JP2003222560A - Force detecting element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To actualize a force detecting element 1 with high detection accuracy by inhibiting current flowing through strain gauge parts 126 from leaking to the exterior. <P>SOLUTION: This force detecting element 1 is equipped with a force detection block 120 and a force transmission block 138. The block 120 has a semiconductor substrate 122, first insulation layers 124, and the strain gauge parts 126. The first insulation layers 124b and 124d partly cover a top surface of the substrate 122. The gauge parts 126b and 126d are formed in projection parts 130b and 130d extending along top surfaces of the insulation layers 124b and 124d. The gauge parts 126b and 126d are formed out of semiconductor material (first semiconductor layer) whose resistance value changes depending on stress acting thereon. The widths L4 of the insulation layers 124b and 124d are larger than the widths L1 of the gauge parts 126b and 126d. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a force sensing element and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 11 shows a perspective view of a conventional force detecting element 1, and FIG. 12 shows a sectional view taken along line XII-XII of FIG.
As shown in FIG. 11, the force detection element 1 includes a support base 21,
The force detection block 20 and the force transmission block 38 are provided. The force detection block 20 is formed with four square-shaped protruding portions 30a to 30d protruding from the main surface 20s. Although the subscripts b and d are shown in FIG. 12, the contents described below are common to the subscripts a and c.
The description will be made without subscripts. As shown in FIG. 12, the force detection block 20 includes a semiconductor substrate 22 and a first insulating layer 24.
And has a laminated structure of the first semiconductor layer 26. Protrusion 30
a to 30d are the second semiconductor layer 23 and the first insulating layer 24.
And a first semiconductor layer 26. The width of the first insulating layer 24 is equal to the width of the first semiconductor layer 26 located thereabove. The first semiconductor layer 26 functions as a strain gauge portion, and the resistance value changes according to the stress acting. The surface of the force detection block 20 is covered with the second insulating layer 28. Further, as shown in FIG. 11, the force detection block 20 is provided with electrodes 32 a to 32 d electrically connected to the first semiconductor layer (strain gauge portion) 26 in the protrusion 30. The force transmission block 38 is attached to the top surfaces of the protrusions 30a to 30d.

When the protrusion 30 is formed, the external force acting on the top surface of the force transmission block 38 is concentratedly transmitted to the protrusion 30. Therefore, when the strain gauge portion 26 is formed in the protruding portion 30, the stress acting on the strain gauge portion 26 can be increased. Therefore, the amount of change in the resistance value of the strain gauge section 26 can be increased, and high sensitivity can be realized.

13 to 1 showing an example of a method of manufacturing the force sensing element 1 having the above-described structure, showing a manufacturing process of a portion of the subscript b in FIG.
This will be described with reference to FIG. First, the force detection block 20 having a laminated structure of the silicon substrate 22, the silicon oxide layer 24, and the silicon layer 26 is formed. Then, a resist film 31b is formed (FIG. 13). Next, force detection block 2
A predetermined area of the surface of 0 is masked with the resist layer 31b and dry-etched to a predetermined depth (FIG. 14). As a result, in the predetermined range, the first semiconductor layer 26b protruding from the main surface 20s of the force detection block 20 (silicon substrate 22), the first insulating layer 24b, and the second semiconductor layer 23b remain. These form the protrusion 30b. Next, the surfaces of the silicon substrate 22 and the protrusions 30b are oxidized by, for example, a thermal oxidation method. As a result, the second insulating layer 28b made of the silicon oxide layer is formed (FIG. 15). Next, the force transmission block 38 is attached to the top surface of the protrusion 30b (see FIG. 1).
6).

In the force sensing element 1 described above, the first insulating layer 24 is provided between the first semiconductor layer 26 and the second semiconductor layer 23. Further, the periphery of the first semiconductor layer 26 and the second semiconductor layer 23 is covered with the second insulating layer 28. As a result, the current flowing through the first semiconductor layer (strain gauge portion) 26 is prevented from leaking to the outside (typically, the second semiconductor layer 23 (semiconductor substrate 22)). When a current leaks from the first semiconductor layer 26 to the outside, the output electrodes 32b and 32d
The voltage value appearing at will change. As a result, the amount of change in the resistance value of the first semiconductor layer (strain gauge portion) 26 cannot be accurately obtained. As a result, it becomes impossible to accurately obtain the magnitude of the applied external force W.

[0006]

However, in the force sensing element 1 described above, although the first semiconductor layer 26 and the second semiconductor layer 23 are covered with the first insulating layer 26 and the second insulating layer 28, Actually, there is a problem that the current flowing through the first semiconductor layer (strain gauge portion) 26 leaks from the side surface of the first semiconductor layer 26 to the outside (in particular, the second semiconductor layer 23 (semiconductor substrate 22)). there were.

The reason for this is that a second layer is formed of a silicon oxide layer formed by oxidizing silicon by, for example, a thermal oxidation method.
The insulating layer 28 is formed on the surfaces of the first semiconductor layer 26 and the second semiconductor layer 23 made of silicon, but is almost formed on the surface (side surface in FIG. 12) of the first insulating layer 24 made of a silicon oxide layer. It is considered that it is not done. That is, FIG.
2, the second insulating layer 28 includes the first semiconductor layer 26.
b, 26d and the surface vicinity 2 of the second semiconductor layers 23b, 23d
8b-1 and 28d-1 are formed to have a substantially constant thickness, and the vicinity of the side surfaces 28b-2 of the first insulating layers 24b and 24d,
It is hardly formed on 28d-2. As a result, the first
The current flowing through the semiconductor layers (strain gauge portions) 26b and 26d is the side surface neighborhoods 28b-2 of the first insulating layers 24b and 24d,
This is because it is easy to leak from 28d-2 to the outside (in particular, the second semiconductor layers 23b and 23d (semiconductor substrate 22)) as indicated by arrow A.

On the other hand, temporarily, a silicon oxide film forming the second insulating layer 28 is formed by CVD (Chemical Vapor Depositio).
When it is formed by the method n), the second insulating layer 28 can be formed with a predetermined film thickness near the side surface of the first insulating layer 24. However, the silicon oxide film formed by the CVD method is mechanically and electrically inferior in quality to the silicon oxide film formed by the thermal oxidation method. Therefore, according to the configuration of the force sensing element 1 shown in FIG. 12, even when the second insulating layer 28 is formed by the CVD method, the current flowing through the first semiconductor layer 26 is external (especially the second semiconductor layer 23 (semiconductor substrate 22)). )) Easily leaks.

An object of the present invention is to realize a force detecting element with high detection accuracy by suppressing leakage of current flowing through a strain gauge section to the outside.

[0010]

A force sensing element embodying the present invention includes a substrate, a first insulating layer, and
It has a strain gauge section. The first insulating layer covers at least a part of the top surface of the substrate. The strain gauge section is the first
The semiconductor material is formed in the protrusion extending along the top surface of the insulating layer, and has a semiconductor material whose resistance value changes according to the stress acting (claim 1). The width of the first insulating layer is wider than the width of the strain gauge portion. The width of the first insulating layer may be wider than the width of the strain gauge portion on at least one side.
It is more preferable that the width of the first insulating layer is wider on both sides than the width of the strain gauge portion. According to this aspect, it is possible to prevent the current flowing through the strain gauge unit from leaking to the outside (for example, the substrate). Therefore, a force detection element with high detection accuracy can be realized. In particular, if the width of the first insulating layer is wider than the width of the strain gauge portion, the first insulating layer can block the path through which the current flowing through the strain gauge portion leaks from the side surface of the strain gauge portion to the substrate. Therefore, leakage of current from the side surface of the strain gauge portion to the substrate can be effectively suppressed.

It is preferable that a force transmission block that contacts the top surface of the protrusion is further provided (claim 2). According to this aspect, the external force can be uniformly applied to the strain gauge portion in the protrusion via the force transmission block.

[0012] The substrate further comprises a base portion protruding from the main surface of the substrate, the base portion having a first insulating layer, the width of the base portion is wider than the width of the protrusion portion, and the protrusion portion is the first insulating layer of the base portion. It preferably extends along the top surface of the layer (claim 3). According to this aspect, even if a large external force acts on the force transmission block and bends, the flexed force transmission block can be prevented from coming into contact with the opposing portion (the substrate, the insulating layer, or the like). Therefore, the range in which the force can be accurately detected can be increased.

It is preferable that a second insulating layer covering the top surface and the side surface of the strain gauge portion is further provided (claim 4). The second insulating layer preferably covers the top surface of the substrate at a position other than the base portion (claim 5). The second insulating layer is preferably formed of a silicon thermal oxide film (claim 6). According to these aspects, it is possible to effectively prevent the current flowing through the strain gauge portion from leaking to the outside (force transmission block or the like). In particular, when the second insulating layer is formed of a silicon thermal oxide film, current leakage can be suppressed more effectively.

The substrate is formed of a silicon substrate of an SOI (Silicon On Insulator) substrate, and the first insulating layer is SO.
It is preferable that the strain gauge portion is formed of the silicon oxide layer of the I substrate and the strain gauge portion is formed of the silicon active layer of the SOI substrate. According to this aspect, it is possible to effectively prevent the current flowing through the strain gauge section from leaking to the outside.

It is preferable that a leg portion extending from a bottom surface of the force transmission block is further provided, and a top surface of the protrusion is in contact with a bottom surface of the leg portion. According to this aspect, even if a large external force acts on the force transmission block to bend it, it is possible to prevent the deflected force transmission block from contacting the facing portion (the substrate, the first insulating layer, or the like). Therefore,
The range in which the force can be accurately detected can be increased.

A configuration may further be provided in which the first electrode and the second electrode are further provided, the electrodes are electrically connected to the strain gauge portion, and the electrodes for connecting the external terminals are only the first electrode and the second electrode ( Claim 9). According to this aspect, the detection sensitivity of the applied external force can be increased. In addition, it is easy to realize a force detection element having a simple structure, and it is easy to simplify the manufacturing process.

The force transmission block may further include a support portion for the force transmission block that does not include the strain gauge portion (claim 10). According to this aspect, the force transmission block can be supported more stably.

A method of manufacturing a force sensing element embodying the present invention is a method of manufacturing a force sensing element using an SOI (Silicon On Insulator) substrate having a silicon substrate, a silicon oxide layer and a silicon active layer. This method includes a step of masking a predetermined region of the silicon active layer with a first resist layer, a step of etching the SOI substrate until the silicon oxide layer is exposed, an unetched silicon active layer and a silicon oxide layer adjacent thereto. The method comprises masking the layer with a second resist layer and etching the unmasked silicon oxide layer and the silicon substrate (claim 11).

In this manufacturing method, the silicon active layer and the silicon oxide layer adjacent thereto are masked with the second resist layer. Then, the unmasked silicon oxide layer and the silicon substrate are etched. Thus, the silicon oxide layer protruding from the main surface of the silicon substrate and a part of the silicon substrate can be continuously formed without changing the resist layer. Therefore, according to this manufacturing method, it is possible to prevent the current flowing in the silicon active layer (strain gauge portion) from leaking to the outside (for example, the silicon substrate) and the portion where the flexed force transmission block faces (the silicon substrate or the insulating substrate). A structure capable of avoiding contact with a layer) can be efficiently manufactured.

To oxidize the surface of the SOI substrate, the SOI
It is preferable to further include a step of heating the substrate and a step of bringing the force transmission block into contact with the SOI substrate (claim 12). According to this aspect, it is possible to more effectively suppress the current flowing through the strain gauge portion from leaking to the outside.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) FIG. 1 is a perspective view of a force sensing element 101 of the first embodiment, and FIG.
A II sectional view is shown. As shown in FIG. 1, the force sensing element 1
01 includes a support 121, a force detection block 120, and a force transmission block 138. Note that, in FIG. 1, the force transmission block 138 is shown by a dashed line for clarity of illustration. The support 121 is a rectangular parallelepiped in a plan view and has a width (length of one side of the square) of about 1.
The height is 4 mm and the height is about 0.5 mm. The force detection block 120 is fixed to the upper surface of the support 121. The force detection block 120 includes the semiconductor substrate 122 and the base unit 1.
34a to 134d, and electrode pedestals 136a to 136d
And the protrusions 130a to 130d and the electrodes 132a to 13d.
2d etc. are provided.

The semiconductor substrate 122 is formed of an n-type silicon single crystal substrate. The semiconductor substrate 122 is
It is a rectangular parallelepiped when seen in a plan view, and has a width of about 1.
The height is 4 mm and the height is about 0.5 mm. The semiconductor substrate 122 may be made of gallium arsenide or the like. The substrate denoted by reference numeral 122 does not have to be formed of a semiconductor material. The base portions 134a to 134d are the force detection block 1
It protrudes from 20 main surfaces. Base portions 134a to 13
4d is formed in an elongated shape. Base portion 134a-
134d is located on the lower side and wider than the protrusions 130a to 130d (see FIG. 2). As shown in FIG. 1, the four base portions 134a to 134d have the same length and are formed in a square shape. As shown in FIG. 2, the base portions 134b and 134d are respectively provided in the second semiconductor layer 1
23b and 123d and the second semiconductor layers 123b and 123d.
First insulating layer 124 made of a silicon oxide film covering the top surface of the
b, 124d, and a second insulating layer 128 made of a silicon oxide film that covers the side surfaces of the second semiconductor layers 123b, 123d. The second semiconductor layers 123b and 123d can be said to be a part of the semiconductor substrate 122. Although illustration is omitted, the same applies to the base portions 134a and 134c. Figure 1
As shown in FIG. 4, the electrode pedestals 136a to 136d are formed by bases 134a to 134d.
It is in a position extending from one corner.

As shown in FIG. 2, the protrusions 130b, 13
0d projects from the top surfaces of the first insulating layers 124b and 124d. The protrusions 130a to 130d are formed in a mesa step shape having a flat top surface and are formed in an elongated shape. The protruding portions 130a to 130d are the base portions 134a to 1
Compared to 34d, it is located on the upper side and has a narrow width. Four
The protrusions 130a to 130d of the book have the same length and are formed in a square shape. As shown in FIG.
b and 130d are p-type first semiconductor layers (strain gauge portions) 126b and 126d, and the first semiconductor layer 126, respectively.
The second insulating layer 128 covers the top and side surfaces of the b and 126d. Although not shown, the same applies to the protrusions 130a and 130c. The protrusion 130 does not have to be formed in a mesa shape with a flat top surface. For example, the top surface of the protrusion 130 may be curved.

As shown in FIG. 1, electrodes 132a-132 are provided.
d is formed on the electrode pedestals 136a to 136d, respectively. The electrodes 132a to 132d have the protrusion 130.
It is electrically connected to the first semiconductor layer (strain gauge portion) 126 therein. The electrodes 132a to 132d are composed of a pair of input electrodes 132a and 132c and a pair of output electrodes 132b and 132d formed in a diagonal direction.

The top surface of the first semiconductor layer (strain gauge portion) 126 is the (110) plane. First semiconductor layers 126a-12
6d is arranged so that the piezo resistance coefficient changes according to π ₁₃ ′. First semiconductor layers 126b and 126d
The longitudinal direction (formed inside the protrusions 130b and 130d in FIG. 1) extends in the <110> direction. On the other hand, the first semiconductor layers 126a and 126c (the protruding portion 1 in FIG.
(Formed within 30a and 130c), the longitudinal direction extends in the <100> direction. Four strain gauge parts 12
A Wheatstone bridge is configured by 6a to 126d.

When the piezo resistance coefficient is π ₁₃ ′, (11
It has the maximum sensitivity in the <110> direction of the 0) plane and <100
The sensitivity is zero in the> direction. Therefore, the longitudinal direction is <11
In the strain gauge portions 126b and 126d extending in the 0> direction,
When compressive stress acts from the (110) plane, the resistance value changes (increases) due to the piezoresistive effect according to the stress. That is, the strain gauge sections 126b and 126d function as gauge resistances. On the other hand, in the strain gauge portions 126a and 126c whose longitudinal direction extends in the <100> direction, (11
Even if a compressive stress is applied from the 0) plane, the resistance value hardly changes. That is, the strain gauge sections 126a and 126c function as reference resistors.

The first semiconductor layer (strain gauge portion) 126 was originally an n-type layer, but has p-type impurities added thereto.
The p-type impurity concentration is on the order of 1 × 10 ¹⁸ / cm ³ or 1 × 10 ²⁰ / cm ³ . The resistivity is 0.
It is 001 Ω · cm. Since the impurity concentration is sufficiently high, paragraphs 0058 to 0 of JP-A-8-271363 are disclosed.
The temperature compensation action described in 062 is obtained. Further, although the first semiconductor layer 126 has a high concentration, it has a high resistance value because it is thin and thin, and it is easy to measure changes in the resistance value.

The force transmission block 138 is placed on the top surfaces of the square-shaped projections 130a to 130d. In order to obtain good detection characteristics in various environments, it is preferable to attach or fix the force transmission block 138 to the force detection block 120 by anodic bonding or the like. The force transmission block 138 is a rectangular parallelepiped in a plan view and has a width of about 1.0 mm and a height of about 0.5 mm. The force transmission block 138 is preferably made of an insulating material. Examples of the insulating material suitable for anodic bonding include borosilicate glass and glass containing mobile ions such as crystallized glass. Also, the force transmission block 138
May be formed of a silicon substrate or the like having an insulating film formed on the surface thereof.

The semiconductor substrate 122 (including the second semiconductor layer 126), the insulating layer 124, and the first semiconductor layer 122 described above are preferably formed of a silicon substrate of an SOI substrate, a silicon oxide layer, and a silicon active layer, respectively.

The width L1 of the first semiconductor layer 126 forming the protrusion 130 shown in FIG. 2 is about 10 μm. The width (thickness) L2 of the second insulating layer 128 is about 0.1 μm. Therefore, the width L3 of the protrusion 130 is about 10 + 0.1 × 2 = about 1
It is 0.2 μm. The height L7 of the protrusion 130 is about 3 μm. On the other hand, the width L4 of the first insulating layer 124 and the second semiconductor layer 123 forming the base portion 134 is about 14 μm.
And the width (thickness) L5 of the second insulating layer is about 0.1 μm. Therefore, the width L6 of the base portion 134 is about 14 + 0.
1 × 2 = about 14.2 μm. In addition, the base portion 134
The height L8 is about 3.5 μm. The height L8 of the base portion 134 is preferably 3 μm or more. As described above, in the present embodiment, the width L1 of the first semiconductor layer 126 (about 1
0 μm), the width L4 of the first insulating layer 124 (about 14 μm
m) is about 4 μm wider. It is about 2 μm wide on one side.

The operation of the force detecting element 101 of the first embodiment will be described. For example, a positive voltage is applied to the electrode 132a shown in FIG. 1 to form an electrode 132a diagonally formed with the electrode 132a.
Ground c. It is assumed that the external force W acts on the top surface of the force transmission block 138 in this state. Then, the external force W is
The strain gauge section 12 in the protrusions 130b and 130d shown in FIG.
6b and 126d. Therefore, the strain gauge portions 126b, 126b,
The resistance value of 26d increases. On the other hand, the strain gauge section 126
The resistance values of a and 126c do not change.

The voltage V appearing at the output electrode 132b
_at132b is represented by the following expression (1). _{V at132b = V at132a × R of126c} / (R of126b + R o f126c) ... (1) _{where, V at132a} is the voltage value applied to the input electrode 132a. _{R o} f126b, R of126c each, strain gauge portion 126b, which is a resistance value of 126c. When the resistance value of the strain gauge portion 126b increases and the resistance value of the strain gauge portion 126c does not change, the output electrode 132
The voltage value V _at132b appearing at b decreases.

The voltage V appearing at the output electrode 132d
_{The at132d} is expressed by the following equation (2). _{V at132d = V at132a × R of126d} / (R of126a + R o f126d) ... (2) _{where, R of126a,} R _of126d, respectively,
It is the resistance value of the strain gauge portions 126a and 126d. The resistance value of the strain gauge section 126d increases, and the strain gauge section 12d
If the resistance value of 6a does not change, the voltage value V _at132d appearing at the output electrode 132d increases.

V _at132b and V _at132d described above
The strain gauge section 126b,
The amount of change in the resistance value of 126d can be obtained. Then, the magnitude of the applied external force W can be obtained from the amount of change in the resistance value of the strain gauge portions 126b and 126d. By obtaining the amount of change in these resistance values using the Wheatstone bridge, the sensitivity is high and the influence of noise and the like can be offset.

A method of manufacturing the force detecting element 101 of the first embodiment will be described with reference to FIGS. First, an SOI substrate as shown in FIG. 3 is prepared. The SOI substrate is formed by stacking a silicon substrate 122, a silicon oxide layer 124, and a silicon active layer 126. Next, the first resist layer 140 is arranged and masked on a predetermined region of the silicon active layer 126. Then, the silicon active layer 126 not masked by the first resist layer 140 is subjected to RIE (Reacti
Etching is performed until the silicon oxide layer 124 is exposed. As a result, first semiconductor layers (silicon active layers) 126b and 126d protruding from the top surface of the silicon oxide layer 124 are formed as shown in FIG.

Next, as shown in FIG. 5, the first semiconductor layer 1
26b and 126d and the silicon oxide layer 12 adjacent thereto
The second resist layer 142 is arranged so as to cover the mask 4 and masked. Then, the silicon oxide layer 124 not masked by the second resist layer 142 and a part of the silicon substrate 122.
Is etched by RIE or the like. As a result, as shown in FIG. 6, the second semiconductor layers 123b and 123d and the first insulating layers (silicon oxide layers) 124b and 124d protruding from the main surface 120s of the silicon substrate 122 are formed.

Next, the top and side surfaces of the first semiconductor layer 126,
The side surface of the second semiconductor layer 123 and the main surface of the silicon substrate 122 are oxidized by a thermal oxidation method or the like. As a result, FIG.
A second insulating layer (silicon oxide layer) 128 is formed as shown in FIG. As described above, the first semiconductor layer 126 and the second insulating layer 128 covering the first semiconductor layer 126 form the protrusion 130. In addition, the base portion 13 is formed by the second semiconductor layer 123 and the first and second insulating layers 124 and 128 covering the second semiconductor layer 123.
4 are configured. Next, as shown in FIG. 1 and FIG.
A force transmission block 138 made of an insulating material (such as glass) is attached to the top surface of the protrusion 130 (more specifically, the second insulating layer 128) by, for example, anodic bonding. Through the above steps, the force sensing element 101 shown in FIGS. 1 and 2 is manufactured.

In this manufacturing method, as shown in FIG. 5, the first semiconductor layer 126 and the silicon oxide layer 12 adjacent thereto are formed.
4 is masked with the second resist layer 142. Then, the unmasked silicon oxide layer 124 and the silicon substrate 1
22 is etched (see FIG. 6). Accordingly, the silicon oxide layer 124 that constitutes the base portion 134 and a part of the silicon substrate 122 can be continuously formed without changing the resist layer 142. Therefore, according to this manufacturing method, it is possible to prevent the electric current flowing through the strain gauge section 126 from leaking to the outside (for example, the silicon substrate 122) and to prevent the flexed force transmission block 138 from coming into contact with the force detection block 120. The structure that can be manufactured can be efficiently manufactured.

When the silicon oxide film forming the second insulating layer 128 is formed by the thermal oxidation method as described above, a film having good mechanical and electrical properties can be formed. Therefore,
It is possible to more effectively suppress the current flowing through the strain gauge section 126 from leaking to the outside. However, the silicon oxide film forming the second insulating layer 128 may be formed by, for example, the CVD method. Also, the force transmission block 138
The mounting method is not limited to mounting or anodic bonding, and may be fixed by bonding with solder or an adhesive, for example. In the above, the first and second semiconductor layers, the protruding portion, the base portion, the first and second semiconductor layers are formed.
The insulating layers have been described with the subscripts b and d, but the same applies to the subscripts a and c.

When an external force W acts on the force transmission block 138 and stress acts on the first semiconductor layer 126 and the like, the stressed portion is activated. As a result, the first semiconductor layer 12
The leakage of current from 6 to the outside easily occurs. However, in the force sensing element 101 of the first embodiment, the width L1 (about 10 μm) of the first semiconductor layer 126 allows the first insulating layer 12 to be formed.
4 width L4 (about 14μm) is about 4μm (about 2μ on one side
m) Wide. In addition, the first semiconductor layer 126 and the second semiconductor layer 1
The surface of 23 is covered with the second insulating layer 128. Therefore, even when the temperature is high, the current flowing through the first semiconductor layer 126 is exposed to the outside (for example, the second semiconductor layer 123, the semiconductor substrate 1
22, the force transmission block 138, etc.) can be suppressed. In particular, the current flowing through the first semiconductor layer 126 is
A so-called creeping leak phenomenon that leaks from the peripheral edge of the first semiconductor layer 126 to the second semiconductor layer 123 (semiconductor substrate 122) can be effectively suppressed. Furthermore, as described above, the SOI
When the force sensing element 101 is manufactured using the substrate 120, the first semiconductor layer 126 and the second semiconductor layer 123 become the first insulating layer 1.
Structures separated by 24 can be easily formed.

Conventional force sensing element shown in FIGS. 11 and 12.
According to the structure of 1, the operating current (several mA) is about 10^-3~
10^-2(0.1% to 1%) leak current has occurred
It was On the other hand, the structure of the force sensing element 101 of the first embodiment
According to the operating current of 10 ^-6Below (nA order and below
The leakage current can be suppressed below. Therefore, the output electrode 13
The voltage value appearing at 2b and 132d changes depending on the leak current.
Strain gauge portions 126b, 126
It is possible to increase the detection accuracy of the amount of change in the resistance value of d.
It Therefore, the accuracy of detecting the magnitude of the applied external force W is high.
A force detection element can be realized.

Further, in this embodiment, the total height L7 of the protrusions 130 and the height L8 of the base portion 134 is 6 μm or more. As a result, even when a large external force acts on the force transmission block 138 and the force transmission block 138 hangs downward as shown in FIG. 2 and is deformed, the force transmission block 138 and the semiconductor substrate 122 (second insulating layer 128).
It is possible to avoid contact with. Therefore, even if a large external force acts on the force transmission block 138, it is possible to suppress a decrease in force detection accuracy or detection sensitivity.

(Second Embodiment) FIG. 8 shows a sectional view of a force detecting element 201 of a second embodiment. This cross-sectional view shows a cross section at a portion corresponding to the cross-sectional view of FIG. 2 (cross-sectional view taken along the line II-II of FIG. 1). As shown in FIG. 8, the force detecting element 201 of the second embodiment includes a force detecting block 220 and a force transmitting block 238. Although not shown, as in the first embodiment, four protrusions are provided, and four electrodes electrically connected to the strain gauges in the protrusions are also provided. Projections 230b, 230d
Protrude from the top surface of the first insulating layer 224. The protrusions 230b and 230d are respectively formed on the first semiconductor layer 226.
b, 226d and a second insulating layer 228 that covers the top and side surfaces of the first semiconductor layers 226b, 226d. The force transmission block 238 has legs 239b, 2 extending from its main bottom surface.
With 39d. The bottom surfaces of the legs 239b and 239d are attached or fixed to the top surface of the protrusion 226 by anodic bonding or the like. The width of the first insulating layer 224 and the width of the silicon substrate 222 are equal. That is, the first insulating layer 224 is
It is formed over the entire upper surface of the silicon substrate 222. The width of the silicon substrate 222 is about 1.4 mm as in the first embodiment. The width of the first semiconductor layer 226 is about 10 μm as in the first embodiment.

A method of manufacturing the force detecting element 201 of the second embodiment will be described. First, the first semiconductor layer 226 is formed by the same process as the manufacturing process shown in FIGS. Further, the top surface and the side surface of the first semiconductor layer 226 are oxidized by, for example, a thermal oxidation method to form a second insulating layer 228 made of a silicon oxide layer. Further, as shown in FIG. 8, the force transmission block 2
The leg portion 239 is formed on the glass forming the part 38. Leg 2
As a method for forming 39, for example, a chemical processing method such as etching and removing the portion indicated by reference numeral 240 with hydrofluoric acid may be used, or it may be removed by cutting with sandblast, dicer or the like. It may be a physical / mechanical processing method. Next, the top surfaces of the protrusions 230b and 230d (second insulating layer 228) of the force detection block 220 and the bottom surfaces of the leg portions 239b and 239d of the force transmission block 238 are attached by, for example, anodic bonding. Through the above steps, the force sensing element 201 shown in FIG. 8 is manufactured.

In the force detecting element 201 of the second embodiment, the force transmitting block 238 is formed with the projecting portion 239, and the side portion 240 of the projecting portion 239 is recessed. Therefore, the force transmission block 238 may be formed without forming the base portion 134 like the force detection element 101 of the first embodiment.
When a large external force acts on the force transmission block 238
Can be prevented from coming into contact with the first insulating layer 224 (force detection block 220). However, even when the protrusion 239 is formed on the force transmission block 238 like the force detecting element 201 of the second embodiment, the protrusion like the base portion 134 of the force detecting element 101 of the first embodiment is provided. Of course, it is good.

(Third Embodiment) FIG. 9 shows a perspective view of a force detecting element 301 of a third embodiment, and FIG. 10 shows a sectional view taken along line XX of FIG. The force sensing element 101 of the first embodiment shown in FIG.
As described above, the four first semiconductor layers 126a ...
This is a structure in which a Wheatstone bridge is formed by 126d. On the other hand, the force sensing element 301 of the third embodiment shown in FIGS. 9 and 10 has a single gauge structure. In the present specification, the “single gauge structure” refers to a structure that is electrically connected to the strain gauge portion and that the electrodes for external terminal connection are only the first electrode and the second electrode. In this embodiment, only the first electrode 332a and the second electrode 332b are electrically connected to the strain gauge portion (first semiconductor layer) 326 (see FIG. 10) and for external terminal connection. The contents of this embodiment will be described in more detail below.

As shown in FIG. 9, the force sensing element 301 is
The support base 321, the force detection block 320, and the force transmission block 338 are provided. A base portion 334 projects from the main surface of the force detection block 320 (silicon substrate 322). The base portion 334 has an electrode pedestal portion 336a,
336b is connected. The protruding portion 330 protrudes from the top surface of the base portion 334. The width of the base portion 334 is wider than the width of the protruding portion 330. Electrodes 332a and 332b are electrically connected to one end and the other end of the first semiconductor layer (strain gauge portion) 326 in the protruding portion 330, respectively.

Lower support portions 364a and 364b project from the main surface of the force detection block 320. Lower support part 3
From the top surface of 64a, 364b, the upper support portion 360a,
360b is protruding. The width of the lower support portion 364 is wider than the width of the upper support portion 360. The force transmission block 3 is provided on the top surfaces of the protrusion 330 and the upper protrusions 360a and 360b.
The bottom surface of 38 is attached or fixed by a technique such as anodic bonding. As described above, the force transmission block 338 is attached to the elongated protrusion 330 and the upper support portions 360a and 360b arranged on both sides of the protrusion 330. Therefore, the force transmission block 338 is stably supported and fixed to the force detection block 320.

As shown in FIG. 10, the force detection block 32
The 0 base portion 334 includes a second semiconductor layer 323, a first insulating layer 324 that covers a top surface of the second semiconductor layer 323, and a second insulating layer 328 that covers a side surface of the second semiconductor layer 323.
The protrusion 330 includes a first semiconductor layer 326 and a second insulating layer 328 that covers a top surface and side surfaces of the first semiconductor layer 326.
Similar to the first embodiment, the first semiconductor layer 326 has a p-type impurity added to the n-type layer and functions as a strain gauge portion.

The top surface of the first semiconductor layer 326 is the (110) plane. The first semiconductor layer 326 has a piezoresistance coefficient of π.
It is arranged so as to change according to ₁₃ . The longitudinal direction of the first semiconductor layer 326 extends in the <110> direction. As described above, when the piezoresistive coefficient is π ₁₃ ′, it has the maximum sensitivity in the <110> direction of the (110) plane.

The lower support portions 364a and 364b respectively include the fourth semiconductor layers 353a and 353b and the third insulating layers 354a and 354a that cover the top surfaces of the fourth semiconductor layers 353a and 353b.
And a fourth insulating layer 358 that covers side surfaces of the fourth semiconductor layers 353a and 353b. Upper support 360a,
360b is the third semiconductor layer 356a, 356b, respectively.
And a fourth insulating layer 358 that covers top surfaces and side surfaces of the third semiconductor layers 356a and 356b. The third semiconductor layer 360a,
Unlike the first semiconductor layer 326, the 360b remains an n-type layer and does not function as a strain gauge section.

Also in the force sensing element 301 of the third embodiment, the width of the first semiconductor layer 326 is the same as that of the first embodiment, and the width (about 10 μm) of the first semiconductor layer 326 makes the first
The width (about 14 μm) of the insulating layer 324 is about 4 μm wide. It is about 2 μm wide on one side.

The operation of the force detecting element 301 of the third embodiment will be described. First, for example, the first electrode 332a shown in FIG. 9 is connected to a current source, and the second electrode 332b is grounded. It is assumed that the external force W acts on the top surface of the force transmission block 338 in this state. Then, the external force W is transmitted to the first semiconductor layer (strain gauge portion) 326 in the protrusion 330. As a result, the resistance value of the strain gauge portion 326 increases in accordance with the stress acting due to the external force W. Therefore, the first electrode 332
The voltage appearing at a increases as the resistance value of the strain gauge section 326 increases. Therefore, by detecting the increase amount of the voltage value appearing at the first electrode 332a, the strain gauge unit 326 can be detected.
The amount of change in the resistance value of can be obtained. Then, the magnitude of the applied external force W can be obtained from the amount of change in the resistance value of the strain gauge portion 326. As described above, in the third embodiment, the first electrode 332a functions as both the input electrode and the output electrode.

When the force sensing element 301 of the third embodiment has a single gauge structure, the change in the output value when a predetermined external force is applied can be increased as compared with the bridge structure. Therefore, the detection sensitivity of the applied external force can be increased.
Further, compared to the bridge structure, the force detection element 301 having a simple structure can be easily realized. Therefore, it is easy to simplify the manufacturing process. Particularly in the single gauge structure, there are two electrodes (electrode 332) that are connected to the strain gauge section and are connected to the external terminals.
a, 332b). When the number of electrodes for connecting the external terminals is two, it becomes easy to connect the external terminals and the electrodes without using a wire. If the connection can be made without a wire, the problems (difficulty in connection work, deterioration over time, etc.) caused by connecting the external terminal and the electrode with a wire can be avoided. Even when the two electrodes and the external terminals are connected by wires, the demerit of the wire connection can be reduced as compared with the case where the four electrodes and the external terminals are connected by wires.
The single gauge structure is not limited to a structure having only one strain gauge portion. Even when a plurality of strain gauge sections are provided, one end of each of these gauge section groups is commonly connected to the first electrode, and the other end of each gauge section group is commonly connected to the second electrode ( A structure in which a plurality of gauge portions are connected in parallel can be said to be a single gauge structure.

Specific examples of the present invention have been described above in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

The scope of application of the present invention is not limited to the above-mentioned crystal planes, crystal directions, and bridge configurations. That is, instead of the (110) plane, <110> direction, and <100> direction described above, another crystal plane or crystal direction may be used. For example, the (100) plane may be used as the crystal plane. (1
When the (00) plane is used, the amount of change in the resistance value of the strain gauge portion can be made relatively large, and further, integration is easy. (110) plane, <110> direction, <10
When the 0> direction is used, crystal planes or crystal directions equivalent to these may be adopted. Crystal planes or crystal directions equivalent to these are shown in Tables 1 to 3 of JP 2001-304997 A.

There is no particular limitation on the shape of the protruding portion described in the above embodiment. For example, the top surface of the protrusion may be inclined with respect to the main surface of the force detection block. In addition, the top surface of the protrusion may be curved. In addition, the side surface of the protruding portion may have, for example, a tapered divergent shape. Further, in the above-described embodiment, the convex projecting portion is described as an example, but the projecting portion may project in a stepped shape, for example.
Further, there is no particular limitation on the form in which the protrusion is arranged. For example, in the force detection element 101 shown in FIG. 1, the four projecting portions 130a to 130d are arranged in a square shape, but they may be arranged in a rhombus shape, or the projecting portions extending in a curved shape are circular. It may be arranged in a shape.

Further, the technical elements described in the present specification or the drawings exert technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technique illustrated in the present specification or the drawings can simultaneously achieve a plurality of objects, and achieving the one object among them has technical utility.

[Brief description of drawings]

FIG. 1 shows a perspective view of a force detection element of a first embodiment.

2 is a sectional view taken along line II-II of FIG.

FIG. 3 shows an explanatory view of a method for manufacturing the force sensing element of the first embodiment (1).

FIG. 4 shows an explanatory view of a method for manufacturing the force sensing element of the first embodiment (2).

FIG. 5 shows an explanatory view of a method for manufacturing the force sensing element of the first embodiment (3).

FIG. 6 shows an explanatory view of the method for manufacturing the force sensing element of the first embodiment (4).

FIG. 7 is an explanatory view of the method for manufacturing the force sensing element of the first embodiment (5).

8 shows a sectional view of the force sensing element of the second embodiment corresponding to the sectional view of FIG.

FIG. 9 shows a perspective view of a force detecting element of a third embodiment.

FIG. 10 is a sectional view taken along line XX of FIG.

FIG. 11 shows a perspective view of a conventional force sensing element.

FIG. 12 is a sectional view taken along line XII-XII of a conventional force detecting element.

FIG. 13 shows an explanatory view of a conventional method for manufacturing a force sensing element (1).

FIG. 14 shows an explanatory view of a conventional method for manufacturing a force sensing element (2).

FIG. 15 shows an explanatory view of a conventional method for manufacturing a force sensing element (3).

FIG. 16 shows an explanatory view of a conventional method for manufacturing a force sensing element (4).

[Explanation of symbols]

101: Force detection element 120: Force detection block 122: Semiconductor substrate 123: Second semiconductor layer 124: First insulating layer 126: First semiconductor layer (strain gauge portion) 128: second insulating layer 130: protrusion 132: electrode 134: Base part 136: Electrode base 138: Force transmission block

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Atsushi Tsukada             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. (72) Inventor Jiro Sakata             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. (72) Inventor Tokio Fujitsuka             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. F-term (reference) 4M112 AA01 BA01 CA41 CA42 CA44                       CA46 CA49 DA03 DA04 DA05                       DA06 DA11 DA18 EA03 EA06                       EA09 EA13 FA01 FA20

Claims (12)

[Claims] 1. A substrate, a first insulating layer, and a strain gauge portion are provided, the first insulating layer covers at least a part of a top surface of the substrate, and the strain gauge portion is a top portion of the first insulating layer. A force sensing element having a semiconductor material that is formed in a protrusion that extends along the surface and has a resistance value that changes according to the stress that acts, and the width of the first insulating layer is wider than the width of the strain gauge portion. . 2. The force detection element according to claim 1, further comprising a force transmission block that comes into contact with the top surface of the protrusion. 3. A base portion protruding from the main surface of the substrate, the base portion having a first insulating layer, the width of the base portion being wider than the width of the protrusion portion, and the protrusion portion being the first portion of the base portion. 3. The force sensing element according to claim 1, which extends along the top surface of the insulating layer. 4. The force sensing element according to claim 1, further comprising a second insulating layer that covers a top surface and a side surface of the strain gauge portion. 5. The force sensing element according to claim 4, wherein the second insulating layer further covers the top surface of the substrate at a position other than the base portion. 6. The force sensing element according to claim 4, wherein the second insulating layer is formed of a silicon thermal oxide film. 7. The substrate is SOI (Silicon On Insulator)
The substrate is formed of a silicon substrate, and the first insulating layer is S
The force sensing element according to claim 1, wherein the force sensing element is formed of a silicon oxide layer of the OI substrate and the strain gauge portion is formed of a silicon active layer of the SOI substrate. 8. The leg portion extending from the bottom surface of the force transmission block is further provided, and the top surface of the protruding portion is in contact with the bottom surface of the leg portion.
The force detection element according to any one of 1. 9. The first electrode and the second electrode are further provided, and the electrodes electrically connected to the strain gauge portion and for connecting the external terminals are only the first electrode and the second electrode.
The force detection element according to any one of 1. 10. The force detection element according to claim 1, further comprising a support portion of the force transmission block that does not include a strain gauge portion. 11. A method for manufacturing a force sensing element using an SOI (Silicon On Insulator) substrate having a silicon substrate, a silicon oxide layer and a silicon active layer, wherein a predetermined region of the silicon active layer is masked with a first resist layer. A step of etching the SOI substrate until the silicon oxide layer is exposed, a step of masking the unetched silicon active layer and the silicon oxide layer adjacent thereto with a second resist layer, and an unmasked silicon A method for manufacturing a force sensing element, comprising the step of etching an oxide layer and a silicon substrate. 12. S for oxidizing the surface of an SOI substrate
The method of manufacturing a force sensing element according to claim 11, further comprising the step of heating the OI substrate and the step of bringing the force transmission block into contact with the SOI substrate.