated in FIG. 16, a thin film layer 123 is formed using a conductive material on the sacrificial film 121 and the substrate 107 exposed through the anchor hole 122.

  Thereafter, the thin film layer 123 is selectively removed, and the thin film layer 123 thus patterned forms the thin film structure 101. Subsequently, the sacrificial film 121 is removed to obtain the structure shown in FIG. Of the remaining part of the thin film layer 123, the part fitted in the anchor hole 122 becomes the support part 103, and the part located on the sacrificial film 121 becomes the floating part 105.

  In such a conventional manufacturing method, it is desirable to form the sacrificial film 121 with a material that can be easily removed by etching. For example, a silicon oxide film is employed. On the other hand, a silicon substrate is employed for the substrate body 111 in order to use a semiconductor processing technology that facilitates fine processing. In order to easily form the first insulating film 113 on the silicon substrate, a silicon oxide film is also used for the first insulating film 113 in the same manner as the sacrificial film 121.

  In order to prevent the first insulating film 113 from being etched when the sacrificial film 121 is removed by etching, the second insulating film 117 is not easily etched with respect to the etching of the silicon oxide film and is easy to process. For example, a silicon nitride film is employed.

  However, if the second insulating film 117 completely exposes the surface of the wiring 115, the etchant used for etching the sacrificial film 121 penetrates between the side surface of the wiring 115 and the second insulating film 117, The possibility of reaching the first insulating film 113 is increased.

  FIG. 18 is a plan view of the structure shown in FIG. 15 viewed from the opening side of the anchor hole 122. Thus, when the shape of the anchor hole 122 in plan view has a steep corner such as a rectangle or a square, the stress tends to concentrate on this corner. For this reason, the sacrificial film 121, the first insulating film 113, and the second insulating film 117 are likely to crack from this corner. In particular, when the second insulating film 117 is formed using a silicon nitride film, the residual stress is in the tensile direction, while the residual stress in the sacrificial film 121 and the first insulating film 113 that are silicon oxide films is in the compression direction. It is considered that cracks are more likely to occur. The occurrence of such cracks is not only a problem of strength per se, but also increases the possibility that the etchant used for etching the sacrificial film 121 reaches the first insulating film 113 as described above. But it becomes a problem.

  An object of this invention is to provide the electrode structure which suppresses generation | occurrence | production of a crack.

A first aspect of the electrode structure according to the present invention includes a wiring (45) selectively disposed on the first insulating film (33), an edge (on the surface of the wiring, covering the first insulating film). 45a) has a hole (47c) that enters the inside of the wiring by a first predetermined distance (d1) and selectively exposes the surface of the wiring, and selectively covers the wiring. The second insulating film (47) having a different direction of residual stress from the insulating film, the surface of the wiring selectively exposed through the hole , and the second predetermined distance (d2) from the hole. supporting portion connected to a surface of the second insulating film and (23b), supported by said support portion and the second insulating film and a floating portion spaced a predetermined distance (23a) and a conductive thin film structure to have a With.
The support portion exhibits a polygon or an ellipse with rounded corners (51r) in plan view in a region connected to the surface of the second insulating film.

  The 2nd aspect of the electrode structure concerning this invention is a 1st aspect of an electrode structure, Comprising: The said support part (23b) covers the said hole (47c).

  In the second structure of the electrode structure, for example, the residual stress of the first insulating film (33) is a compressive stress, and the residual stress of the second insulating film is a tensile stress. Further, for example, the first insulating film (33) is an oxide film, and the second insulating film is a nitride film.

  A third aspect of the electrode structure according to the present invention is the first aspect of the electrode structure, wherein the hole (47c) has a polygon or an ellipse with rounded corners (47r) in plan view. .

  In the electrode structure of the present invention, preferably, the surface of the first insulating film and the surface of the wiring are on the same plane.

According to a first aspect of the electrode structure, the direction of residual stress hole of the second insulating film different from the first insulating film are separated by the edge portion and the first predetermined distance of the surface of the wiring, both The shear stress acting during In addition, since the region connected to the surface of the second insulating film of the support portion has no corners in the planar shape, concentration of residual stress can be avoided and the occurrence of cracks is suppressed.

  According to the second aspect of the electrode structure, since the support portion is connected to both the second insulating film and the wiring formed on the first insulating film, both the first insulating film and the second insulating film are used. Reduce the possibility of peeling.

  According to the third aspect of the electrode structure, since there is no corner in the planar shape in the hole, concentration of residual stress can be avoided, and the occurrence of cracks is suppressed.

  The objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

It is a top view which shows the structure of the principal part of a semiconductor acceleration sensor which can apply the manufacturing method of the electrode structure concerning this invention, and a thin film structure. It is AA sectional drawing of FIG. FIG. 3 is a cross-sectional view showing a manufacturing process of the structure shown in FIG. 2. FIG. 3 is a cross-sectional view showing a manufacturing process of the structure shown in FIG. 2. FIG. 3 is a cross-sectional view showing a manufacturing process of the structure shown in FIG. 2. FIG. 3 is a cross-sectional view showing a manufacturing process of the structure shown in FIG. 2. FIG. 3 is a cross-sectional view showing a manufacturing process of the structure shown in FIG. 2. FIG. 3 is a cross-sectional view showing a manufacturing process of the structure shown in FIG. 2. FIG. 3 is a cross-sectional view showing a manufacturing process of the structure shown in FIG. 2. It is a top view of an anchor hole vicinity. It is a top view of an anchor hole vicinity. It is a top view of an anchor hole vicinity. It is a top view of an anchor hole vicinity. It is sectional drawing which shows the manufacturing process of the conventional thin film structure in order. It is sectional drawing which shows the manufacturing process of the conventional thin film structure in order. It is sectional drawing which shows the manufacturing process of the conventional thin film structure in order. It is sectional drawing which shows the conventional electrode structure. It is a top view which shows the conventional electrode structure.

A. Embodiment 1 FIG.
FIG. 1 is a plan view showing a configuration of a main part of a semiconductor acceleration sensor 100 to which the method for manufacturing a thin film structure according to the present invention can be applied. 2 is a cross-sectional view taken along the line AA in FIG. The semiconductor acceleration sensor 100 includes a substrate 1 that is a sensor substrate, and a sensor unit 3 that is formed above the substrate 1 (front side in FIG. 1) and has a function of detecting acceleration.

  The sensor unit 3 includes a movable mass body 21, a plurality of fixed structures 23, and a plurality of beams 25, and is formed as a thin film structure. The thin film structure is formed using a conductive material, for example, doped polysilicon obtained by doping polysilicon with an impurity such as phosphorus.

  The mass body 21 has a plurality of movable electrode portions 21a extending along a direction C perpendicular to the direction B of acceleration to be detected. The fixed structure 23 includes a fixed electrode portion 23a extending along the direction C and a support portion 23b that supports the fixed electrode portion 23a. The fixed electrode portions 23a are provided at predetermined intervals along the direction B. The plurality of fixing structures 23 are connected to one of the wirings 43 and 45 by the support portion 23b. However, the application of the present invention does not depend on which of the wirings 43 and 45 the fixing structure 23 is connected to.

  As shown in FIG. 2, the fixed electrode portion 23 a is arranged at a predetermined interval from the substrate 1 and floats. The support portion 23b is connected to the substrate 1, more specifically, to the wiring 45 at the position AA. The movable electrode portion 21a is also arranged at a predetermined interval from the substrate 1 in the same manner as the fixed electrode portion 23a.

  The beam 25 is formed integrally with the mass body 21 and suspends the mass body 21 above the substrate 1. Each beam 25 includes a support portion 25a that protrudes upward from the substrate 1, a spring portion 25c that is provided at an end edge in the direction B of the mass body 21, and a coupling portion 25b that couples the support portion 25a and the spring portion 25c. It has. The spring portion 25c is elastically bent and deformed at least along the direction B. Thereby, the mass body 21 can move along the direction B while having a restoring force. One of the support portions 25a is connected to the wiring 41 below the support portion 25a.

  The fixed electrode portions 23a and the movable electrode portions 21a are alternately arranged with an interval in the direction B. When acceleration along the direction B is applied to the acceleration sensor 100, the mass body 21 moves and the distance between the movable electrode portion 21a and the fixed electrode portion 23a changes. Therefore, the applied acceleration can be detected by measuring the capacitance created by the movable electrode portion 21a and the fixed electrode portion 23a from the outside using the wirings 41, 43, and 45.

  As shown in FIG. 2, the substrate 1 includes a substrate body 31, an oxide film 33, wirings 43 and 45, and a nitride film 47. Further, as shown in FIG. 1, wiring 41 is also provided. The oxide film 33 is provided on the substrate body 31. The surface of the oxide film 33 is flat, and the wirings 41, 43 and 45 are formed on the oxide film 33. For example, the surface of the oxide film 33 and the surfaces of the wirings 41, 43, and 45 are set on the same plane.

  The nitride film 47 covers the surfaces and side surfaces of the wirings 41, 43, 45 and the oxide film 33. However, the nitride film 47 has holes 47a, 47b, and 47c, and the surfaces of the wirings 41, 43, and 45 are selectively exposed in each of them. FIG. 2 shows a state in which the support portion 23b is connected to the wiring 45 through the hole 47c.

  The edge 45a of the surface of the wiring 45 defines the width on the surface in the direction in which the wiring 45 extends (in FIG. 2, the direction perpendicular to the paper surface). The hole 47c enters the inside of the wiring 45 by a predetermined distance d2 from the edge 45a. Similarly, the support portion 25a and the support portion 23b are connected to the wires 41 and 45 through the holes 47a and 47b, respectively. The wiring 41 is formed so as to be widely exposed below the sensor unit 3.

  As described above, since the direction of the residual stress differs between the oxide film 33 and the nitride film 47, a shear stress acts between them. However, the end of the nitride film 47 forms a hole 47c and is adjacent to the wiring 45 at a predetermined distance d1. Therefore, generation | occurrence | production of peeling can be suppressed.

  Further, as shown in FIG. 2, it is desirable that the support portion 23b covers the hole 47c. More specifically, the support portion 23b is provided so as to be wider than the hole portion 47c by a predetermined distance d2. By connecting the support portion 23b to both the nitride film 47 and the wiring 45, the possibility of peeling between the oxide film 33 provided with the wiring 45 and the nitride film 47 is reduced. In addition, the thick support part 23b also increases the strength of the fixing structure 23.

  3 to 9 are cross-sectional views showing a method of manufacturing the semiconductor acceleration sensor 101 in the order of steps, and show a cross section at a position corresponding to the position AA in FIG.

  First, a substrate body 31 is prepared, and an oxide film 33 is formed thereon. For example, the substrate body 31 is formed using silicon as a semiconductor, and the oxide film 33 is formed by thermal oxidation of the substrate body 31. The wirings 41, 43, and 45 can be formed by the following processes, for example. First, a recess is provided in the oxide film 33 in a region where the wirings 41, 43, and 45 are to be formed. A conductive material having a thickness approximately equal to the depth of the recess, for example, doped polysilicon, is formed and patterned to be narrower than the width of the recess. By these processes, the remaining doped polysilicon becomes wirings 41, 43, 45, and these are selectively formed on the oxide film 33. Next, a nitride film 47 is formed on the oxide film 33 and the wirings 41, 43, and 45 to obtain the structure shown in FIG. However, since the wiring 41 does not exist at the position AA, the wiring 41 does not appear in FIGS. The sacrificial film 51 is formed using, for example, an oxide film, a PSG (phospho silicate glass) film, or a BPSG (boro-phospho silicate glass) film.

  Next, the nitride film 47 is selectively removed by etching, and a hole 47c is formed in the nitride film 47 to obtain the structure shown in FIG. The hole 47c covers the edge 45a on the surface of the wiring 45 with a predetermined distance d1. The holes 47a and 47b can be formed in the same manner.

  Subsequently, a sacrificial film 51 is formed on the surface of the wiring 45 exposed through the hole 47c and on the nitride film 47, and the structure shown in FIG. 5 is obtained. The sacrificial film 51 is formed using, for example, an oxide film, a PSG (phospho silicate glass) film, or a BPSG (boro-phospho silicate glass) film.

  Subsequently, the sacrificial film 51 is etched at positions where the support portions 25a and 23b are to be formed, and selectively removed to form openings 51a that expose the surfaces of the wirings 41, 43, and 45 ( FIG. 6). Since the support portion 23b to be connected to the wiring 45 is formed at the position AA, the opening 51a is formed above the wiring 45 instead of above the wiring 43 in FIG. The opening 51a opens away from the hole 47c by a predetermined distance d2. The opening 51a and the hole 47c form an anchor hole 52 through which the wiring 45 is exposed. Anchor holes are similarly formed in the holes 47a and 47b.

  Dry etching can be employed for the etching of the sacrificial film 51. In that case, it is desirable to use isotropic etching in combination. This is because the angularity on the opening side of the opening 51a can be eliminated as shown in FIG. The advantages of this process will be described later.

  FIG. 10 is a plan view of the vicinity of the anchor hole 52 shown in FIG. 7 as viewed from the opening side of the anchor hole 52.

  Subsequently, as shown in FIG. 8, a thin film layer 53 is formed on the remaining sacrificial film 51 and on the substrate 1 exposed through the anchor hole 52. For example, the thin film layer 53 is thicker than the sacrificial film 51. In this case, the anchor hole 52 is filled with the thin film layer 53.

  Subsequently, as shown in FIG. 9, the thin film layer 53 is selectively removed and patterned. Through this process, the remaining portion of the thin film layer 53 forms the mass body 21, the beam 25, and the fixed electrode 23. For this purpose, the thin film layer 53 is formed using a conductive material, such as doped polysilicon. Speaking in accordance with FIG. 8, the portion of the thin film layer 53 fitted in the anchor hole 52 serves as the support portion 23b, and the portion of the thin film layer 53 located on the sacrificial film 51 forms the fixed electrode portion 23a. Become. The support portion 25a, the mass body 21, the spring portion 25c, and the coupling portion 25b are similarly formed from the thin film layer 53.

  Thereafter, the sacrificial film 51 is removed, and the structure shown in FIGS. 1 and 2 is obtained. If the thin film layer 53 is formed while the sacrificial film 51 is in the shape shown in FIG. 6, a thin portion of the thin film layer 53 is formed near the opening 51a. Such a thin portion is undesirable because it may lead to insufficient strength of the fixing structure 23. Therefore, as shown in FIG. 7, it is desirable to eliminate the angularity on the opening side of the opening 51 a so that even if the thin film layer 53 is formed, a portion having a thin film thickness does not occur.

  In the electrode structure shown in FIG. 9, since the hole 47c covers the wiring 45 at a predetermined distance d1 from the edge 45a, the etchant used for the etching of the sacrificial film 51 performed thereafter is transferred to the oxide film 33. The infiltration path can be taken for a long time. Therefore, the possibility that the etchant reaches the oxide film 33 is reduced. That is, even if the oxide film 33 and the sacrificial film 51 are made of the same silicon oxide film, the possibility that the oxide film 33 is etched in the etching of the sacrificial film 51 is low.

  The thin film layer 53 fills the hole 47c. Therefore, the etchant used for etching the sacrificial film 51 is more effectively prevented from entering the oxide film 33.

  The opening 51a opens away from the hole 47c by a predetermined distance d2, and the thin film layer 53 also fills the opening 51a. By filling the anchor hole 52 with the thin film layer 53 in this way, a longer path for the etchant used to etch the sacrificial film 51 into the oxide film 33 is taken. Moreover, the support part 23b becomes thick and the strength of the fixing structure 23 is increased.

B. Embodiment 2. FIG.
In the present embodiment, a desirable shape in plan view of the hole 47c and the opening 51a will be described. FIG. 11 is a plan view showing an example. Similarly to the structure shown in FIG. 10 of the first embodiment, a hole 47c is provided by entering from the edge 45a by a predetermined distance d1, and an opening 51a is provided by retreating by a predetermined distance d2 from the hole 47c. It has been.

  What is characteristic in the present embodiment is that the hole 47c has a substantially square shape in plan view, but its corner 47r is rounded. The shear stress formed by the residual stress of the oxide film 33 and the residual stress of the nitride film 47 is likely to be concentrated at the corner of the hole 47 c opened in the nitride film 47. However, as in the present embodiment, the shape of the hole 47c in plan view is a polygon with rounded corners, thereby reducing stress concentration.

  The shape of the hole 47c in plan view may be not only a square with rounded corners but also a polygon with rounded corners. The greater the number of rounded corners, the easier the stress concentration is relaxed. Alternatively, as shown in FIG. 12, the shape of the hole 47c in plan view may be an ellipse (including a circle). In this case, the outline of the hole 47c closest to the edge 45a only needs to be separated by a predetermined distance d1.

  FIG. 13 is a plan view showing another example. Similarly to the structure shown in FIG. 10 of the first embodiment, a hole 47c is provided by entering from the edge 45a by a predetermined distance d1, and an opening 51a is provided by retreating by a predetermined distance d2 from the hole 47c. It has been.

  However, in the configuration shown in FIG. 13, the opening 51a has a substantially square shape in plan view, but the corner 51r is rounded. Therefore, also in this case, stress concentration can be relaxed. Although FIG. 13 shows that not only the opening 51a but also the corner 47r of the hole 47c is rounded, only the corner 51r of the opening 51a may be rounded. Similarly to the hole 47c, the shape of the opening 51a in plan view may be not only a square with rounded corners, but also a polygon with rounded corners, or an ellipse (including a circle). Good.

  In the first and second embodiments, the case where the predetermined distance d2 is larger than the predetermined distance d1 is illustrated, but the effect of the present invention can be obtained even if there is a relationship of 0 <d2 <d1. It is obvious.

  Although the present invention has been described in detail, the above description is illustrative in all aspects, and the present invention is not limited thereto. It is understood that countless variations that are not illustrated can be envisaged without departing from the scope of the present invention.

Claims (6)

Wiring (45) selectively disposed on the first insulating film (33);
A hole (47c) that covers the first insulating film and enters the inside of the wiring by a first predetermined distance (d1) from an edge (45a) of the surface of the wiring to selectively expose the surface of the wiring. And a second insulating film (47) that selectively covers the wiring and has a direction of residual stress different from that of the first insulating film,
A support portion (23b) connected to a surface of the wiring selectively exposed through the hole portion and a surface of the second insulating film extending from the hole portion by a second predetermined distance (d2) ; Bei example a conductive thin film structure to have a said second insulating film and a floating portion spaced a predetermined distance and is supported (23a) by the support unit,
In the electrode connection structure, the support portion exhibits a polygon or an ellipse with rounded corners (51r) in plan view in a region connected to the surface of the second insulating film .   The electrode structure according to claim 1, wherein the support portion (23b) covers the hole portion (47c).   The electrode structure according to claim 1, wherein the residual stress of the first insulating film (33) is a compressive stress, and the residual stress of the second insulating film is a tensile stress.   The electrode structure according to claim 3, wherein the first insulating film (33) is an oxide film, and the second insulating film is a nitride film.   The electrode structure according to claim 1, wherein a surface of the first insulating film and a surface of the wiring are on the same plane.   The electrode structure according to claim 1, wherein the hole (47c) has a polygonal shape or an elliptical shape with rounded corners (47r) in plan view.

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