JP2005345245A - Capacitance type dynamic quantity sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitance type dynamic quantity sensor and its manufacturing method expected to effectively use a chip size and shorten design time. <P>SOLUTION: By forming a plurality of through holes in part of beams and weights in the capacitance type dynamic quantity sensor, the time required for designing mechanical characteristics is shortened to facilitate designs for compact formation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a capacitive mechanical quantity sensor that detects mechanical physical quantities such as acceleration and angular velocity as capacitance changes. In particular, the present invention relates to a capacitive mechanical quantity sensor manufactured by a semiconductor manufacturing process.

  Conventionally, a weight that is displaced by acceleration or angular velocity applied from the outside and a beam that supports the weight are formed in a semiconductor substrate, and the capacitance change between the movable electrode of the weight and a fixed electrode that is formed at a minute interval. A capacitance type mechanical quantity sensor to detect is known (for example, refer to Patent Document 1).

  FIG. 8 shows a schematic diagram thereof. In this sensor, a weight 81 and a beam 82 are fabricated in a semiconductor substrate 83 by fine processing, and are bonded and sealed from both sides with glass substrates (upper substrate 84 and lower substrate 85). The weight 81 is supported by the beam 82 in a minute space formed by the upper substrate 84, the lower substrate 85, and the semiconductor substrate 83, and is in a floating state.

  When a physical quantity (for example, acceleration) is applied to such a sensor from the outside, a force proportional to the physical quantity is applied to the weight 81 having mass, and the weight 81 is displaced by the bending of the beam 82. Thereby, the capacitance value between the fixed electrode 86 formed on the glass and the movable electrode made of the weight 81 changes, and the magnitude of the added physical quantity can be measured.

Here, mechanical characteristics (resonance frequency, spring constant) that greatly affect the sensitivity characteristics of the sensor greatly depend on the sizes of the weight 81 and the beam 82. In particular, in the vibration type angular velocity sensor, in order to show good sensitivity characteristics, the resonance frequency in the direction perpendicular to the beam surface (here defined as Z direction) and the beam longitudinal direction (here defined as X direction) It is required to form the resonance frequency within an error range of several percent (for example, see Non-Patent Document 1).
JP-A-8-94666 “Design Guidelines for Vibration Type Micro Gyro” Maechu et al., IEEJ Transactions E, Vol. 118-E, no. 7/8, pp. 377-383 (1998)

  However, the sensor structure shown in Japanese Patent Laid-Open No. 8-94666 has a structure in which the vibrations in the Z direction and the X direction do not move independently but move in conjunction with each other. That is, when the resonance frequency in the X direction is changed, the resonance frequency in the Z direction is also changed. Therefore, when adjusting the size of the beam or the weight in order to keep the resonance frequency in the Z direction within the specified range, the resonance frequency in the X direction is out of the specification, and the resonance frequency in the X direction is within the specification. When trying to fit in, the resonance frequency in the Z direction often deviates from the specification. By repeating this calculation several times, it is possible to keep both the X and Z resonance frequencies within the specifications, and the design time is longer than necessary. In addition, in order to keep both the X and Z resonance frequencies within the specifications, it may be unavoidable to increase the size of the weight and beam, which increases the chip size and increases the cost.

The present invention has been made in view of the above problems, and is a capacitive mechanical quantity sensor that detects a change in capacitance caused by displacement of a structure manufactured using a semiconductor process, such as a mechanical physical quantity such as acceleration and angular velocity. ,
A semiconductor substrate having a weight supported by a beam and displaced by a mechanical quantity such as acceleration or angular velocity applied from the outside and a part of the surface of the semiconductor substrate are joined, and a minute gap 1 is arranged at a position opposite to the weight. The upper glass substrate on which the fixed electrode 1 is laminated, and the lower glass substrate on which the fixed electrode 2 is laminated with a minute gap 2 at a position opposed to the weight and bonded to a part of the back surface of the semiconductor substrate. In the capacitive mechanical quantity sensor for measuring the mechanical quantity from the change in capacitance between the movable electrode made of the weight and the fixed electrode 1 and the change in capacity between the movable electrode made of the weight and the fixed electrode 2 due to the displacement of the weight, A capacitive mechanical quantity sensor, wherein a through hole is formed in a part of a weight.

  A capacitive mechanical quantity sensor, wherein a plurality of through holes are formed.

  Therefore, by forming through holes in the beam and the weight, it is possible to adjust the mechanical characteristics such as the resonance frequency and the spring constant without changing the size of the beam and the weight, and without trouble, and the design time Can be expected to shorten. In addition, the degree of freedom in adjusting the beam and weight size can be increased, and the sensor formation region can be used effectively.

  Also, a step of forming recesses on both sides of the semiconductor substrate, a step of processing the inside of the recesses on the surface of the semiconductor substrate, a step of forming a through hole in the beam and a part of the beam, and a processing of the inside of the recess on the back surface of the semiconductor substrate. A step of forming a through-hole in a weight supported by a beam and a part of the weight, a step of forming a fixed electrode 1 on the surface of a flat upper glass substrate, and a step of fixing to the surface of a flat lower glass substrate The upper glass substrate is bonded to the surface of the semiconductor substrate so that the fixed electrode 1 is disposed at the position where the electrode 2 is laminated and the weight is opposed, and the fixed electrode 2 is disposed at the position where the weight is opposed. And a step of joining the lower glass substrate to the back surface of the semiconductor substrate.

  Further, a semiconductor substrate having a weight supported by a beam and displaced by a mechanical quantity such as acceleration or angular velocity applied from the outside, and a part of the surface of the semiconductor substrate are joined, and a minute gap 1 is provided at a position opposite to the weight. The upper glass substrate on which the fixed electrodes 1 are stacked, and the lower glass substrate on which the fixed electrodes 2 are bonded to a part of the back surface of the semiconductor substrate and spaced apart by a minute gap 2 at a position facing the weight. In the capacitive mechanical quantity sensor that measures the mechanical quantity from the change in capacitance between the movable electrode made of the weight and the fixed electrode 1 and the change in capacity between the movable electrode made of the weight and the fixed electrode 2 due to the displacement of the weight, In manufacturing a capacitive dynamic quantity sensor characterized in that a through hole is formed in a part of the beam, the through hole formed in the beam and a part of the beam is formed by the same etching process. Features Method of manufacturing a capacitive dynamic quantity sensor.

  Further, a semiconductor substrate having a weight supported by a beam and displaced by a mechanical quantity such as acceleration or angular velocity applied from the outside, and a part of the surface of the semiconductor substrate are joined, and a minute gap 1 is provided at a position opposite to the weight. The upper glass substrate on which the fixed electrodes 1 are stacked, and the lower glass substrate on which the fixed electrodes 2 are bonded to a part of the back surface of the semiconductor substrate and spaced apart by a minute gap 2 at a position facing the weight. In the capacitive mechanical quantity sensor that measures the mechanical quantity from the change in capacitance between the movable electrode made of the weight and the fixed electrode 1 and the change in capacity between the movable electrode made of the weight and the fixed electrode 2 due to the displacement of the weight, In manufacturing a capacitive dynamic quantity sensor characterized in that a through hole is formed in a part of a beam, the weight and the through hole formed in a part of the weight are formed by the same etching process. Features Method of manufacturing a capacitive dynamic quantity sensor.

  Therefore, the number of processes can be reduced by reducing the number of steps by reducing the number of steps by processing the through holes formed in the beam and a part of the beam, or the through holes formed in the weight and a part of the weight in the same process. Can also be improved.

  By forming through-holes in the beam and weight, it is possible to expect a reduction in adjustment time in the design of mechanical characteristics such as resonance frequency and spring constant, and a reduction in development costs can be expected. In addition, since there is a degree of freedom in adjusting the beam and weight sizes, it is possible to effectively use the sensor formation region and prevent the sensor size from being increased.

  Hereinafter, an angular velocity sensor will be taken as an example of the mechanical quantity sensor of the present invention and will be described in detail with reference to the accompanying drawings.

  First, FIG. 1 shows a cross-sectional view of a capacitive mechanical quantity sensor according to Embodiment 1 of the present invention. This mechanical quantity sensor has a three-layer structure of an upper glass substrate 1, a silicon substrate 2 and a lower glass substrate 3, and these three substrates are joined to produce a structure. A vibrating body having a beam 4 and a weight 5 is formed in the semiconductor (silicon) substrate 2 by etching, and the vibrating body (the beam 4 and the weight 5) is vibrated or twisted by a force applied from the outside. Or The thickness, width, and length of the beam 4 and the thickness, area, and the like of the weight 5 are designed so that an arbitrary spring constant and resonance frequency can be obtained. Further, there are minute gaps 6 and 7 between the beam 4 and the weight 5 formed on the semiconductor substrate 2 and the upper and lower glass substrates 1 and 3 facing each other. The vibrator (beam 4 and weight 5) is connected to the outer periphery of the semiconductor substrate 2 via the beam 4. The beam 4 that supports the weight 5 is bent by the force from the outside, and the weight 5 moves in the minute gaps 6 and 7.

  Through holes 8 are formed in a part of the upper and lower glass substrates 1 and 3 sandwiching the silicon substrate 2 on which the vibrating body (the beam 4 and the weight 5) is formed from above and below, and through these through holes 8, the upper and lower glasses 1 and 3 are formed. The structure is such that the electrode formed on the inside is pulled out to the outside. A conductive material 9 is laminated outside the through hole 8, and the inside of the glass (the minute gaps 6 and 7) is sealed. The fixed electrode 11 formed inside the upper and lower glass substrates 1 and 3 is taken out from the conductive material 9 through the wiring formed on the side wall of the through hole 8. Note that a through hole 12 for adjusting the resonance frequency and the spring constant of the vibrating body is formed in a part of the beam 4 and the weight 5.

  Here, the capacitive mechanical quantity sensor according to the first embodiment operates on the same principle as the sensor described in, for example, Japanese Patent Laid-Open No. 10-227644. Here, the operation principle will be briefly described below. An AC voltage is applied to the excitation fixed electrode 10 provided on the inner surface side of the upper glass substrate 1 and the lower glass substrate 3, and a vibrating body (beam 4 and weight 5) serving as a movable electrode held at the ground (ground). The vibrating body (beam 4 and weight 5) is vibrated up and down by an electrostatic force acting between them. When an angular velocity around the y-axis is applied to the vibrating body (beam 4 and weight 5) given velocity in the z-axis direction in this way, the Coriolis force of their vector product is given in the x-axis direction. As shown, the beam 4 bends. On the inner surface side of the upper glass substrate 1 and the lower glass substrate 3, a fixed electrode for detection 11 is provided. From the inclination of the weight 5 due to the bending of the beam 4, the fixed electrode 11 for detection and the weight 5 serving as a movable electrode, A change occurs in the capacity between the two, and the magnitude of the angular velocity is detected from this change in capacity.

FIG. 3 shows an example of a plan view of the capacitive mechanical quantity sensor according to the first embodiment of the present invention. The weight 31 is supported by beams 32 from four directions, and the end portions 34, 35, 36, and 37 of the beams 32 are fixed to the outer peripheral portion of the semiconductor substrate 2 in FIG. Both the weight 31 and the beam 32 are basically vertically and horizontally symmetrical. The spring constant k indicating the mechanical characteristics of such a vibrating body is represented by k = nEbt ³ / L ² , and the resonance frequency f is represented by f = 1 / 2π · √k / m (n beam number, E Young's modulus, (t beam thickness, b beam thickness, L beam length, m weight mass). In the sensor shown in FIG. 3, several through holes 33 are regularly formed in the beam 32 for the purpose of adjusting the resonance frequency and the spring constant of the vibrating body. By adjusting the size and number of the through holes 33, arbitrary resonance frequencies and spring constants in the X, Y, and Z axes are obtained. Such an adjustment mechanism facilitates the design and can be expected to shorten the design time. For example, when it is desired to decrease the resonance frequency and the spring constant, the number of through holes 33 is increased or the size is increased. When the resonance frequency and the spring constant are desired to be increased, the number of the through holes 33 is decreased or the size is decreased. Further, as shown in FIG. 4A, for example, even when the size of the beam 42 is designed to be smaller than the size of the weight 41, the through hole 44 is formed in the beam 43 as shown in FIG. By inserting, the size of the weight 45 and the size of the beam 43 can be adjusted to approximately the same level. In the normal design, in order to obtain the target mechanical characteristics, the length and width of the beam are changed. However, the sensor size may increase, leading to an increase in cost. According to the capacitive dynamic quantity sensor according to the first embodiment of the present invention, it is possible to expect a reduction in design time through easy adjustment, and it is possible to effectively utilize the sensor formation region.

  When the resonance frequency of Z and the resonance frequency of X and Y are increased or decreased to the same extent, it is possible by the correspondence shown in FIGS. 3 and 4, but the resonance frequency of Z and the resonance frequency of X and Y If there is a difference between the increase amount and the decrease amount, the adjustment method shown in FIG. 5 is effective. When the resonance frequencies in the X and Y directions are designed to be lower than the target specification, it is effective to form a through hole 52 toward the end of the weight 51 as shown in FIG. Although the resonance frequency of Z is slightly increased, the effect of increasing the resonance frequencies of X and Y is greater than that. By reducing the outer mass, the moment in the X and Y directions applied to the center of gravity of the weight can be reduced, and the resonance frequencies in the X and Y directions can be effectively increased. Similarly, even in the case where the resonance frequency in the Z direction is designed to be lower than the target specification, as shown in FIG. On the other hand, the resonance frequency of Z can be efficiently increased by the method of forming the through hole 54.

As described above, the method shown in FIGS. 3 to 5 can deal with the resonance frequency and the spring constant in the Z direction, the X and Y directions within the target specification, and without increasing the sensor size.
Here, in FIG. 3 to FIG. 5, the shape of the through hole is shown as a cylinder. However, the shape of the through hole is not limited to this and may be a polygonal column such as a triangular note or an elliptical column. In addition, since the formation of the through hole can be simultaneously formed by etching used in the step of forming the beam and the step of forming the weight, the cost is not increased.

  6 and 7 are diagrams illustrating the manufacturing process of the angular velocity sensor according to the first embodiment of the present invention. First, as shown at 601 in FIG. 6, etching masks 62 are formed on both surfaces of the silicon substrate 61 by photolithography. Although silicon oxide or silicon nitride is used for the mask material, other materials can be used as long as they are resistant to the etchant of silicon. In the case of an oxide film, the mask material can be easily etched with hydrofluoric acid, and a mask pattern can be produced. Further, an SOI (Silicon On Insulator) substrate in which an oxide film is embedded may be used as the substrate. In this case, since the intermediate oxide film functions as an etch stop layer in beam processing or weight processing, high-precision processing is realized with respect to thickness.

  Next, as shown at 602 in FIG. 6, the silicon substrate 61 is etched from both sides to form the recesses 63 and 64 for minute gaps. The etchant used here is, for example, an anisotropic etchant such as a tetramethylammonium hydroxide aqueous solution or a potassium hydroxide aqueous solution so as to obtain a highly accurate minute gap. When etching is completed, the etching mask is peeled off with boiling acid or the like. In this etching step 602, the dents 63 and 64 may of course be formed by dry etching such as reactive ion etching. In that case, the etching mask 62 can be made of a material that can withstand dry etching, such as a resist.

  Next, as shown by reference numeral 603 in FIG. 6, the shape of the beam 65 and a part 66 of the through hole are simultaneously formed by processing from the surface side by dry etching such as reactive ion etching or inductively coupled plasma (ICP) etching. . For the etching mask material, silicon oxide or silicon nitride may be used, or a resist may be used. By using a high-density plasma process using ICP or electron cyclotron, vertical processing is possible, and the etching rate is improved, which improves the vibration characteristics of the beam and reduces the manufacturing cost.

Next, the silicon substrate 61 is etched from the back side by a high-density plasma process, and the shape of the weight 67 and the through hole 68 are simultaneously formed. At this time, a part of the substrate is penetrated to form a vibrating body (beam 65 and weight 67).
In addition, when an SOI substrate is used, an intermediate oxide film remains, but the vibrator is formed by etching the intermediate oxide film thereafter.

  Next, FIG. 7 is a diagram illustrating a manufacturing process of the upper glass substrate and the lower glass substrate. Since the upper glass substrate and the lower glass substrate have the same structure, they will be described with reference to the same drawing.

  First, as shown at 701 in FIG. 7, a glass substrate 71 having a through hole 73 and a high impurity concentration silicon substrate 72 are prepared. As the glass, glass having the same thermal expansion coefficient as that of silicon is selected, and the through hole 73 is formed by blasting or the like.

  Next, as shown at 702 in FIG. 7, after the glass substrate 71 (the surface side with the smaller hole diameter) and the high impurity concentration silicon substrate 72 are joined, the high impurity concentration silicon substrate 72 is thinly cut by polishing.

  Next, as indicated by reference numeral 703 in FIG. 7, the high impurity concentration silicon 72 is etched to form the outer wiring 74 of the upper glass substrate and the lower glass substrate. This etching may be dry or wet.

  Next, as shown by 704 in FIG. 7, the inner wiring 75 is formed by laminating the metal film from the surface side where the hole diameter of the through hole is large and forming a pattern. Thereafter, heat treatment is performed to secure a potential contact with the outer wiring 74.

Finally, although not shown in the drawing, the upper glass substrate, the silicon substrate, and the lower glass substrate manufactured by the processes as shown in FIGS. 6 and 7 are joined, the structure is sealed, and the sensor as shown in FIG. Create the structure. Bonding at this time uses anodic bonding in which a cathode voltage is applied to the glass side and electrostatic attraction between the glass and silicon is utilized, or eutectic bonding in which metals are laminated and bonded to the bonding surface.
In the angular velocity sensor manufactured by such a process, the number of processing steps is reduced by processing the through hole formed in the beam and a part of the beam and the through hole formed in the weight and a part of the weight in the same process. And cost reduction effect can be obtained.
In the description of the first embodiment, the angular velocity sensor is taken as an example. However, the first embodiment can be applied to an acceleration sensor and a force sensor that form similar beams and weights.

1 is a cross-sectional view of a capacitive dynamic quantity sensor according to Embodiment 1. FIG. 1 is a cross-sectional view of a capacitive dynamic quantity sensor according to Embodiment 1. FIG. 1 is an example of a plan view of a capacitive dynamic quantity sensor according to Embodiment 1. FIG. 1 is an example of a plan view of a capacitive dynamic quantity sensor according to Embodiment 1. FIG. 1 is an example of a plan view of a capacitive dynamic quantity sensor according to Embodiment 1. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the capacitive dynamic quantity sensor according to Embodiment 1. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the capacitive dynamic quantity sensor according to Embodiment 1. FIG. It is sectional drawing explaining the conventional capacitive mechanical quantity sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper glass substrate 2 Silicon substrate 3 Lower glass substrate 4 Beam 5 Weight 6, 7 Minute clearance 8 Through hole 9 Conductive material 10 Excitation fixed electrode 11 Detection fixed electrode 12 Through hole 31, 41, 45, 51, 53 Weight 32, 42, 43 Beams 33, 44, 52, 54 Through holes 34, 35, 36, 37 Ends 61 of the beam 61 Silicon substrate 62 Etching masks 63, 64 Recess 65 Beam 66 Part of the through hole 67 Weight 68 Through hole 71 Glass substrate 72 High impurity concentration silicon substrate 73 Through hole 74 Outer wiring 75 Inner wiring 81 Weight 82 Beam 83 Semiconductor substrate 84 Upper substrate 85 Lower substrate 86 Fixed electrode

Claims (5)

A semiconductor substrate having a weight which is supported by a beam and which is displaced by a mechanical quantity composed of acceleration or angular velocity applied from the outside;
An upper glass substrate that is bonded to a part of the surface of the semiconductor substrate and in which a fixed electrode 1 is disposed at a position opposed to the weight with a minute gap 1 therebetween;
A lower glass substrate formed by laminating a fixed electrode 2 bonded to a part of the back surface of the semiconductor substrate and arranged with a minute gap 2 at a position opposed to the weight;
A capacitive mechanical quantity sensor that measures the mechanical quantity from a change in capacitance between the movable electrode made of the weight and the fixed electrode 1 and a change in capacitance between the movable electrode made of the weight and the fixed electrode 2 due to the displacement of the weight. In
A capacitive mechanical quantity sensor, wherein a through-hole is formed in a part of the beam and the weight.   The capacitive mechanical quantity sensor according to claim 1, wherein a plurality of the through holes are formed. Forming recesses on both sides of the semiconductor substrate;
Processing the inside of the recess of the surface of the semiconductor substrate, forming a through hole in a beam and a part of the beam;
Processing the inside of the recess on the back surface of the semiconductor substrate, forming a weight supported by the beam and a through hole in a part of the weight;
A step of laminating and forming the fixed electrode 1 on the surface of the flat upper glass substrate;
Bonding the upper glass substrate to the surface of the semiconductor substrate such that the fixed electrode 2 is laminated on the surface of the flat lower glass substrate, and the fixed electrode 1 is disposed at a position opposite to the weight; Bonding the lower glass substrate to the back surface of the semiconductor substrate so that the fixed electrode 2 is disposed at a position opposite to the weight;
A method for manufacturing a capacitive dynamic quantity sensor, comprising: A semiconductor substrate having a weight supported by a beam and displaced by a mechanical quantity such as acceleration or angular velocity applied from the outside;
An upper glass substrate that is bonded to a part of the surface of the semiconductor substrate and in which a fixed electrode 1 is disposed at a position opposed to the weight with a minute gap 1 therebetween;
A lower glass substrate formed by laminating a fixed electrode 2 bonded to a part of the back surface of the semiconductor substrate and arranged with a minute gap 2 at a position opposed to the weight;
A capacitive mechanical quantity sensor that measures the mechanical quantity from a change in capacitance between the movable electrode made of the weight and the fixed electrode 1 and a change in capacitance between the movable electrode made of the weight and the fixed electrode 2 due to the displacement of the weight. In
In manufacturing a capacitive mechanical quantity sensor, wherein a through hole is formed in a part of the beam,
The method of manufacturing a capacitive dynamic quantity sensor, wherein the beam and a through hole formed in a part of the beam are formed by the same etching process. A semiconductor substrate having a weight which is supported by a beam and which is displaced by a mechanical quantity composed of acceleration or angular velocity applied from the outside;
An upper glass substrate that is bonded to a part of the surface of the semiconductor substrate and in which a fixed electrode 1 is disposed at a position opposed to the weight with a minute gap 1 therebetween;
A lower glass substrate formed by laminating a fixed electrode 2 bonded to a part of the back surface of the semiconductor substrate and arranged with a minute gap 2 at a position opposed to the weight;
A capacitive mechanical quantity sensor that measures the mechanical quantity from a change in capacitance between the movable electrode made of the weight and the fixed electrode 1 and a change in capacitance between the movable electrode made of the weight and the fixed electrode 2 due to the displacement of the weight. In
In manufacturing a capacitive dynamic quantity sensor, wherein a through hole is formed in a part of the weight,
The method of manufacturing a capacitive dynamic quantity sensor, wherein the weight and a through hole formed in a part of the weight are formed by the same etching process.

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