JP2004317478A - Semiconductor acceleration sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a stress, and to provide excellent impact resistance, even when vibration or the like is applied onto a beam at excessive acceleration. <P>SOLUTION: This sensor is provided with a silicon film 3 with the beam 3b drawn out from the central part 3a to be connected to a frame body part 3c, and constituted in an opening part 3d with a stopper 3e laid in an edge part 3da over from the opening part 3d to the frame body part 3c, a silicon oxide film 4 constituted with a suspension part 4a formed on an underface of the central part 3a, a cavity part 4b for surrounding the suspension part 4a, and a frame body part 4c formed on an under face of the frame body part 3c outside the cavity part 4b, a silicon substrate 5 constituted with a mass part 5a of which the each upper face of each mass body applied with force by the acceleration is exposed from the opening part 3d, and of which the one portion in the upper face is engaged with an underface of the suspension part 4a to be suspended, and a support part 5b with the mass bodies stored in its inside with a fixed cavity, in an underface of the frame body part 4c. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a three-axis semiconductor acceleration sensor used for, for example, automobiles, aircraft, home appliances, and the like, and capable of detecting accelerations in X-axis, Y-axis, and Z-axis directions.

2. Description of the Related Art Conventionally, there has been known a semiconductor acceleration sensor that forms a piezo resistor by diffusing impurities on a semiconductor substrate and detects an acceleration applied to the semiconductor substrate by a change in the resistance value of the piezo resistor. As shown in FIGS. 11 and 12, among such sensors, an SOI (Silicon On Insulator) in which a SiO ₂ film (silicon oxide film) 4 and a Si substrate 5 are sequentially formed below a Si (silicon) film 3 is provided. ) Some substrates are processed. More specifically, the Si film 3 has a piezoresistor R formed at the upper end thereof, a flat central portion 3a formed at the central portion thereof, and a beam 3b from the central portion 3a. Is led out and connected to the frame 3c to form an opening 3d surrounded by the beam 3b and the frame 3c.

In the SiO ₂ film 4, a suspending portion 4a is formed according to the lower surface shape of the central portion 3a, and a void portion 4b is formed so as to surround the suspending portion 4a. , A frame portion 4c. In addition, a part of the upper surface of the Si substrate 5 is suspended by engaging with the suspension part 4a, and the mass part 5a receiving a force due to acceleration and the mass part 5a via the suspension part 4a and the like. A supporting portion 5b for supporting is formed (for example, refer to Patent Literature 1 and Patent Literature 2 as related technologies). Then, the glass substrate 2 ′ and the support portion 5b are fixed with the adhesive B, and a semiconductor acceleration sensor is configured.

In a semiconductor acceleration sensor, a mass part and a diaphragm are formed in a cantilever shape, and a stopper for regulating a movable range of the mass part is provided (for example, see Patent Document 3). There are known ones in which a damage detection conductor is provided at an expected location (for example, see Patent Document 4), and one in which an etching solution introduction hole is provided in the beam 3b (for example, see Patent Document 5).
JP-A-6-148229 (page 3-4, FIG. 2) JP-A-7-234242 (pages 2-4, FIG. 2, FIG. 6) JP-A-5-126843 (pages 2-3, FIG. 1, FIG. 11) JP-A-61-178664 (pages 1-3, FIG. 1) JP-A-11-135804 (pages 7-8, FIG. 9, FIG. 10, FIG. 13, FIG. 14)

  Meanwhile, in the semiconductor acceleration sensor shown in FIGS. 11 and 12, when acceleration is applied to the sensor, the mass portion 5a receives a force, and the beam 3b supporting the mass portion 5a is deformed. Since the resistance value of the piezo resistor R formed at the upper end of 3b changes, the target acceleration is detected by converting the resistance value into a voltage value or the like. However, since the beam 3b is formed in a thin shape, if the beam 3b is deformed beyond a certain level due to excessive acceleration, the beam 3b may be damaged and may not function as an acceleration sensor.

  More specifically, when the mass portion 5a is displaced downward, the lower end of the mass portion 5a contacts the glass substrate 2 'to serve as a stopper, thereby preventing the beam 3b from being damaged. However, when the mass portion 5a is displaced upward, there is no longer anything that comes into contact with the mass portion 5a, so that excessive acceleration is applied and the beam 3b is deformed beyond a certain level. Then, the beam 3b may be damaged. In addition, since there is no restriction on the deformation on the upper side, when the mass portion 5a swings largely upward and then returns downward by reaction, the mass portion 5a collides with the rigid glass substrate 2 ′. The beam 3b may be damaged by the mechanical impact.

  The present invention has been made in view of the above-described problems, and has as its object to reduce the stress even if excessive acceleration occurs and mechanical vibration or impact is applied to the beam. And to provide a semiconductor acceleration sensor having excellent shock resistance.

  In order to provide such a semiconductor acceleration sensor, the inventors of the present application derive a beam from four sides in the center, connect the beam to the frame, and form four beams surrounded by the beam and the frame. A silicon film in which an opening and a stopper configured to bridge the edge of the opening and the frame body in each of the openings,

  A suspending portion formed on the lower surface of the central portion, and a cavity formed to surround the suspending portion, and a frame formed on the lower surface of the silicon film frame outside the cavity. A silicon oxide film having a body part,

  An upper surface of each of the four mass bodies subjected to the force due to the acceleration is exposed from the opening through the gap, and a part of the upper surface is engaged with the lower surface of the suspension unit and suspended. A silicon substrate on the lower surface of the frame portion of the silicon oxide film, a silicon substrate having a support portion in which the mass body is stored with a certain gap therein, and (Claim 1).

  In addition, the invention proposes that the center of the stopper is located on the center of gravity of the mass body (claim 2).

  In addition, the invention proposes that the stopper is provided with an impurity diffusion wiring or a stopper breakage detection wiring made of aluminum on the stopper (claim 3).

  Further, using an SOI substrate in which a silicon oxide film and a silicon film are sequentially formed on a silicon substrate, a photoresist is applied on the silicon film, and an opening for introducing an etching gas into the photoresist by photolithography is formed. Formed, anisotropically etching the silicon film by RIE to form a beam on the silicon film from which the beam is led out from the four central portions and connected thereto, and surrounded by the beam and the frame portion. After forming four openings and a stopper that bridges the periphery of the openings,

  An etching solution is injected from the opening, and a portion exposed from the opening and at least a silicon oxide film present at a lower portion of the beam are isotropically etched, and a silicon oxide film is formed on a lower surface of the central portion. Forming a suspension portion to be formed, a gap surrounding the suspension portion, and further forming a frame portion formed on the lower surface of the frame portion of the silicon film outside the gap portion. A proposed manufacturing method has been proposed (claim 4).

  Further, using an SOI substrate in which a silicon oxide film and a silicon film are sequentially formed on a silicon substrate, a photoresist is applied on the silicon film, and an opening for introducing an etching gas into the photoresist by photolithography is formed. Formed, anisotropically etching the silicon film and the silicon oxide film by RIE,

  A frame is connected to the silicon film through which a beam is led out from four sides in the center, four openings formed by being surrounded by the beam and the frame, and a peripheral portion of the opening is bridged. While forming a stopper to pass,

  In the silicon oxide film, a suspending portion formed on the lower surface of the central portion, a part of a void formed to surround the suspending portion, and a silicon film frame outside the void. After forming the frame formed on the lower surface of the body,

  After forming a photoresist so as to cover at least a part of the suspension part and the side surface part of the silicon oxide film frame part, an etching solution is injected from the opening, and at least the silicon oxide existing under the beam is formed. A manufacturing method is proposed in which a film is isotropically etched to form a void in a silicon oxide film (claim 5).

  Further, according to the manufacturing method corresponding to the above-described claim 4, at the time of the anisotropic etching, after forming an opening for introducing an etching gas into the photoresist, the etching by the RIE is performed. A manufacturing method is proposed in which an etching solution introduction hole is formed in the stopper, and thereafter the isotropic etching is performed (claim 6).

  As described above, according to the first aspect of the present invention, even if excessive acceleration is generated and mechanical vibration or impact is applied to the beam, the stress is reduced and the beam is excellent in impact resistance. It works.

  According to the second aspect of the invention, there is an effect that noise can be reduced without picking up sensitivity in the rotation direction and sensitivity characteristics can be improved.

  According to the third aspect of the present invention, when the stopper is broken, the breakage can be detected, so that the beam can be prevented from being broken.

  According to the fourth aspect of the invention, it is possible to form a stopper on the silicon film.

  According to the fifth aspect of the invention, there is an effect that side etching of the silicon oxide film can be minimized when the stopper is formed.

  According to the invention of claim 6, there is an effect that even if the width of the stopper is large, the silicon oxide film under the stopper can be quickly removed.

  The above-described solution will be described in detail below as a specific embodiment. First, the structure and the like of the semiconductor acceleration sensor of the present application will be described, and then the manufacturing method thereof will be described in detail.

[First Embodiment]
1 and 2 are views showing a semiconductor acceleration sensor according to a first embodiment of the present application. FIG. 1 is a perspective view of the sensor, FIG. 2 is a top view (a) of the sensor, and FIG. FIG. 3B is a cross-sectional view of FIG. As shown in FIG. 1, the semiconductor acceleration sensor has a substantially cubic shape or a substantially rectangular box shape, and is configured by joining a lower surface portion of an SOI substrate 1 and an upper surface portion of a glass substrate 2 to each other. As an example, the SOI substrate 1 has a Si film 3 having a thickness of about several μm to 10 μm, an SiO ₂ film 4 having a thickness of about 0.3 to 1 μm formed on the lower surface thereof, and further formed on the lower surface thereof. And a Si substrate 5 having a thickness of about 300 to 600 μm.

  The glass substrate 2 is glass containing mobile ions such as Pyrex (registered trademark) glass, and is to be bonded to glass or Si by anodic bonding. A piezoresistor R is formed at the upper end of the Si film 3 (disposition will be described later), and a central portion 3a of a rectangular flat plate shape is formed at the central portion thereof. A substantially rectangular flat beam 3b is led out from the center (four sides) of each of the four sides, and is connected to a frame (a silicon film frame) 3c formed in a square shape in a vertical view.

  A stopper 3e is formed in each of the four openings 3d formed by being surrounded by the beam 3b and the frame 3c so as to bridge the inside of the edge 3da between the opening 3d and the frame 3c. Have been. Specifically, a stopper 3e having a rectangular shape in cross section as viewed in the longitudinal direction is formed so as to bridge two orthogonal sides near the four corners of the frame portion 3c.

The SiO ₂ film 4 has a rectangular flat plate-shaped suspending portion 4a formed in a central portion thereof in accordance with the lower surface shape of the central portion 3a, and a void portion 4b is formed so as to surround the suspending portion 4a. Further, a rectangular frame portion (frame portion of a silicon oxide film) 4c having a rectangular shape in a vertical view is formed outside the gap portion 4b in accordance with the lower surface shape of the frame portion 3c. The Si substrate 5 includes a mass part 5a that receives a force due to acceleration applied to the semiconductor acceleration sensor, and a support part 5b for supporting the mass part 5a via a suspension part 4a or the like.

  The mass portion 5a is composed of four substantially cubic masses, each of which has an upper surface exposed from the opening 3d through the gap 4b, and one end (fourth corner) of the four corners of the upper surface. A part) is engaged with the lower surface of the suspension part 4a and suspended in a state of being suspended in the air, while the support part 5b is formed of a rectangular frame in a vertical view according to the lower surface shape of the frame part 4c. The mass is stored with a certain gap therein. With the above-described configuration, even when the mass portion 5a moves upward, the lower end of the stopper 3e abuts on the upper end of the mass portion 5a, so that the beam 3b is more than a certain value. The beam 3b can be prevented from being damaged without being deformed.

  Further, as shown in FIG. 2A, the portions where the lateral end portions of the central portion 3a are connected to the beam 3b are respectively arranged in the longitudinal direction so as to be parallel to the longitudinal direction of the beam 3b. , Piezoresistors Rx1, Rx2, Rx3, Rx4 for detecting acceleration in the X-axis direction are formed. Similarly, in the portion where the beam 3b is connected to both ends in the vertical direction of the central portion 3a, the acceleration in the Y-axis direction is detected in the horizontal direction so as to be parallel to the longitudinal direction of the beam 3b. Piezoresistors Ry1, Ry2, Ry3, and Ry4 are formed.

  Further, a piezoresistor for detecting acceleration in the Z-axis direction is provided at a portion where both ends in the vertical direction of the frame 3c are connected to the beam 3b so as to be parallel to the longitudinal direction of the beam 3b. Rz1 and Rz4 are formed. Similarly, accelerations in the Z-axis direction are applied to the portions where the lateral inner ends of the frame 3c are connected to the beam 3b so as to be perpendicular to the longitudinal direction of the beam 3b. Piezo resistors Rz2 and Rx3 to be detected are formed.

  Note that these piezoresistors are formed by impurity diffusion wirings, are connected to a pattern formed by the impurity diffusion wirings, and further, contact windows are formed at predetermined positions on the pattern to be connected to aluminum wirings. (Patterns and the like are not shown). Although the pattern or the aluminum wiring forms a Wheatstone bridge circuit, the details of the circuit are omitted because they are based on JP-A-6-331646.

[Second embodiment]
Next, a semiconductor acceleration sensor according to a second embodiment will be described with reference to FIG. FIG. 3 is a top view of the semiconductor acceleration sensor. The semiconductor acceleration sensor of the present embodiment is different from the above-described basic structure in that the stopper 3e has a feature that the stopper 3e is vertically bent at a center portion thereof, and the center portion hits the center of gravity of the mass portion 5a (mass body). This is the point configured. The sensitivity characteristics can be improved by doing in this way. The reason is as follows.

  When a large downward acceleration is applied to the acceleration sensor, the upper end of the mass portion 5a comes into contact with the lower end of the stopper 3e. At this time, the stopper 3e is located far from the center of gravity of the mass portion 5a. If there is, the beam 3b is easily distorted due to the moment of inertia applied to the mass portion 5a around the contact portion, and a twist is generated. For this reason, the sensitivity in the rotation direction is also picked up and noise is increased, and the sensitivity characteristics of each of the X, Y, and Z axes are reduced. Therefore, sensitivity characteristics can be improved by adopting the above-described configuration so that the moment of inertia does not occur.

[Third Embodiment]
Next, a semiconductor acceleration sensor according to a third embodiment will be described with reference to FIG. FIG. 4 is a top view of the semiconductor acceleration sensor. The semiconductor acceleration sensor of the present embodiment is different from the above-described basic structure in that the stopper 3e is provided with a frame body in the opening 3d so that the corner 5aa of the mass 5a is covered and hidden in plan view. 3c is formed in a region near a corner formed by two adjacent sides of 3c. That is, a flat plate having a triangular shape in a plan view is formed in a region near a corner formed by two sides of the frame portion 3c. As described above, by increasing the connecting portion between the stopper 3e and the frame portion 3c, the breaking strength of the stopper 3e can be improved.

  Note that the shape of the stopper 3e in plan view is not limited to a triangle, and may be changed as appropriate within the scope of the present invention, such as a square or a fan. Further, it is preferable that the area is large in a range where the stopper 3e does not contact the beam 3b.

[Fourth embodiment]
Next, a structure for detecting that the stopper 3e has been damaged will be described in detail with reference to FIG. FIG. 5 is a top view of the semiconductor acceleration sensor. The semiconductor acceleration sensor according to the present embodiment is different from the above-described basic structure in that an impurity diffusion wiring or a stopper break detection wiring 6 made of aluminum is formed on the stopper 3e, and both ends of the wiring 6 are provided at both ends, respectively. The pad 7 for electrically connecting to the outside is connected, and the pad 7 is provided near the both ends in the lateral direction of the frame 3c. Hereinafter, features of the configuration will be described.

The above-described stopper 3e has an effect of absorbing an impact due to excessive acceleration due to its flexibility. However, even if excessive acceleration is applied, the stopper 3e is damaged by a collision (excessive displacement) of the mass portion 5a. Subsequently, the beam 3b having a width or thickness greater than that of the stopper 3e is damaged. Therefore, if the damage can be detected at the stage where the stopper 3e is damaged, the damage of the beam 3b can be prevented. Further, even when the stopper 3e and the beam 3b are simultaneously damaged, it is possible to detect the failure. Although the structure and the like have been described above, an SiO ₂ film and a Si ₃ N ₄ film are sequentially formed on the Si film 3 so that impurities do not enter the Si film 3 (not shown). ).

[Method of manufacturing semiconductor acceleration sensor]
Next, a method for manufacturing the semiconductor acceleration sensor according to the present invention will be described in detail with reference to FIGS. 1 and 2 and FIGS. 6 and 7 are views showing the respective manufacturing steps, and are cross-sectional views taken along the line BB 'shown in FIG. First, a photoresist 8 is applied on the SOI substrate 1 formed by SIMOX (Silicon Implanted Oxide) or a bonding method. Then, an opening window 8a for introducing impurities is formed by photolithography in order to form a piezoresistor at the above-described predetermined position.

  More specifically, an opening window 8a is formed by placing a photomask on the upper surface of the photoresist 8 and irradiating ultraviolet rays to expose a predetermined portion of the photoresist 8, and then applying a developing solution. You. After the opening window 8a is formed, an impurity is introduced by thermal diffusion or ion implantation (boron may be deposited by diffusion) to form an impurity diffusion wiring 9 serving as a piezoresistance (see FIG. 6A). ). Although not particularly shown, the stopper breakage detection wiring 6 can be formed in the same manner as the impurity diffusion wiring 9.

Then, after removing the remaining photoresist 8 by applying a removing solution such as HNO ₃ , the SiO ₂ film 10 is formed by a CVD (Chemical Vapor Deposition) method using a source gas of SiH 4 + O 2 at 400 ° C. or less. Then, a Si ₃ N ₄ film 11 is formed thereon by a CVD method using a source gas of SiH 4 + 4NH 3 at 900 ° C. or lower (see FIG. 6B). Thereby, while the difference in expansion coefficient between the Si film 3 and the Si ₃ N ₄ film 11 is absorbed by the SiO ₂ film 10, the Si ₃ N ₄ film 11 can serve as a barrier to impurities, that is, a passivation.

Next, a photoresist 12 is applied on the Si ₃ N ₄ film 11 and a photomask is formed to form predetermined shapes (central portion 3a, beam 3b, frame portion 3c, opening 3d, stopper 3e). To form an opening 12a for introducing an etching gas. Then, the Si ₃ N ₄ film 11, the SiO ₂ film 10, and the Si film 3 are anisotropically etched according to a pattern by RIE (Reactive Ion Etching) using CF ₄ as an etching gas (see FIG. 6C). ). In the etching, a dielectric coupling plasma type (ICP) may be used.

Next, the remaining photoresist 12 is removed with a removing solution, and an etching solution such as hydrofluoric acid or a mixed solution of hydrofluoric acid is injected through the opening 3d to expose the portion exposed from the opening 3d and the beam 3b and the beam 3b. The SiO ₂ film present under the stopper 3e is isotropically etched to form a void 4b (see FIG. 7A). Then, a photoresist is applied to the lower surface of the mass portion 5a, exposure and development are performed using a photomask, and anisotropic etching is performed by RIE while leaving the photoresist 12a only at the lower end of the support portion 5b. Thereafter, a photoresist is applied to the etched portion, and anisotropic etching is performed by RIE while leaving the photoresist 12b on the lower surface of the mass part 5a (see FIG. 7B).

  Next, the photoresists 12a and 12b are removed with a removing solution, and the support 5b is placed on the glass substrate 2. Then, the support portion 5b is set to have a positive potential, and a voltage of 200 V to 1000V is applied between the glass substrate 2 and the support portion 5b to raise the temperature of the glass substrate 2 and the support portion 5b to around 450 ° C. Let it. By doing so, the cations contained in the glass substrate 2 are attracted to the negative potential and reach the surface layer of the glass substrate 2, while a large amount of negative ions remain in the glass substrate 2 and Since the space charge layer is formed at the junction with the portion 5b, a strong attractive force is generated between the glass substrate 2 and the supporting portion 5b, and the coupling is completed (see FIG. 7C).

[Method of securing oxide film thickness]
By the way, in the above-described manufacturing method, when the SiO ₂ film existing under the beam 3b and the stopper 3e shown in FIG. 4a and the frame portion 4c are side-etched, and the strength is reduced. To prevent this, the following manufacturing method may be adopted. First, at the time of etching the Si ₃ N ₄ film 11 and the like shown in FIG. 6C, the etching is performed up to the SiO ₂ film 4 so as to cover at least the side surfaces of the suspension 4a and the frame 4c. Then, a photoresist 14 is formed (see FIG. 8A).

Next, a mixed solution of hydrofluoric acid or the like is injected from the opening 3d, and the portion exposed from the opening 3d and the SiO ₂ film present under the beam 3b and the stopper 3e are isotropically etched to form a gap. The part 4b is formed. At this time, since all of the side surfaces of the frame portion 4c and most of the suspension portions 4a are covered with the photoresist 14, it is difficult to perform side etching by isotropy of a hydrofluoric acid mixed solution or the like. Absent.

  However, the connection between the suspension portion 4a and the beam 3b is side-etched, but the periphery of the suspension portion 4a is not side-etched as in the above-described manufacturing method. (See FIG. 8B). Next, the photoresist 14 is removed with a removing liquid, and the mass part 5a and the support part 5b shown in FIG. 7B are formed, and the photoresist 14 and the glass substrate 2 shown in FIG. Just connect.

[Etching method of stopper lower part]
In the above-described manufacturing method, when the width of the stopper 3e is large, it takes time to remove the SiO ₂ film 4 thereunder. In order to prevent this, as shown in FIG. 9A, an etching solution introduction hole 3ea may be provided in the stopper 3e. Specifically, in the above-described manufacturing method, an opening 12b for introducing an etching gas into the photoresist 12 is also formed at the time of etching the Si ₃ N ₄ film 11 and the like shown in FIG. I do. Then, as described above, the etching solution introduction hole 3ea can be formed by etching by RIE (see FIG. 9B).

By doing so, even if the width of the stopper 3e is large, the SiO ₂ film 4 thereunder can be easily etched. The SiO ₂ film 4 below the beam 3b may be etched from below when forming the mass part 5a and the support part 5b. The opening 12b is formed in a square shape or a circular shape in a vertical view, and may be formed not only in a configuration in which a plurality of holes are arranged in a line as shown in FIG.

[How to make the stopper thinner]
Further, in the above-described stopper damage detection structure, it is desired that the stopper 3e be damaged before the beam 3b when an excessive acceleration is applied. For that purpose, it is necessary to reduce the strength, that is, it is necessary that the stopper 3e is thinner than the beam 3b. Here, the method of thinning will be described in detail with reference to FIG. FIG. 10 is a view showing a state after the manufacturing process of FIG. 7B has been completed and the photoresists 12a and 12b have been removed, and is an upside-down view.

To reduce the thickness of the stopper, first, before joining the glass substrate 2 and the support portion 5b, an SiO ₂ film 13 or the like is formed on the surface of the semiconductor acceleration sensor by CVD, and a protective film from etching is formed. At this time, since the stopper 3e is located below the mass part 5a, the SiO ₂ film 13 does not adhere to the surface of the stopper 3e as compared with the surface of the mass part 5a.

Therefore, the stopper 3e is thinned by removing the SiO ₂ film 13 accumulated on the stopper 3e with a hydrofluoric acid mixed solution (see FIG. 10A) and performing isotropic etching with TMAH or KOH. (See FIG. 10B). Then, the SiO ₂ film 13 on the upper surfaces of the mass part 5a and the support part 5b may be removed by etching to join the glass substrate 2.

FIG. 2 is a perspective view showing a structure of the semiconductor acceleration sensor according to the first embodiment of the present invention, and is a partially cutaway view showing an internal structure. It is a figure which shows the structure of a semiconductor acceleration sensor same as the above, (a) and (b) are a top view and a sectional view of A-A 'in the top view, respectively. It is a top view showing the structure of the semiconductor acceleration sensor concerning a 2nd embodiment of the present invention. It is a top view showing the structure of the semiconductor acceleration sensor concerning a 3rd embodiment of the present invention. It is a top view showing the structure of the semiconductor acceleration sensor concerning a 4th embodiment of the present invention. FIG. 4 is a diagram showing each manufacturing process of the semiconductor acceleration sensor of the present invention, and is a cross-sectional view taken along line B-B ′ in the top view of FIG. 2. FIG. 4 is a diagram showing each manufacturing process of the semiconductor acceleration sensor of the present invention, and is a cross-sectional view taken along line B-B ′ in the top view of FIG. 2. It is a figure which shows the manufacturing method for preventing reduction of reinforcement by side etching, (a), (b) is a top view and sectional drawing, respectively. It is a figure which shows the etching method of a stopper lower part, (a), (b) is a top view and sectional drawing, respectively. It is a figure showing a manufacturing method for thinning a stopper. FIG. 9 is a perspective view showing a structure of a conventional semiconductor acceleration sensor, partially cut away to show an internal structure. It is a figure which shows the structure of the conventional semiconductor acceleration sensor, (a), (b) is a top view, and sectional drawing of A-A 'in the top view, respectively.

Explanation of reference numerals

Reference Signs List 1 SOI substrate 3 Silicon film 3a Central part 3b Beam 3c Frame part (silicon film frame part)
3d opening 3da edge 3e stopper 3ea etching solution introduction hole 4 silicon oxide film 4a hanging portion 4b gap 4c frame (frame of silicon oxide)
Reference Signs List 5 silicon substrate 5a mass part 5b support part 12 photoresist 12a opening 14 photoresist

Claims (6)

The beam is led out from the four sides of the central portion and connected to the frame portion, and four openings formed by being surrounded by the beam and the frame portion, and the openings and the frame are respectively provided in those openings. A silicon film configured with a stopper that bridges the inside of the edge with the body,
A suspending portion formed on the lower surface of the central portion, and a cavity formed to surround the suspending portion, and a frame formed on the lower surface of the silicon film frame outside the cavity. A silicon oxide film having a body part,
An upper surface of each of the four mass bodies subjected to the force due to the acceleration is exposed from the opening through the gap, and a part of the upper surface is engaged with the lower surface of the suspension unit and suspended. A silicon substrate having a support portion on the lower surface of the silicon oxide film frame portion, the support portion storing the mass body with a certain gap therein. 2. The semiconductor acceleration sensor according to claim 1, wherein a center portion of the stopper is on a center line of the mass body. 2. The semiconductor acceleration sensor according to claim 1, wherein the stopper has an impurity diffusion wiring or a stopper breakage detection wiring made of aluminum formed thereon. Using an SOI substrate in which a silicon oxide film and a silicon film are sequentially formed on a silicon substrate, a photoresist is applied on the silicon film, and an opening for introducing an etching gas into the photoresist is formed by photolithography. , The silicon film is anisotropically etched by RIE, and a beam is formed on the silicon film by being surrounded by the beam portion and the frame portion, from which beams are led out from four sides in the center. After forming one opening and a stopper that spans the periphery of the opening,
An etching solution is injected from the opening, and a portion exposed from the opening and at least a silicon oxide film present at a lower portion of the beam are isotropically etched, and a silicon oxide film is formed on a lower surface of the central portion. Forming a suspension portion to be formed, a gap surrounding the suspension portion, and further forming a frame portion formed on the lower surface of the frame portion of the silicon film outside the gap portion. Of manufacturing a semiconductor acceleration sensor. Using an SOI substrate in which a silicon oxide film and a silicon film are sequentially formed on a silicon substrate, a photoresist is applied on the silicon film, and an opening for introducing an etching gas into the photoresist is formed by photolithography. The silicon film and the silicon oxide film are anisotropically etched by RIE,
A frame is connected to the silicon film through which a beam is led out from four sides in the center, four openings formed by being surrounded by the beam and the frame, and a peripheral portion of the opening is bridged. While forming a stopper to pass,
In the silicon oxide film, a suspending portion formed on the lower surface of the central portion, a part of a void formed to surround the suspending portion, and a silicon film frame outside the void. After forming the frame formed on the lower surface of the body,
After forming a photoresist so as to cover at least a part of the suspension part and the side surface part of the silicon oxide film frame part, an etching solution is injected from the opening, and at least the silicon oxide existing under the beam is formed. A method of manufacturing a semiconductor acceleration sensor, wherein a film is isotropically etched to form a void in a silicon oxide film. At the time of the anisotropic etching, an opening for introducing an etching gas is also formed in the photoresist, and then the etching by the RIE is performed to form an etching solution introduction hole in the stopper. The method according to claim 4, wherein isotropic etching is performed.

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