JP2003101033A - Semiconductor acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in a conventional three-axis semiconductor acceleration sensor having, respectively four piezo-resistance devices on the respective axes of a flexible part, that since the resistance values of respective parts of lead-out electrodes are not taken into account in pattern design, the zero-point output voltage of the Z-axis, in particular, is as high as several mV. SOLUTION: The design of the electrode pattern of a lead-out electrode, connected to a piezo-resistance device provided on a center weight side, and an electrode pattern of the lead-out electrode, with which the piezo-resistance device provided on a fixed part side is connected to an external connection terminal, is worked out fully, to make the resistance values of both lead-out electrodes approximately equal to the resistance value of the electrode pattern on a beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a triaxial semiconductor type acceleration sensor for detecting a resistance change of a piezoresistive element formed in a flexible portion.

[0002]

2. Description of the Related Art As a conventional triaxial semiconductor type acceleration sensor, for example, there is one described in Japanese Patent Laid-Open No. 63-266359, and two pairs of beams which are made of a thin portion of a Si single crystal substrate and are orthogonal to each other. The flexible structure has a flexible portion, and the central weight body made of the thick portion of the Si single crystal substrate and the peripheral fixed portion are connected by the flexible portion, and the X-axis direction and the Z-axis direction are the same. on the beam, also to detect other piezoresistive element formed on the beam orthogonal to the Y-axis direction to this, the basic structure formed by piezoresistive elements for each axis 4 _Ke is formed on the beams It is shown. Although the conventional example does not describe the arrangement of the extraction electrode or the electrode connection terminal to the outside, the pattern width of the conventional extraction electrode is constant and the wiring resistance thereof is not taken into consideration. FIG. 7 is an enlarged view of the X- and Z-axis dotted line frame portions of FIG. 7 in which the extraction electrodes and external connection terminals are arranged in the conventional 3-axis acceleration sensor structure based on the conventional concept. , And ZZ in FIG.
A partial sectional view in the axial direction is shown. It will be explained below that the resistance value of the extraction electrode and the arrangement of the external connection terminals are also important points in realizing a compact and high-performance triaxial acceleration sensor.

First, the overall structure will be described. This is a central weight body 2 composed of a thick portion of a Si single crystal substrate, a fixed portion 1 arranged so as to surround the central weight body 2, and a thin portion of the Si single crystal substrate connecting the weight body 2 and the fixed portion 1. Two pairs of beam-shaped flexible portions 3a, 3b, 3c, which are orthogonal to each other,
3d and each axis 4 provided so as to correspond to two directions (X and Y) on the flexible portion and a direction (Z) perpendicular to the flexible portion.
_And piezoresistive elements 11 to 34.

From FIGS. 8 and 9, a protective film 41 made of a thin film of SiO ₂ or SiN is formed on the piezoresistive element.
Is formed, and lead-out electrodes 40 made of a metal thin film such as aluminum connected to both ends of the piezoresistive element via through holes 40a are formed thereon. The lead-out electrode group is provided on the peripheral fixed portion 1. The external electrode terminals 42 are connected to each other.

This conventional example detects triaxial acceleration. The principle of detection is that the deflection of the flexible portion when the center weight body 2 is displaced by receiving the force due to the acceleration is applied to the flexible portion. By detecting the change in the resistance value of the formed piezoresistive elements 11 to 34, the acceleration in the three axis directions is detected. The principle will be described in detail with reference to the drawings.

The principle of acceleration detection will be described with reference to FIGS. Since the X direction and the Y direction are the same, the X direction and the Z direction are representatively shown in these drawings. Figure 10
(A) is a cross-sectional view schematically showing how the flexible portions 3a, 3c are deformed by acceleration in the X direction, and shows a piezoresistive element Rx.
A tensile stress is applied to Rx1 and Rx3, and a compressive stress is applied to Rx2 and Rx4. At this time, piezoresistive elements Rx1 and Rx are applied.
The resistance values of 3 and Rx2 and Rx4 increase and decrease, respectively. Further, FIG. 11 shows how to assemble the bridge of each axis and the detection circuit. In FIG. 10 (a), when the force of Fx is applied to the weight body by the acceleration in the X direction, the piezo resistance R
x1 and Rx3 increase in value, and Rx2 and Rx
4 decreases, but due to this change, the detection circuit shown in FIG. 11A outputs a voltage in the X direction, but the voltage in the Z direction is different because the connection of the resistance of the bridge is different from that of the X direction. The increase or decrease in the resistance value of is canceled out and the voltage is zero. On the contrary, as shown in FIG. 10B, when the force of Fz is applied by the acceleration in the Z direction, the piezo resistances Rz1 and Rz are
4 increases its value and decreases Rz2 and Rz3. Due to this change, the detection circuit shown in FIG. 11B outputs a voltage in the Z direction, but the voltage in the X direction is
Since the connection of the resistance of the bridge is different from that of the Z direction, the increase and decrease of each resistance value is offset and the voltage is zero. In this way, triaxial acceleration can be detected.

[0007]

As described above, the piezoresistive acceleration sensor detects the unbalanced voltage of the bridge circuit. However, in the actual bridge circuit, other than the piezoresistor, the explanation will be given with reference to FIG. Extracted electrode pattern 4
Zero resistance comes in. Piezoresistive elements of each shaft 4 _Ke is designed in the same way, generally the extraction electrode pattern 40 is also point symmetric or line-symmetric to each beam of a pair of each axis pattern shape when it is designed in the same pattern, the Since the resistance value of the same pattern shape part of each part of the extraction electrode is also substantially equal, in the following description, the pattern part of each part of each extraction electrode is given the same symbol, and its resistance value is also described by the same symbol. To

First, in FIG. 7, the lead-out electrode patterns 40 of the piezoresistive elements 11, 12 and 13, 14 on the two beams of the X axis are divided into four parts, 40ax, 40ax.
The same reference numerals as bx, 40cx, 440dx are attached, and the resistance values corresponding to the respective are also Rax, Rbx, Rcx, Rd.
It is represented by the same symbol as x. Similarly, the Y-axis lead electrode pattern 40 is set to 40ay, 40by, 40cy, 40dy.
And divide the resistance value of each part into Ray, Rby, Rc
The y-axis, Rdy-axis, and Z-axis extraction electrode patterns 40 are divided into 40az, 40bz, 40cz, and 40dz, and the resistance values of the respective portions are set as Raz, Rbz, Rcz, and Rdz. Here, 40bx, 40by, and 40bz are each axis 2
Lead-out electrode patterns 4 for the X-axis, Y-axis, and Z-axis, which are located in the center of one beam and connect two piezoresistive elements (for example, X-axis is 11 and 12 and 13 and 14), respectively.
A part of 0, 40ax, 40ay, 40az, is an extraction electrode pattern part 40bx, 40by, 40bz at the center of the beam of each axis from the external electrode terminal 42 arranged on the fixed part 1.
A part of the X-axis, Y-axis, and Z-axis lead-out electrode patterns 40, 40cx, 40c until they are connected to
y and 40 cz are external electrode terminals 4 arranged on the fixed portion 1.
X-axis, Y-axis, and Z-axis lead-out electrodes that connect from 2 to the connection part on the fixed part side of each axis piezoresistive element (for example, X-axis is piezoresistive elements 11 and 14) located on the fixed part 1 side. Part of the pattern 40, 40dx is X
From the connecting portion of the two piezoresistive elements 12 and 13 of the X axis located on the side of the central weight body portion 2 of the axis, pass through the central weight body 2 and the beam 3b and the central weight body 2 and the beam 3d, respectively. A part of the extraction electrode pattern 40 connected to the external connection terminal 42 arranged on the fixed part 1 and 40 dy are two Y-axis piezoresistive elements 22 located on the side of the central weight body part 2;
A part of the extraction electrode pattern 40 that extends from the connection portion 23 to the external connection terminal 42 disposed on the fixed portion 1 through the central weight body 2 and the beams 3d and 3b, respectively.
0dz is arranged on the fixed portion 1 from the connecting portion of the two Z-axis piezoresistive elements 32 and 33 located on the side of the central weight body portion 2 through the central weight body 2 and the beams 3d and 3b. It refers to a part of the extraction electrode pattern 40 that is connected to the external connection terminal 42. Hereinafter, since the X axis and the Y axis are the same, the X axis and the Z axis will be representatively described. When the bridge circuit is rewritten in consideration of the wiring resistance value of each of the four divided parts of the extraction electrode pattern 40, it becomes as shown in FIG. In the figure, (a) shows an X-axis detection circuit, and (b) shows a Z-axis detection circuit.

[0009] First, looking at the X-axis, the resistance value Rax lead electrode pattern, Rbx, RCX, even subjected to any Rdx, 4 for piezoresistive _Ke is designed to the same value as the initial value, the bridge It can be seen from the connection method that the overall resistance balance is maintained and the zero point output is not affected. The same applies to the Y axis. Next, looking at the Z-axis, the way of connecting the Z-axis is different from that of the X-axis and the Y-axis as described above with reference to FIG.
As is clear from (b), Rcz and Rdz are exchanged and enter the bridge circuit.

Therefore, it can be seen that the zero point output is affected depending on the values of Rcz and Rdz. From the above definition, Rcz is the piezoresistive element 31, 34 on the fixed portion 1 side.
To the external connection terminal 42 to the extraction electrode pattern 40
The resistance value of cz, or Rdz, is the extraction electrode pattern 40dz of the piezoresistive elements 32 and 33 on the side of the central weight body 2.
Is the resistance value of. That is, the length of 40 cz is much shorter than that of 40 dz, and therefore the resistance value is also small. For example, when an aluminum thin film of about 0.3 μm is used for the extraction electrode pattern, Rcz is slightly less than 1 Ω and Rdz is about 5 Ω, and the difference is quite large. At this time, the zero output is set to any piezo resistance value. Depending on how you do it, it will be several mV. The specification of the zero-point output has come to be required to have a value of 5 mV or less, and the influence of the resistance value of the extraction electrode on the zero-point output cannot be ignored. Further, as the needs of the acceleration sensor, further smaller size and higher sensitivity are required, and in order to meet this, it is necessary to make the beam width as narrow and long as possible. There is no choice but to make the pattern as fine as possible. In other words, downsizing,
To meet the demand for higher sensitivity, the resistance value of the extraction electrode tends to increase and the zero-point output tends to increase.

Therefore, the Z-axis zero-point output due to the imbalance of the resistance value of the extraction electrode, which has not been a problem because the chip size is large and the pattern width of the extraction electrode is wide, has been demanded by miniaturization and high sensitivity. It has become a big issue. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a small-sized and highly sensitive semiconductor triaxial acceleration sensor having a small zero-point output voltage.

[0012]

According to a first aspect of the present invention, at least the Z-axis lead-out electrode is connected to a piezoresistive element disposed on the weight body side, and after it is once drawn out to the weight body section. In the extraction electrode pattern that is connected to the external connection terminals of the peripheral fixed part through the beam, the part except the extraction electrode pattern part on the beam, that is, the extraction electrode pattern part and the fixed part in the weight body part, By making the pattern width of a certain extraction electrode pattern portion wider than the extraction electrode pattern portion on the beam by 2 times or more, preferably 4 times or more, the resistance value of the entire extraction electrode is substantially determined by the extraction electrode pattern portion on the beam. The resistance value of the extraction electrode that connects the piezoresistive element arranged on the fixed part side to the external connection terminal as described above. It is that in which substantially equal to the resistance value of the pattern portion on the beam extraction electrode which is connected to the child. As described above, in the present invention, the method of adjusting the resistance value is performed by using the pattern shape. However, a method of changing the thickness of the extraction electrode may be considered. In that case, the thickness of the extraction electrode of each part is changed. It is necessary to repeat the process of forming the electrode thin film and the photoetching process a plurality of times, which complicates the manufacturing process, which is not preferable.

The second invention of the present application is the same as the first invention of the present application, with regard to the shape of the extraction electrode for connecting the piezoresistive element arranged on the fixed portion side to the external connection terminal, the width of which is on the weight body side. The lead electrode connected to the piezoresistive element has a shape narrower than the pattern width on the beam, and has a shape in which it is folded several times as necessary, and the resistance value of the electrode pattern portion is the piezoresistive element on the weight body side. That is, the resistance value of the pattern portion on the beam of the extraction electrode connected to is approximately equal to the resistance value.

A third invention of the present application is the X-axis (or Y) arranged on a pair of beams in the first and second inventions of the present application.
It is connected to a total of 4 _Ke piezoresistive element axis) to be located to the weight body portion side of the Z-axis, the four lead-out electrode patterns drawn to the weight body on the, Y-axis (or X-axis) The X-axis (or Y-axis) can be pulled out separately in two directions.
And the Z axis is arranged at an equal position in the beam width direction.

[0015]

According to the first aspect of the invention, after being connected to the piezoresistive element arranged on the weight body side and once being pulled out to the weight body section, it is passed through the beam and externally connected to the peripheral fixed portion. The lead-out electrode pattern shape connected to the terminal and the lead-out electrode pattern shape that connects the piezoresistive element arranged on the fixed side to the external connection terminal are based on the beam shape that must be designed with the most consideration for detection sensitivity. As a result, the pattern shapes of both can be determined, and there is an effect that a low-zero output can be easily achieved with high sensitivity. In other words, in order to make the resistance values of the two with greatly different lengths substantially equal, the detection sensitivity, which is the most important characteristic parameter as an acceleration sensor, is not sacrificed, and zero-point output can be easily performed without increasing the chip size. There is an effect that can be reduced.

According to the second invention, the width of the lead-out electrode pattern for connecting the piezoresistive element arranged on the fixed portion side to the external connection terminal is made narrower than the width of the electrode pattern on the beam.
By adopting a shape with multiple turns as necessary, it is possible to easily balance the resistance of the extraction electrode pattern even if the beam length is increased, and while maintaining the chip size compared to the first invention. There is an effect that the zero-point output can be further reduced, or the zero-point output can be reduced with high sensitivity even with a smaller size. Further, the degree of freedom in layout of the external connection terminals can be increased, and it is possible to combine the external connection terminals on two sides of the chip while keeping the zero-point output small.

According to the third invention, even if the two detection axes of the X-axis (or Y-axis) and the Z-axis are arranged on the pair of beams, the beam width can be narrowed, so that the zero-point output is reduced. Moreover, there is an effect that the size is small and the sensitivity is easily increased.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to Examples.

An embodiment according to the first invention is shown in FIG. The present embodiment is an example in which the present invention is applied to the triaxial basic structure of the conventional example described in FIG. This is different from the conventional triaxial semiconductor acceleration sensor in the arrangement of the external connection terminal of the lead electrode on the Z-axis central weight body side. In FIG. 1, the same parts as those in FIG. 6 are denoted by the same reference numerals for the sake of clarity.
As described above, the basic structure is a beam-like structure including a central weight body 2 and a fixing portion 1 arranged so as to surround the central weight body 2, and a thin portion of a Si single crystal substrate connecting the weight body 2 and the fixing portion 1. flexible portion 3a of, 3b, 3c, 2 two directions on 3d and the movable flexure (X and Y) and movable flexure axes 4 _Quai provided so as to correspond to the direction (Z) perpendicular to the Piezoresistive element group 11
To 34. The X- and Y-axis lead-out electrodes 40 from the piezoresistive element group to the external connection terminals have a point-symmetrical shape with the weight body portion 2 as the center and have a constant pattern width, and the present invention is applied to the Z-axis lead-out electrodes. The pattern was designed by applying the resistance value of each part. That is, X axis and Y
Regarding the axis, as in the conventional example, the electrode patterns of the respective portions in the two beam directions have the same shape, and therefore their resistance values also do not affect the zero-point output voltage.

The Z axis will be described in detail. The lead electrode pattern connecting the Z-axis piezoresistive element 11 and the external connection terminal 42 is 40 cz, and the lead electrode pattern connecting the piezoresistive elements 11 and 12 and 13 and 14 is 4.
0bz, the external connection terminal 42 and the electrode pattern 4 at the center of the beam
The electrode pattern connecting 0bz is 40az, the extraction electrode pattern connected to the weight side connection portion of the piezoresistive elements 12 and 13 is 40dz, and the extraction electrode 40dz is
It was pulled out to the external connection terminal 42 on the fixed portion 1 through the beams 3c and 3b having the Z-axis detection axis. As described with reference to FIG. 12, if the resistance values of the electrode patterns 40cz and 40dz are not equal, the zero-point output is affected. In the present embodiment, the electrode patterns 40cz and 40dz can be made to have substantially the same resistance value by having a pattern shape as described in the manufacturing method described later, and the zero-point output can be suppressed to a level where there is no practical problem. It was

Next, the manufacturing method of this embodiment will be described. FIG. 2 shows a part of the cross section in the XX direction for explaining the main steps. In the description of this manufacturing process, the thickness S of the flexible portion 3 is controlled so that it can be controlled with high precision.
An example using an OI wafer will be described. What is SOI Sil
It is an icon on insulator,
N type Si was used. As shown in FIG. 2, the SOI wafer is composed of a Si base substrate 60, a surface SOI layer 80 which is an Si active layer, and a SiO ₂ layer 70 which is between them and is used as an etching stopper. It is a manufactured Si semiconductor substrate. The thickness of each is, for example, 500 to 625 μm for the base substrate, 1 μm for SiO _2, and 10 μm for the SOI layer for a high-sensitivity acceleration sensor.

At the beginning of the manufacturing process, first, the SOI layer 8
A pattern of a predetermined shape is formed on the surface of 0 using a photoresist or a thermally oxidized SiO ₂ film as a mask, and boron-diffused piezoresistors 11 and 12 are formed by an impurity diffusion process such as ion implantation (FIG. 2A). ). As the surface impurity concentration, about 2 × 10 ¹⁸ was selected from the viewpoint of both temperature characteristics and sensitivity.

Next, a protective film 41 is formed for the purpose of protecting the piezoresistors 11 and 12 (FIG. 2B). As the protective film 41, SiO ₂ and PSG (Phosphorus Silicated) which are generally used in semiconductors are used.
A glass multilayer film is used to provide a gettering effect for mobile ions. Instead of the two-layer film of SiO ₂ and PSG, a two-layer film of SiO ₂ and SiN may be used. The thickness of the protective film 41 is preferably as thin as possible to reduce the stress in order to improve the sensitivity, and is set to 0.3 to 0.5 μm.

Next, through holes 40a for connecting electrodes are formed in the protective films 41 on both ends of the piezoresistors 11 and 12 by wet etching mainly using hydrofluoric acid (FIG. 2).
(C)).

Next, in order to form the electrode wiring, first, an aluminum alloy (a main composition of which is aluminum, copper, Si, etc.) is formed by sputtering. Thickness is 0.3-0.5 μm
However, it is preferable that the stress is as small as possible, and the thickness is preferably thin. The extraction electrode 40 was formed by photoetching (FIG. 2D). At this time, the X and Y axis lead-out electrodes had the same pattern width in each part as in the conventional example, and the shape was point-symmetrical about the weight body part 2. Thereby, the electrodes 40ax, 40bx, 40cx, 40dx and 40a of the respective portions of the extraction electrode are formed.
y, 40by, 40cy, and 40dy can be made substantially the same in the two beam directions, and there is no influence on the zero point output. On the other hand, with respect to the Z-axis lead electrode, the lead electrode 40dz from the piezoresistive elements 32 and 33 disposed on the weight body 2 side has the width of the electrode pattern portion on the weight body portion and the fixed portion on the beam. The width of the electrode pattern portion was about 5 times, and the width of the electrode pattern on the beam was the same as the X and Y axes. In addition, the extraction electrodes 4 of the piezoresistive elements 31 and 34 arranged on the fixed portion side.
The width and length of 0 cz were made substantially the same as the electrode pattern portion on the beam of the extraction electrode 40dz.

Next, although not shown in FIG.
The SOI layer 800 shown in (a) is etched by a dry etching method or the like to form a penetrating pattern 5 to the SOI layer 800 shown in FIG.

Next, the base substrate 60 on the back surface is aligned with the piezoresistive elements 11 and 12 on the front surface and the penetrating pattern 5 to the SOI layer 800 by using a double-side aligner device, and the weight body 2 and the fixing portion are aligned. 1. Form a photoresist mask in the shape of 1 and dry-etch the Si base substrate 6
Etching 0, and SiO as an etching stopper
_{The two} layers 70 were removed by wet etching (FIG. 2 (e)).
In this step, the flexible portions 3a, 3b, 3c, 3d are formed. However, it may be better to leave the SiO ₂ layer 70 of the etching stopper without removing it in order to balance the entire stress. The method of leaving a part of the SiO ₂ layer 70 is also applicable. After that, a large number of acceleration sensor elements formed on the wafer were cut into chips using a dicer or the like, and an acceleration sensor was completed through a process of assembling a package or the like.

As described above, in this embodiment, the electrode pattern 4
For 0 dz, the width of the pattern portion on the weight body portion and the fixed portion is set to about 5 times the pattern width on the beam, and for the electrode pattern 40 cz, the width and length of the electrode pattern 40 dz are set to the beam of the electrode pattern 40 dz. By making the width and length of the upper pattern portion approximately the same, the resistance values of both can be made substantially the same, and the zero-point output voltage due to the unbalanced portion of the resistance can be obtained to be a sufficiently small value of 0.5 mV or less. It was
In order to reduce the resistance value of the electrode pattern 40dz, a method of changing the thickness of the aluminum thin film may be considered, but in that case, the steps of forming the aluminum thin film and photoetching are repeated a plurality of times, and the manufacturing process is It becomes long and is not desirable.

Next, embodiments according to the second and third inventions are shown in FIGS. 3, 4 and 5. In this embodiment, the second invention is applied to the same basic structure as that of the embodiment of the first invention shown in FIG. 1. FIG. 3 is a front view showing an embodiment of the second and third inventions. 4 is an enlarged view of the vicinity of the external connection terminals of the X and Z axes of FIG. 3 for explaining the second invention, and FIG. 5 is an enlarged view of one beam portion of the X and Z axes of FIG. 2 is a diagram for explaining the second invention, and the same portions as those in FIG. 1 are denoted by the same reference numerals.

First, the second invention will be described with reference to FIGS. 3, 4 and 5. Similarly to the description of the first aspect of the invention, the Z-axis is a problem for zero-point output, so in the following description, Z
I will focus on the axis. Piezoresistive elements 32, 3 on the weight side
The extraction electrode 40dz from 3 passed through the beams 3d and 3b of the Y axis and was connected to the external connection terminal 42 on the fixed portion 1. Regarding the shape of the lead electrode 40dz, the weight body portion 1
The electrode pattern portion on the fixed portion 2 is wider than the electrode pattern portion on the Y-axis beam by a minimum of about three times, and the resistance value of the extraction electrode 40dz is almost the same as the resistance value of the pattern portion on the beam. I decided. Further, the width of the extraction electrode 40cz of the piezoresistive elements 31 and 34 on the fixed portion side is set to about 70% of the width of the electrode pattern portion on the beam, and 3
By providing a shape with a number of turns, the resistance value can be made substantially equal to the resistance value of the pattern portion on the beam of the extraction electrode 40dz, and the external connection terminal is closest to the piezoresistive elements 31 and 34. I was able to place it. That is, even in the layout of the external connection terminal 42 in which the difference between the resistance values of the extraction electrodes 40dz and 40cz is the largest, the resistance values of the both can be substantially equalized, and therefore, the zero point output due to the imbalance of the resistance values is 0.5 mV
It was so small that it was almost negligible. Further, as a modification of the present invention, the extraction electrode 40cz on the fixed portion side is formed into the above-described shape, and the width beyond that is sufficiently wide such that the width is 10 times or more the width of the electrode pattern portion on the beam. With this, there is an effect that the external connection terminals can be arranged at arbitrary positions. For example, in FIG.
In arranging the external connection terminals in total 18 _Ke the four sides of the chip, but it is also possible to put together the two sides without deteriorating the zero point output voltage. An example thereof is shown in FIG. Since the pattern shape of the extraction electrode has been sufficiently described above, it is omitted in FIG. In the present example, allocates eight _Ke of the Y-axis in the X and Z-axis direction, and arranged left and right 9 _Ke increments external connection terminal 42.

Next, the third invention will be described with reference to FIG. In the present embodiment, the two lead electrodes 40 from the piezoresistive elements 12 and 32 located on the weight body side on the X-axis and Z-axis beams 3c pass on the Y-axis beam 3d and the fixed portion side. Further, two lead electrodes 40 from the piezoresistive elements 13 and 33 on the X-axis and Z-axis beams 3d pass through on the Y-axis beams 3b to the external connection terminals 42 on the fixed portion side. but, the number of external connection terminals, respectively to the X and Z-axis directions 4 _Ke, respectively 5 _Ke in the Y-axis direction is arranged. Further, the X and Z axes are arranged at equal positions in the width direction of the beams 3a and 3c so that the beam width can be easily narrowed. In the conventional X-axis and the Y-axis, since the twist of one beam affects the characteristics, both of them are arranged at the center of the beam width direction as shown in the conventional example of FIG. However, even if the X-axis is arranged closer to the end than the center of the beam width and the Y-axis is arranged closer to the center of the beam width as in the present embodiment, the beam width is narrowed to about 200 μm or less to improve the sensitivity. In such a case, there was no great difference in the characteristics such as the detection sensitivity of the X and Y axes and the sensitivity of the other axes, and conversely, it was found that the beam width was easily designed and the sensitivity was advantageous. Note that the lead-out electrodes 40dx and 40dz on the X- and Z-axis weight bodies are led out in the same beam 3b, 3d direction. However, as in the conventional example shown in FIG. 7, the X-axis and the Z-axis are separated. It may be divided into

Further, according to this embodiment, there are the following attendant effects. The X- and Y-axis extraction electrodes 40 were also designed so that their resistance values were substantially determined by the electrode pattern portion on the beam, similarly to the Z-axis extraction electrode 40. As a result, the voltage drop in each part of the extraction electrode connected to the piezoresistive element in the same arrangement on each axis is almost equal, that is, the effective drive voltage applied to the piezoresistive element is applied to all piezoresistive elements. It was almost equal.
Further, the X, Y, and Z axis lead-out electrodes increase the pattern area in the vicinity of the beams of the weight body portion 2 and the fixed portion 1 and have an effect of improving the heat radiation effect. Therefore, in the present embodiment, there was an effect that the stability such as the energization fluctuation can be improved as compared with the conventional case due to these accompanying effects.

[0033]

As described above, according to the present invention, a triaxial semiconductor type acceleration sensor which is small in size, highly sensitive, and has a small zero-point output voltage can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a front view showing a first embodiment according to the present invention.

FIG. 2 is a process sectional view showing a method of manufacturing an acceleration sensor according to the present invention.

FIG. 3 is a front view showing second and third embodiments of the present invention.

FIG. 4 is an enlarged view of the vicinity of external connection terminals on the X and Z axes of FIG.

5 is an enlarged view of a part of the X- and Z-axis beams and FIG.

FIG. 6 is a front view showing an arrangement of external connection terminals which is another embodiment of the second invention.

FIG. 7 is a front view showing the structure of a conventional semiconductor acceleration sensor.

8 is an enlarged front view of one of the X-axis and Z-axis beam portions of FIG.

9 is a sectional view taken along the Z-axis of FIG.

FIG. 10 is a cross-sectional view showing a state of a conventional semiconductor acceleration sensor when acceleration is applied in the X and Z axis directions.

FIG. 11 is a bridge circuit diagram of a conventional acceleration sensor.

FIG. 12 is an actual bridge circuit diagram in which the resistance of the extraction electrode of the triaxial acceleration sensor is taken into consideration.

[Explanation of reference numerals] 1 fixing part, 2 weight body, 3 flexible part, 40 extraction electrode, 41 protective film, 42 electrode terminal, 11 12 13
14 21 22 23 24 24 3132 33 3
4 piezoresistive elements, 3a to 3d flexible parts, 5 SOI
Penetration pattern etched into layer 800

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4M112 AA02 BA01 CA23 CA26 CA27                       CA33 DA03 DA04 DA10 DA12                       EA02 EA06 EA10 EA11 EA13                       FA01 FA03

Claims (3)

[Claims] 1. A central weight body portion formed of a thick portion of a Si single crystal substrate, a fixing portion arranged so as to surround the weight body portion, and Si connecting the weight body portion and the fixing portion. A diaphragm-shaped or a plurality of pairs of beam-shaped flexible portions formed of a thin portion of a single crystal substrate, two orthogonal detection axes (X and Y axes) on the flexible portions, and one perpendicular to the flexible portions. One of in response to the detection axis (Z axis), consists of a piezo-resistive element group of each of axes installed on the movable flexure 4 _Ke, piezoresistors of the respective shaft 4 _Ke constitute a bridge detection circuit A semiconductor acceleration sensor that is connected by thin-film extraction electrodes like
At least for the lead-out electrode of the piezoresistive element in the Z-axis direction, a) The width of the pattern portion on the weight body portion and the fixed portion of the lead-out electrode connected to the piezoresistive element arranged on the weight body portion side is on the beam. Of the lead-out electrode pattern portion, and b) the resistance value of the lead-out electrode that connects the piezoresistive element arranged on the fixed portion side to the external connection terminal with the weight body portion side. The semiconductor acceleration sensor, wherein the resistance value of the pattern portion on the beam of the extraction electrode connected to the piezoresistive element is substantially equal to the resistance value. 2. The semiconductor acceleration sensor according to claim 1, wherein the lead electrode for connecting the piezoresistive element arranged on the fixed portion side to the external connection terminal has a pattern width arranged on the weight body portion side. The width of the pattern of the lead-out electrode connected to the piezoresistive element is smaller than the pattern width on the beam, and the electrode pattern part has a folded shape a plurality of times when necessary, and the resistance value of the electrode pattern part is arranged on the weight body part side. A semiconductor acceleration sensor having a resistance value substantially equal to a resistance value of a pattern portion on a beam of an extraction electrode connected to a piezoresistive element. 3. The semiconductor acceleration sensor according to claim 1, wherein the X-axis (or Y-axis) and the Z-axis arranged on the pair of beams are located on the weight body side. _Set the extraction electrodes of the four piezoresistive elements to the Y-axis (or X-axis) 2
It is divided into two in each direction and pulled out, and the X-axis (or Y
Axis) and the Z axis are arranged at even positions in the width direction of the beam.