JP2011038781A - Semiconductor device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device capable of stabilizing electric potential of a substrate without complicating a structure, and to provide a method of manufacturing the same. <P>SOLUTION: The semiconductor device includes: a semiconductor substrate 10 of a single-crystal structure on whose upper surface a recess 100 is formed; a beam-shaped movable part 20 which includes a movable electrode 21 disposed in the recess 100 and having a lower insulating film 50 disposed on a lower surface, and is fixed to the semiconductor substrate 10 at a position spaced apart from the movable electrode 21; a beam-shaped stationary electrode 30 disposed in the recess 100 so as to face the movable electrode 21 and fixed to the semiconductor substrate 10; an insulating isolation film 40 which is disposed between the movable and stationary electrodes 20, 30 and the semiconductor substrate 10, and electrically isolates the movable and stationary electrodes 21, 30 from the substrate 10; and a contact electrode 63 connected to the substrate 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a semiconductor device having a beam-shaped movable portion and a method for manufacturing the semiconductor device.

  2. Description of the Related Art A MEMS (Micro Electro Mechanical System) device having a movable portion that is displaced according to an externally applied force (hereinafter referred to as “external force”) is used as a sensor for detecting a physical quantity such as an acceleration sensor or a gyro sensor. ing. For example, a capacitive acceleration sensor that detects acceleration by detecting a change in capacitance between a movable electrode and a fixed electrode that vibrates due to an external force has been put to practical use.

  In order to form a beam-shaped movable portion, a stacked body such as an SOI substrate in which an insulating film layer and a semiconductor layer are stacked on a semiconductor substrate is used (for example, see Patent Document 1). A part of the semiconductor layer is used as a movable part, and the insulating film layer is used as a sacrificial layer.

JP-A-2005-342808

  However, a sensor that detects a minute change in electrostatic capacitance is likely to malfunction due to the influence of noise. For this reason, it is necessary to stabilize the potential of the substrate. For example, the substrate is grounded. Therefore, when a laminated body in which an insulating film layer and a semiconductor layer are stacked on a semiconductor substrate is used, it is necessary to ground the semiconductor substrate and the semiconductor layer at two locations, and grounding electrodes are provided on the upper side and the lower side of the semiconductor device. Must be placed. As a result, there is a problem that the structure of the semiconductor device is complicated.

  In view of the above problems, an object of the present invention is to provide a semiconductor device and a method for manufacturing the semiconductor device that can stabilize the potential of the substrate without complicating the structure.

  According to one aspect of the present invention, (a) a semiconductor substrate having a single crystal structure having a recess formed on the upper surface, and (b) a movable substrate disposed in the recess and having a lower surface insulating film disposed on the lower surface. A beam-type movable part having an electrode and fixed to the semiconductor substrate at a position away from the movable electrode, and (c) a beam-type fixed part disposed in the recess facing the movable electrode and fixed to the semiconductor substrate. (D) an isolation insulating film that is disposed between the movable part and the fixed electrode and the semiconductor substrate and electrically separates the movable electrode and the fixed electrode from the semiconductor substrate; and (e) a contact connected to the semiconductor substrate. A semiconductor device comprising an electrode is provided.

  According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device having a movable part having a movable electrode and a fixed electrode fixed to the semiconductor substrate so as to face the movable electrode, and (B) forming a first recess by etching a part of the upper surface; (b) forming an isolation insulating film on the sidewall of the first recess and a lower insulating film on the bottom; Forming a buried semiconductor film on the isolation insulating film and the lower insulating film and filling the first recess with the buried semiconductor film; and (d) etching a part of the buried semiconductor film to form the movable portion and the fixed electrode. A step of forming a side surface groove in which the side surface is exposed; (e) a step of forming a side surface insulating film on the side surface of the movable portion and the fixed electrode exposed in the side surface groove; and (f) a lower surface insulating film exposed on the bottom surface of the side surface groove. And steps to remove ( Forming a second recess in a part of the upper portion of the semiconductor substrate by etching using the side surface insulating film and the lower surface insulating film as a mask, and separating the lower surface of the movable portion and the fixed electrode from the semiconductor substrate. A manufacturing method is provided.

  According to the present invention, it is possible to provide a semiconductor device and a semiconductor device manufacturing method capable of stabilizing the potential of the substrate without complicating the structure.

It is a typical top view showing the composition of the semiconductor device concerning the embodiment of the present invention. It is sectional drawing along the II-II direction of the semiconductor device shown in FIG. FIG. 3 is a cross-sectional view taken along the III-III direction of the semiconductor device shown in FIG. 1. FIG. 4 is a cross-sectional view of the semiconductor device shown in FIG. 1 along the IV-IV direction. FIG. 2 is a perspective view of a region A of the semiconductor device shown in FIG. It is process drawing for demonstrating the manufacturing method of the semiconductor device which concerns on embodiment of this invention (the 1). It is process drawing for demonstrating the manufacturing method of the semiconductor device which concerns on embodiment of this invention (the 2). It is process drawing for demonstrating the manufacturing method of the semiconductor device which concerns on embodiment of this invention (the 3). It is process drawing for demonstrating the manufacturing method of the semiconductor device which concerns on embodiment of this invention (the 4). It is process drawing for demonstrating the manufacturing method of the semiconductor device which concerns on embodiment of this invention (the 5). It is process drawing for demonstrating the manufacturing method of the semiconductor device which concerns on embodiment of this invention (the 6). It is process drawing for demonstrating the manufacturing method of the semiconductor device which concerns on embodiment of this invention (the 7). It is process drawing for demonstrating the manufacturing method of the semiconductor device which concerns on embodiment of this invention (the 8). It is process drawing for demonstrating the manufacturing method of the semiconductor device which concerns on embodiment of this invention (the 9). It is process drawing for demonstrating the manufacturing method of the semiconductor device which concerns on embodiment of this invention (the 10). It is process drawing for demonstrating the manufacturing method of the semiconductor device which concerns on embodiment of this invention (the 11). It is typical sectional drawing which shows the example which has arrange | positioned the cover to the semiconductor device which concerns on embodiment of this invention. It is typical sectional drawing which shows the example of the board | substrate of the semiconductor device which concerns on embodiment of this invention. It is typical sectional drawing which shows the shape of the movable part of the semiconductor device which concerns on related technology.

  Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, and arrangement of components. Etc. are not specified below. The technical idea of the present invention can be variously modified within the scope of the claims.

  As shown in FIG. 1, a semiconductor device according to an embodiment of the present invention includes a semiconductor substrate 10 having a single crystal structure having a recess 100 formed on the upper surface, and a lower insulating film disposed on the lower surface. 50, a movable electrode 20 having a beam shape, which is fixed to the semiconductor substrate 10 at a position spaced from the movable electrode 21, and disposed in the recess 100 so as to face the movable electrode 21, A beam-shaped fixed electrode 30 fixed to the substrate 10 and the movable portion 20 and the fixed electrode 30 are disposed between the semiconductor substrate 10 and electrically isolate the movable electrode 21 and the fixed electrode 30 from the semiconductor substrate 10. An isolation insulating film 40 and a contact electrode 63 connected to the semiconductor substrate 10 are provided.

  As shown in FIGS. 2 and 3, the recess 100 is at the same height as the movable portion 20 and the fixed electrode 30, and the first region surrounded by the isolation insulating film 40 and the first region It consists of the 2nd area | region which is below and the semiconductor substrate 10 was exposed to the side surface. Although details will be described later, the first region is a region formed as the side surface groove 500, and the second region is the second recess 120 formed by isotropic etching of the semiconductor substrate 10.

  As shown in FIGS. 2, 3, and 5, the isolation insulating film 40 is formed on the sidewall of the recess 100, and the isolation insulating film 40 is disposed so as to surround the recess 100.

  As shown in FIG. 1, the movable portion 20 includes a central stripe portion 22, a plurality of movable electrodes 21 extending in a direction perpendicular to the direction in which the central stripe portion 22 extends from the central stripe portion 22, and the central stripe portion and the semiconductor substrate 10. Is a beam-type vibrator having a fishbone structure. The spring portion 23 is fixed to the semiconductor substrate 10 via the isolation insulating film 40.

  As shown in FIG. 2, a lower surface insulating film 50 is disposed on the lower surface of the movable portion 20. Further, a side insulating film 52 is disposed on the side surface of the movable portion 20, and an upper surface insulating film 54 is disposed on the upper surface, and the entire periphery of the movable portion 20 is covered with the insulating film.

  The fixed electrode 30 is a beam-type vibrator having a fixed end fixed to the semiconductor substrate 10 and a free end extending into the recess 100 at a peripheral portion surrounding the recess 100. As shown in FIGS. 1 and 3, the fixed electrode 30 is fixed to the semiconductor substrate 10 via an isolation insulating film 40. As shown in FIGS. 2 and 3, a lower insulating film 50 is disposed on the lower surface of the fixed electrode 30, a side insulating film 52 is disposed on the side surface, and an upper insulating film 54 is disposed on the upper surface, so that the entire periphery of the fixed electrode 30 is an insulating film. Covered with.

  As described above, the movable portion 20 and the fixed electrode 30 are fixed to the semiconductor substrate 10 via the isolation insulating film 40. The movable electrode 21 and the fixed electrode 30 are electrically separated by the separation insulating film 40. Therefore, the movable electrode 21 and the fixed electrode 30 function as a capacitor plate.

  The position of the movable portion 20 changes according to the external force applied to the semiconductor device from the outside, and the distance between the movable electrode 21 and the fixed electrode 30 changes. Therefore, when an external force is applied to the semiconductor device with a voltage applied between the movable electrode 21 and the fixed electrode 30, a change in the distance between the movable electrode 21 and the fixed electrode 30 is detected as a change in capacitance. The semiconductor device transmits the detected change in capacitance to a signal processing circuit (not shown) as a detection signal. The signal processing circuit processes the detection signal to detect acceleration generated in the semiconductor device. That is, the semiconductor device shown in FIG. 1 is a part of a capacitance type acceleration sensor that detects acceleration based on a change in capacitance between the movable electrode 21 and the fixed electrode 30. The signal processing circuit may be arranged on the same chip as the semiconductor device, or may be arranged on a different chip from the chip on which the semiconductor device is arranged.

  As shown in FIG. 1, the movable portion 20 and the semiconductor substrate 10 are connected by a spring-shaped spring portion 23 having flexibility, so that the movable portion 20 is easily vibrated. Thereby, the detection sensitivity of the semiconductor device is improved.

  In the semiconductor device shown in FIG. 1, the electrode wiring 61 for transmitting the voltage value of the movable electrode 21 to the signal processing circuit is the same as the movable portion 20 in the opening 610 formed by removing a part of the upper surface insulating film 54. Connecting. On the other hand, the electrode wiring 62 for transmitting the voltage value of the fixed electrode 30 to the signal processing circuit is connected to the fixed electrode 30 in the opening 620 formed by removing a part of the upper surface insulating film 54.

  As shown in FIG. 1, the movable electrode 21 and the fixed electrode 30 are arranged in a crossed finger shape. Thereby, the area where the movable electrode 21 and the fixed electrode 30 face each other increases, and the capacitance between the movable electrode 21 and the fixed electrode 30 increases. Therefore, acceleration can be detected with high sensitivity. The width of the movable part 20 and the fixed electrode 30 in the region where the movable part 20 and the fixed electrode 30 face each other is, for example, about 3 μm to 10 μm, and the distance between the movable part 20 and the fixed electrode 30 is, for example, about 1 μm to 2 μm. is there.

  As shown in FIG. 1, a contact electrode 63 is disposed on a peripheral region surrounding the recess 100 of the semiconductor substrate 10. As shown in FIG. 4, the contact electrode 63 is connected to the semiconductor substrate 10 in the upper surface insulating film 54 formed on the semiconductor substrate 10 and the opening 630 formed in the surface insulating film 15. Therefore, the potential of the semiconductor substrate 10 can be set using the contact electrode 63 disposed on the upper surface of the semiconductor device.

  For example, the semiconductor substrate 10 can be grounded, so that the potential of the semiconductor substrate 10 is stabilized. As a result, the semiconductor device shown in FIG. 1 can prevent malfunction due to the influence of noise. Further, since the semiconductor substrate 10 is a single crystal structure, the potential of the entire semiconductor substrate 10 can be stabilized by one contact electrode 63. That is, it is not necessary to arrange grounding electrodes on the upper and lower sides of the semiconductor device, and the structure of the semiconductor device is not complicated. Therefore, according to the semiconductor device shown in FIG. 1, the potential of the semiconductor substrate 10 can be stabilized without complicating the structure.

  Although an example in which the contact electrode 63 is disposed on the upper surface of the semiconductor device is shown in FIG. 1, the contact electrode 63 can be disposed on the lower surface, for example, on the lower surface of the semiconductor device.

  A method for manufacturing a semiconductor device according to an embodiment of the present invention will be described with reference to FIGS. The semiconductor device manufacturing method described below is merely an example, and it is needless to say that the present invention can be realized by various other manufacturing methods including this modification.

(A) As shown in FIGS. 6A and 6B, a surface insulating film 15 is formed on the upper surface of the semiconductor substrate 10. For example, a silicon (Si) substrate is used as the semiconductor substrate 10, and a silicon oxide (SiO ₂ ) film having a thickness of about 0.5 μm is formed on the surface insulating film 15 by a thermal oxidation method or a chemical vapor deposition (CVD) method. Form as. 6A is a perspective view, and FIG. 6B is a cross-sectional view (the same applies to FIGS. 7A, 7B to 11A, and 11B).

  (B) Using the photoresist film as an etching mask, a part of the surface insulating film 15 is selectively removed by etching, so that the first recess 110 is formed as shown in FIGS. 7A to 7B. Form. When the semiconductor substrate 10 is a Si substrate, a wet etching method using a hydrofluoric acid-based etchant or the like can be used to form the first recess 110. Alternatively, a dry etching method such as a deep reactive ion etching (D-RIE) method may be used.

(C) An insulating film such as a SiO ₂ film is formed on the surface of the first recess 110 by thermal oxidation, CVD, sputtering, SOG (Spin On Glass) coating, or the like. Alternatively, an insulating film may be formed on the surface of the first recess 110 by providing an oxide film inside the semiconductor substrate 10 using a SIMOX (Separation by Implanted Oxygen) technique in which oxygen is implanted by implantation. Specifically, as shown in FIGS. 8A to 8B, the isolation insulating film 40 is formed on the side wall of the first recess 110, and the lower surface insulating film 50 is formed on the bottom surface. The isolation insulating film 40 and the lower surface insulating film 50 can be formed simultaneously. In that case, the isolation insulating film 40 and the lower insulating film 50 are made of the same material. The isolation insulating film 40 and the lower insulating film 50 are formed in a connected state.

  (D) As shown in FIGS. 9A and 9B, an embedded semiconductor film 700 is formed on the isolation insulating film 40 and the lower insulating film 50, and the first recess 110 is formed by the embedded semiconductor film 700. Embed. For example, a buried semiconductor film 700 is formed by depositing a polysilicon film on the semiconductor substrate 10 by an epitaxial growth method or the like. Thereafter, the upper portion of the embedded semiconductor film 700 is polished by chemical mechanical polishing (CMP) or the like until the surface of the surface insulating film 15 is exposed. Next, as shown in FIGS. 10A and 10B, the upper portion of the embedded semiconductor film 700 is etched back by a thickness d by chemical dry etching (CDE) or the like. The thickness d is, for example, about 0.5 μm to 2.0 μm.

(E) As shown in FIGS. 11A and 11B, an upper surface insulating film 54 having a film thickness of about 0.5 μm to 4.0 μm is formed on the entire surface by CVD or the like. A stacked body of the surface insulating film 15 and the upper surface insulating film 54 is formed on the semiconductor substrate 10, and the upper surface insulating film 54 is formed in the embedded semiconductor film 700. For example, a SiO ₂ film can be used as the upper surface insulating film 54, but the insulating film is not limited to the SiO ₂ film, and may be another insulating film of a single layer or a laminated body in which a plurality of insulating films are stacked. Good. For example, a stacked body in which an insulating film resistant to stress such as a silicon nitride (LP-SiN) film formed by low-pressure formation is disposed on a single oxide film, a thermal oxide film (SiO ₂ film), and an LP-SiN film A laminated body made of a CVD-SiO ₂ film formed by the CVD method can be used for the upper surface insulating film 54.

  (F) For example, the upper surface insulating film 54 is selectively etched by RIE or the like using a photoresist film formed on the upper surface insulating film 54 by photolithography as an etching mask to form the upper surface insulating film 54 in a desired pattern. To do. Specifically, as shown in FIGS. 12A, 12B, and 12C, the embedded semiconductor is left with the upper surface insulating film 54 on the region where the movable portion 20 and the fixed electrode 30 are formed. The top insulating film 54 on the film 700 is removed. 12B is a cross-sectional view taken along the XIIb-XIIb direction of FIG. 12A, and FIG. 12C is a perspective view of the region A of FIG.

  (G) As shown in FIGS. 13A to 13E, using the patterned upper surface insulating film 54 as an etching mask, a part of the embedded semiconductor film 700 is selectively selected until the lower surface insulating film 50 is exposed. Etch into. Thereby, the side surface groove | channel 500 which the side surface of the movable part 20 and the fixed electrode 30 is exposed is formed. The movable portion 20 and the fixed electrode 30 formed from the embedded semiconductor film 700 are connected to the semiconductor substrate 10 via the isolation insulating film 40 formed on the side wall of the first recess 110. For the etching for forming the side groove 500, a Bosch method using a D-RIE method or the like can be employed. 13B is a cross-sectional view along the XIIIb-XIIIb direction of FIG. 13A, FIG. 13C is a cross-sectional view along the XIIIc-XIIIc direction of FIG. 13A, and FIG. 13A is a cross-sectional view taken along the XIIId-XIIId direction in FIG. 13A, and FIG. 13E is a perspective view of the region A in FIG. 13A (FIGS. 14A to 14E to 16). The same applies to (a) to FIG. 16 (e)).

(H) As shown in FIGS. 14A to 14E, the side insulating film 52 is formed on the side surfaces of the movable portion 20 and the fixed electrode 30 exposed in the side groove 500. The side insulating film 52 is an insulating film such as a SiO ₂ film or a SiN film having a thickness of, for example, about 0.1 μm to 0.3 μm. For the formation of the side insulating film 52, a thermal oxidation method or a CVD method can be used. The thinner the side insulating film 52 is, the narrower the distance between the movable part 20 and the fixed electrode 30 can be, and the movable part 20 and the fixed electrode 30 can be arranged with high density. As a result, detection sensitivity can be improved.

  (I) The lower surface insulating film 50 exposed on the bottom surface of the side groove 500 is removed as shown in FIGS. 15A to 15E by, for example, a photolithography technique using a tape resist and anisotropic etching. To do. As a result, the surface of the semiconductor substrate 10 is exposed on the bottom surface of the side groove 500. On the other hand, the lower surface insulating film 50 remains on the lower surfaces of the movable portion 20 and the fixed electrode 30. Simultaneously with the removal of the lower surface insulating film 50, a part of the upper surface insulating film 54 formed on the movable portion 20 and the fixed electrode 30 is removed to form openings 610 and 620. Further, a part of the upper surface insulating film 54 and the surface insulating film 15 formed on the semiconductor substrate 10 is removed, and an opening 630 is formed.

  (N) As shown in FIGS. 16A to 16E, an electrode wiring 61 connected to the movable portion 20 through the opening 610 and an electrode wiring 62 connected to the fixed electrode 30 through the opening 620. The contact electrode 63 connected to the semiconductor substrate 10 through the opening 630 is formed. For example, the electrode wirings 61 and 62 made of a metal film such as an aluminum (Al) film, and the contact are formed by a lift-off method using a photoresist film formed in a desired pattern or an etching method using the photoresist film as an etching mask. An electrode 63 is formed.

(L) The side surface insulating film 52 formed on the side surface of the movable part 20 and the fixed electrode 30 and the lower surface insulating film 50 formed on the lower surface of the movable part 20 and the fixed electrode 30 are used as etching masks. A part of the upper part is etched by isotropic etching to form the second recess 120. By this isotropic etching (hereinafter referred to as “release etching”), the bottom of the movable portion 20 and the fixed electrode 30 and the semiconductor substrate 10 are separated, and the bottom surface disposed on the bottom surfaces of the movable portion 20 and the fixed electrode 30. The insulating film 50 is exposed. That is, the movable portion 20 and the fixed electrode 30 are disposed above the second recess 120 by release etching. For example, when the semiconductor substrate 10 is a silicon substrate, release etching is performed by an isotropic etcher using sulfur hexafluoride (SF ₆ ) or xenon difluoride (XeF ₂ ). Thus, the semiconductor device shown in FIG. 1 is completed. That is, the movable portion 20 and the fixed electrode 30 are disposed in a recess 100 that is formed of the side surface groove 500 and the second recess 120 and formed on the upper surface of the semiconductor substrate 10.

  As described above, according to the method for manufacturing a semiconductor device according to the embodiment of the present invention, the first recess 110 is formed on the upper surface of the semiconductor substrate 10, and the lower insulating film 50 is formed on the first recess 110. After the formation, the first recess 110 is embedded with an embedded semiconductor film 700 for forming the movable portion 20 and the fixed electrode 30. Therefore, there is no complicated process such as a substrate bonding process, and the structure is simple. Further, it is not necessary to employ an SOI substrate including an insulating film layer that is a sacrificial layer, and the semiconductor substrate 10 has a single crystal structure.

  Further, as described with reference to FIG. 10B, the upper surface of the embedded semiconductor film 700 is etched back by the thickness d and becomes lower than the upper surface of the surface insulating film 15. For this reason, as shown in FIG. 17, when the lid 90 is arranged on the upper surface of the semiconductor device, a space is generated between the movable portion 20 and the lid 90, and the lid 90 is not affected even if the movable portion 20 vibrates in the vertical direction. A structure without contact can be realized. The thickness d is set in consideration of the vibration width of the movable part 20 and the like. The lid 90 can employ a plate-like lid made of, for example, glass or silicon. If the upper surface of the embedded semiconductor film 700 is not etched back, the position of the upper surface of the embedded semiconductor film 700 and the position of the upper surface of the surface insulating film 15 coincide. In this case, the upper surface of the movable part 20 and the fixed electrode 30 and the upper surface of the peripheral region of the semiconductor substrate 10 around the recess 100 are at the same plane level.

  In order to fill the first recess 110 with the embedded semiconductor film 700 without a gap, as shown in FIG. 7B, the side wall of the first recess 110 is formed with a taper with respect to the bottom surface. The recess 110 preferably has a wider opening than the bottom. The taper angle formed between the side wall and the bottom surface of the first recess 110 is, for example, about 72 to 85 degrees.

  The depth of the 1st recessed part 110 is set based on the thickness of the movable part 20 or the fixed electrode 30, for example, is about 30 micrometers-about 100 micrometers. Since the detection sensitivity increases as the movable part 20 and the fixed electrode 30 are thicker, the depth of the first recess 110 depends on the desired detection sensitivity. Since the movable portion 20 and the fixed electrode 30 are formed from the embedded semiconductor film 700 embedded in the upper surface of the semiconductor substrate 10, variations in thickness of the movable portion 20 and the fixed electrode 30 can be easily reduced.

The depth of the first recess 110 can be set to a predetermined depth by controlling the etching time. Alternatively, as shown in FIG. 18A, the depth of the first recess 110 may be controlled with higher accuracy by using a semiconductor substrate 10 in which two semiconductor layers having different impurity concentrations are stacked. . For example, a semiconductor substrate 10A having a p-type impurity concentration of about 1 × 10 ¹⁷ cm ⁻³ is stacked on a semiconductor layer 10B having a p-type impurity concentration of about 1 × 10 ¹⁸ to 1 × 10 ²⁰ cm ^−3. 10 is configured. The etching rates of the semiconductor layer 10A and the semiconductor layer 10B are different due to the difference in impurity concentration, and the etching can be almost stopped at the interface between the semiconductor layer 10A and the semiconductor layer 10B. For this reason, as shown in FIG. 18B, the first recess 110 having the depth of the semiconductor layer 10A can be formed. The difference in impurity concentration between the semiconductor layer 10A and the semiconductor layer 10B may be about one digit. As described above, by using the semiconductor substrate 10 in which two semiconductor layers having different impurity concentrations are stacked, the depth of the first recess 110 can be precisely controlled, and the thickness of the movable portion 20 and the fixed electrode 30 can be controlled. The variation of can be reduced.

  Further, in the semiconductor device shown in FIG. 1, a lower surface insulating film 50 is disposed on the lower surfaces of the movable portion 20 and the fixed electrode 30. For this reason, in the release etching, for example, as shown in FIG. 19, the lower surface of the movable portion 20 and the fixed electrode 30 is prevented from being etched. The arrow shown in FIG. 19 is the direction in which etching proceeds. Therefore, by disposing the lower surface insulating film 50 on the lower surfaces of the movable portion 20 and the fixed electrode 30, it is possible to prevent the movable portion 20 and the fixed electrode 30 from becoming thin. As a result, the thickness of the movable part 20 and the fixed electrode 30 does not vary. Furthermore, a decrease in the area where the movable electrode 21 and the fixed electrode 30 face each other is suppressed.

  Therefore, in the semiconductor device shown in FIG. 1 in which the lower surface insulating film 50 is disposed on the lower surfaces of the movable portion 20 and the fixed electrode 30, the detection sensitivity is higher than that of the detection device in which the lower surfaces of the movable portion 20 and the fixed electrode 30 are etched. Will improve. The film thickness of the lower surface insulating film 50 may be such a thickness that the lower surface insulating film 50 is etched in release etching and the lower surfaces of the movable portion 20 and the fixed electrode 30 are not exposed. It is determined by the etching rate difference with the insulating film 50 or the like. The film thickness of the lower surface insulating film 50 is, for example, about 0.5 μm.

  Since the movable part 20 and the fixed electrode 30 have a beam shape, the etchant turns around from the lateral direction (short direction) of the movable part 20 and the fixed electrode 30 during the release etching, and the movable part 20 and the fixed electrode 30 The semiconductor substrate 10 is separated. For this reason, it is not necessary to make the 2nd recessed part 120 deep.

  Since the semiconductor substrate 10 without an insulating film layer is used as described above, the potential of the entire semiconductor substrate 10 can be stabilized by one contact electrode 63, and malfunction due to the influence of noise can be prevented. For example, it is not necessary to arrange grounding electrodes on the upper and lower sides of the semiconductor device. Therefore, according to the method for manufacturing a semiconductor device according to the embodiment of the present invention, it is possible to provide a semiconductor device capable of stabilizing the potential of the substrate without complicating the structure.

  Note that the embedded semiconductor film 700 is embedded not in the entire top surface of the semiconductor device but in a part thereof. For example, when the embedded semiconductor film 700 is a polysilicon film, if the first recess 110 is deepened to make the movable portion 20 and the fixed electrode 30 thick, the influence of the grain size of the polysilicon embedded in the first recess 110 is affected. As a result, the surface of the semiconductor device is roughened. However, in the case of the semiconductor device shown in FIG. 1, an alignment key can be formed on the surface of the semiconductor substrate 10 made of, for example, single crystal silicon, around the recess 100. Since the surface of the alignment portion is not rough, alignment accuracy does not decrease. Therefore, even when the movable part 20 and the fixed electrode 30 are formed thick in order to improve the detection sensitivity, the precision of microfabrication does not decrease.

(Other embodiments)
As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, the present invention is applicable to a multi-axis acceleration sensor that detects not only acceleration in one direction but also acceleration in a plurality of directions. In addition, although an example in which the semiconductor device is an acceleration sensor has been described, the present invention is not limited to an acceleration sensor, and the present invention can be applied to various sensors that detect a physical quantity using a structure that is displaced according to an external force. For example, the present invention can be applied to an angular velocity sensor, a pressure sensor, a force sensor, and the like.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  The semiconductor device of the present invention can be used in the electronic equipment industry including the manufacturing industry that manufactures semiconductor sensors having movable parts.

DESCRIPTION OF SYMBOLS 10 ... Semiconductor substrate 15 ... Surface insulating film 20 ... Movable part 21 ... Movable electrode 22 ... Center stripe part 23 ... Spring part 30 ... Fixed electrode 40 ... Isolation insulating film 50 ... Lower surface insulating film 52 ... Side surface insulating film 54 ... Upper surface insulating film 61, 62 ... electrode wiring 63 ... contact electrode 90 ... lid 100 ... recess 110 ... first recess 120 ... second recess 500 ... side groove 610, 620, 630 ... opening 700 ... buried semiconductor film

Claims (13)

A semiconductor substrate of a single crystal structure having a recess formed on the upper surface;
A movable electrode having a movable electrode disposed in the recess and having a lower surface insulating film disposed on the lower surface, and fixed to the semiconductor substrate at a position spaced apart from the movable electrode;
A beam-shaped fixed electrode disposed in the recess facing the movable electrode and fixed to the semiconductor substrate;
An isolation insulating film disposed between the movable part and the fixed electrode and the semiconductor substrate, and electrically separating the movable electrode and the fixed electrode from the semiconductor substrate;
And a contact electrode connected to the semiconductor substrate.   The semiconductor device according to claim 1, wherein the isolation insulating film is disposed on a sidewall of the recess so as to surround the recess.   The semiconductor device according to claim 1, wherein the isolation insulating film and the lower surface insulating film are made of the same material.   The semiconductor device according to claim 1, wherein the isolation insulating film and the lower surface insulating film are connected to each other.   The semiconductor device according to claim 1, wherein the contact electrode is disposed on a peripheral region of the semiconductor substrate surrounding the recess.   The semiconductor device according to claim 1, wherein the movable electrode and the fixed electrode are arranged in a crossed finger shape.   The semiconductor device according to claim 1, wherein a connection portion of the movable portion with the semiconductor substrate is a spring shape. A method for manufacturing a semiconductor device, comprising: a movable part having a movable electrode; and a fixed electrode fixed to a semiconductor substrate facing the movable electrode,
Etching a part of the upper surface of the semiconductor substrate to form a first recess;
Forming a separation insulating film on the side wall of the first recess and a lower surface insulating film on the bottom surface;
Forming a buried semiconductor film on the isolation insulating film and the bottom insulating film, and embedding the first recess with the buried semiconductor film;
Etching a part of the embedded semiconductor film to form a side groove in which side surfaces of the movable part and the fixed electrode are exposed;
Forming a side surface insulating film on the side surface of the movable part exposed to the side surface groove and the fixed electrode;
Removing the lower surface insulating film exposed at the bottom of the side groove;
A second recess is formed in a part of the upper portion of the semiconductor substrate by etching using the side surface insulating film and the lower surface insulating film as a mask, and the lower surface of the movable part and the fixed electrode is separated from the semiconductor substrate. A method for manufacturing a semiconductor device comprising the steps of:   9. The method of manufacturing a semiconductor device according to claim 8, further comprising a step of etching back an upper portion of the embedded semiconductor film.   10. The manufacturing method of a semiconductor device according to claim 8, wherein a part of the embedded semiconductor film is etched using an upper surface insulating film disposed on the embedded semiconductor film as a mask to form the side groove. Method. Removing a part of the upper surface insulating film formed on the movable part and the fixed electrode to form an opening;
The method for manufacturing a semiconductor device according to claim 10, further comprising: forming, on the upper surface insulating film, electrode wirings respectively connected to the movable part or the fixed electrode in the opening. Removing a part of the upper surface insulating film formed on the semiconductor substrate to form an opening;
The method for manufacturing a semiconductor device according to claim 10, further comprising: forming a contact electrode connected to the semiconductor substrate at the opening on the upper surface insulating film.   13. The semiconductor device according to claim 11, wherein the opening is formed by removing a part of the upper surface insulating film simultaneously with the removal of the lower surface insulating film exposed on the bottom surface of the side surface groove. Production method.

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