JPH0677502A - Force conversion element pattern - Google Patents

Abstract

PURPOSE:To enable anode bonding between a pressure detecting surface in a wafer state and a force transmitting part made of glass, and facilitate mass production of force conversion elements, in a force conversion element pattern which is arranged on an N-type semiconductor and has a plurality of P-type acceptor diffusion layers. CONSTITUTION:P-type acceptor diffusion layers 12 having a specified thickness are formed on the surface of an N-type donor diffusion layer 11. Electrodes 13a, 13b, 14a, 14b electrically connected with only the layers 12 via an insulating layer 15 are formed. Connection wires 17 for connecting the electrodes 13a, 13b, 14a, 14b are formed. When a plurality of the P-type acceptor diffusion layers 12 and a force transmitting part of a glass wafer are subjected to anode bonding, all of the P-type acceptor diffusion layers 12 are kept at nearly equal potentials which are higher than the potential of the N-type donor diffusion layer 11. As a result, a backward voltage is not applied across the N-type donor diffusion layer 11 and the P-type acceptor diffusion layers 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a force conversion element pattern, and in particular, a glass force transmission portion is anodically bonded to a plurality of P-type acceptor diffusion layers provided as pressure detection surfaces on an N-type semiconductor. It relates to a force conversion element pattern.

[0002]

2. Description of the Related Art Conventionally, a force conversion element has been known in which a (110) plane of a Si single crystal body controlled to have a predetermined impurity concentration is used as a pressure detection plane (Japanese Patent Laid-Open No. 2-36574).

The force conversion element described in the above publication has a pair of electrodes provided on the (110) plane so as to oppose + 45 ° from the <001> direction and an electrode provided at −45 °. And a pair of electrodes provided, one of which is an input electrode,
The other is provided as an output electrode.

When pressure is applied to the (110) plane of the Si crystal, the Si single crystal body is distorted. When strain occurs in the Si single crystal body, the resistance value between the electrodes changes due to the piezo effect. At this time, each electrode can be regarded as four terminals of the Wheatstone bridge circuit, and when a predetermined potential difference is applied between the input electrodes, the potential difference according to the pressure applied to the (110) plane is output electrode. It will occur in the meantime.

Further, as described above, since it can be considered that the pressure is detected by the piezoresistor connected to the Wheatstone bridge, the output fluctuation due to the temperature change of the force conversion element can be suppressed small. Thus, the force conversion element described in the above publication has a simple structure and also has a self-temperature compensation function.

By the way, in the case of converting the change of the resistance value into the voltage in this way, the detection accuracy is improved as the resistance value is larger because the current value which can be passed through the circuit is limited. For this reason, the force conversion element described in the above publication has a resistance value between the electrodes sufficient to satisfy the required detection accuracy, that is, S
In order to secure the sheet resistance of the i single crystal body, the thickness of the Si single crystal body is specified to be 50 μm or less.

However, handling a Si single crystal wafer having a thickness of 50 μm or less is very difficult in terms of physical distribution and work. Therefore, as a Si single crystal body wafer that constitutes a force conversion element, a diffusion type wafer is proposed in which a P-type acceptor diffusion layer is provided as a pressure detection surface on a Si single crystal body in which an N-type donor is diffused. ing.

This diffusion type wafer has a force conversion element pattern consisting of a plurality of P type acceptor diffusion layers and input / output electrodes provided corresponding to the respective diffusion layers on the (110) plane of the crystal. ing. Then, by appropriately setting the thickness of the diffusion layer of the P-type acceptor and the like, the impedance of the force conversion element can be set to several 100Ω to several kΩ. As described above, by using this diffusion type wafer, the difficulty in handling the wafer is solved, and it becomes possible to easily manufacture the force conversion element that generates a sufficient output with respect to the applied pressure.

On the other hand, S which constitutes such a force conversion element
On the (110) plane of the i single crystal body wafer, as described above, a force conversion element pattern including a plurality of pressure detection planes and input / output electrodes corresponding thereto is provided. Therefore, in order to make each pressure detection surface and the input / output electrodes constituting the force conversion element pattern function as a force conversion element, the pressure to be detected is detected by some method without interference with the electrodes. Need to be communicated to.

Therefore, conventionally, a block-shaped force transmission portion for transmitting the pressure to be detected is arranged on the pressure detection surface of the force conversion element. The force transmission portion is a main portion that determines the characteristics of the force conversion element, and is a portion that causes a large error in detection accuracy depending on the quality of the joint between the force transmission portion and the pressure detection surface.

For this reason, no adhesive or the like is used for joining the pressure detecting surface and the force transmitting portion because the joining quality is likely to vary. That is, the force transmission part is made of glass (metal oxide), and bonding is performed by anodic bonding, which is a known bonding method between glass and Si.

This anodic bonding is carried out by connecting Si to a positive electrode and glass to a negative electrode with Si and glass in contact with each other and applying a voltage of 600 to 1000 V between them. As a result, at the interface between Si and glass, the ionized Si and the ionized O from the glass are bonded to each other to obtain a uniform and stable bond.

[0013]

However, in the above-mentioned conventional force transducing element pattern, a glass wafer having a plurality of force transmitting portions is used for a plurality of pressure detecting surfaces and a plurality of force transmitting portions for the reason described later. Cannot be anodically bonded in a wafer state.

That is, when the diffusion type wafer having the force conversion element pattern and the glass wafer are to be anodically bonded, the P type acceptor diffusion layer which is the pressure detecting surface and the force transmitting portion are in contact with each other. A predetermined high voltage will be applied between and.

In this case, in addition to a high voltage being applied to the interface between the two, the high voltage sneaking through the N-type donor diffusion layer of the diffusion type wafer causes the P-type acceptor diffusion layer and the force transmitting portion in the vicinity to be connected. Is also applied during.

That is, with the N-type donor diffusion layer as the positive electrode and the P-type acceptor diffusion layer to which no voltage is applied as the negative electrode,
A strong high reverse voltage is applied to the PN junction interface, and this interface is subject to dielectric breakdown, making it impossible to perform the desired function as a force conversion element.

Therefore, in the anodic bonding of the pressure detecting surface and the force transmitting portion, a plurality of pressure detecting surfaces are cut out from the diffusion type wafer and a plurality of force transmitting portions are cut out from the glass wafer.
I had to do it after that. As described above, the conventional force conversion element pattern has a problem that the pressure detection surface and the force transmission portion cannot be anodically bonded in a wafer state, and mass production is difficult.

The present invention has been made in view of the above points, and makes it possible to perform anodic bonding between the pressure detection surface and the force transmitting portion in a wafer state, and to perform mass production of force transducing elements. It is intended to provide an element pattern.

[0019]

The above-mentioned problems are provided on the surface of a Si single crystal wafer in which an N-type donor is diffused, and are composed of a P-type acceptor diffusion layer and arranged in a predetermined pattern. In the force conversion element pattern having a plurality of pressure detection surfaces as a part of the configuration, by a force conversion element pattern having a connecting line electrically connecting each of the plurality of pressure detection surfaces and the other pressure detection surface. Will be resolved.

[0020]

According to the above structure, the plurality of pressure detection surfaces are electrically connected to each other by the connection line until the Si single crystal wafer is cut. Therefore, when a voltage is applied to one of the plurality of pressure detection surfaces, the voltage is also applied to the other pressure detection surfaces.

Therefore, in order to anodically bond a glass wafer having a plurality of force transmitting portions to the Si single crystal wafer,
When a high voltage is applied between the two, the potential of the pressure detection surface becomes higher than the potential of the N-type donor diffusion portion of the Si single crystal wafer. Therefore, in the Si single crystal wafer, no reverse voltage is applied to the PN junction interface, and anodic bonding between the pressure detection surface and the force transmitting portion in the wafer state is possible.

[0022]

EXAMPLES Next, in order to further clarify the constitution of the force conversion element pattern according to the present invention, description will be given based on appropriate examples. FIG. 1 shows a main part of a Si single crystal wafer having an embodiment of a force conversion element pattern according to the present invention.
Incidentally, FIG. 6B shows a cross section taken along the line BB in FIG.

In the figure, reference numeral 10 indicates a Si single crystal wafer of this embodiment. Reference numerals 11 and 12 denote an N-type donor diffusion layer and a P-type acceptor diffusion layer, respectively, which form the main body of the Si single crystal wafer 10.

The N-type donor diffusion layer 11 and the P-type acceptor diffusion layer 12 are layers formed by implanting an impurity of a predetermined concentration into a Si single crystal wafer, and the surface on which the P-type acceptor diffusion layer 12 is formed. Is the (110) plane of the Si single crystal.

As shown in FIG. 1A, a plurality of P-type acceptor diffusion layers 12 are provided on the (110) plane of the Si single crystal wafer 10. In these P-type acceptor diffusion layers 12, the output electrode forces 13a and 13b are opposed to the direction of + 45 ° from the <001> direction of the crystal, and −4.
Input electrodes 14a and 14b are provided opposite to each other in the direction of 5 °.

Each of these electrodes 13a, 13b, 14a, 1
4b is formed by evaporating aluminum or the like, and the insulating layer 15 is provided between the Si single crystal wafer 10 and the contact holes 16a and 16b. That is, each input / output electrode 13a, 13b, 14a, 14b
The Si single crystal wafer 10 is electrically connected only to the P-type acceptor diffusion layer 12.

At this time, the P-type acceptor diffusion layer 12,
Input / output electrodes 13a, 13b provided corresponding to the
Reference numerals 14a and 14b are main parts of the force conversion element, and are parts that convert a given pressure into a predetermined electric signal. That is, the P-type acceptor diffusion layer 12 constitutes a pressure detection surface and also constitutes a piezoresistor that bridge-connects the electrodes.

That is, when a predetermined voltage is applied between the input electrodes 14a and 14b and the P-type acceptor diffusion layer 12 is driven by direct current and pressure is applied to the P-type acceptor diffusion layer 12, distortion occurs, which causes piezo resistance. The resistance value between the electrodes changes due to the effect. Therefore, a potential difference according to the applied pressure is generated between the output electrodes 13a and 13b.

The full width of the electric signal output from the output electrodes 13a and 13b is a value determined by the resistance change amount of the P-type acceptor diffusion layer. Since the resistance change rate is determined as a physical property value, in order to obtain a resistance value sufficient to obtain the required resistance change amount, it is necessary to set the surface resistance value of the P-type acceptor diffusion layer 12 to a predetermined value or more. To be done. Therefore, in the Si single crystal wafer 10 of this embodiment, the thickness of the P-type acceptor diffusion layer 12 is controlled to a predetermined value, for example, 20 μm.

[11] of the Si single crystal wafer 10
The (0) plane has adjacent input / output electrodes 13a, 13b, 14
A connection line 17 is provided to connect the a and 14b to each other. Therefore, unless the Si single crystal wafer 10 is cut, all the input / output electrodes 13a, 13b, 14a, 14b formed on the Si single crystal wafer 10 are electrically connected.

In the force conversion element pattern of this embodiment, the connecting line 17 is provided along the dicing line for cutting each force conversion element from the Si single crystal body wafer 10, and the Si single crystal. (110) of body wafer 10
The above-described insulating film is provided between the surface and the surface. Therefore, when each force conversion element is cut out from the Si single crystal wafer 10 by dicing, the connection line 17 disappears and the conduction between the electrodes is released.

FIG. 2 is a diagram for explaining a manufacturing process of a force conversion element using a Si single crystal wafer. In the figure,
Reference numeral 20 denotes a Si single crystal wafer, which has an N-type donor diffusion layer 21 and a P-type acceptor diffusion layer 22 similarly to the Si single crystal wafer 10 described above. Also, reference numeral 30
Shows a base wafer bonded to reinforce the Si single crystal wafer 20 to obtain practical strength as a force conversion element.

The surface of the P-type acceptor diffusion layer 22 is
This is a portion that functions as the pressure detection surface 23 of the force conversion element. Further, as described above, in order to make the surface of the P-type acceptor diffusion layer 22 act as the pressure detection surface 23, it is necessary to provide a predetermined electrode on the (110) surface of the Si single crystal body wafer 20.

Therefore, in the case of actually detecting the pressure by using the force conversion element, a means for transmitting the pressure to be detected to the pressure detection surface 23 without interfering with the input / output electrodes is required. Therefore, in such a force conversion element,
Conventionally, a structure in which a block-shaped force transmission portion 24 is joined to the pressure detection surface 23 has been used.

In this case, the pressure detecting surface 23 and the force transmitting portion 24
The joint quality with the is one of the items that most affects the accuracy of the force conversion element. For this reason, it is necessary to obtain a stable joining quality, and an adhesive or the like is not used for joining the two, and the joining is performed by anodic joining which is known as a joining method of Si and glass.

Therefore, the force transmitting portion 24 is made of glass, and is formed as a glass wafer 40 as shown in the figure for improving productivity. This glass wafer 40 is made of Si
A force transmitting portion 24 is provided at a portion of the single crystal body wafer 20 corresponding to the pressure detecting surface 23, and all the force transmitting portions 24 are aligned so as to contact the corresponding pressure detecting surface 23.

In anodic bonding, Si and glass are brought into contact with each other,
A high voltage is applied between the two, and Si, which becomes positive ions at the interface, and O, which becomes negative ions, are bonded to each other. That is, the anodic bonding can be performed by applying a high voltage between the Si and the glass which are in contact with each other.

Therefore, in this embodiment, as shown in the figure, the positive electrode of the power source 50 is connected to the P-type acceptor diffusion layer 22 to be joined, and the force transmitting portion 24 of the glass wafer 40 to be joined is connected. The negative electrode of the power source 50 is connected to the immediately upper part of, and a voltage of about 600 to 1000 V is applied between the both.

By the way, when the conventional force conversion element pattern is formed on the Si single crystal wafer 20, that is, when the P-type acceptor diffusion layers 22 are electrically independent from each other, anodic bonding is performed. A large potential difference is generated between the P-type acceptor diffusion layer 22 to which the voltage is applied and the P-type acceptor diffusion layer 22 to which the voltage is not applied.

At this time, the potential of the N-type donor diffusion layer 21 increases as the electrons, which are carriers of the N-type donor diffusion layer 21, flow out to the P-type acceptor diffusion layer 22 to which the voltage is applied. That is, a high reverse voltage is applied to the PN junction interface between the P-type acceptor diffusion layer 22 to which no voltage is applied and the N-type donor diffusion layer 21. In this case, this reverse voltage causes dielectric breakdown of the PN junction, and obviously the desired performance as a force conversion element cannot be obtained.

On the contrary, as described above, in the Si single crystal wafer 10 of this embodiment, the connection line 17 is provided between the electrodes.
Connected by. Therefore, in order to perform anodic bonding, 1
When a voltage is applied to one P-type acceptor diffusion layer 12, almost the same voltage is applied to all P-type acceptor diffusion layers 12 via the connection line 17.

Therefore, no reverse voltage is applied between the N-type donor diffusion layer 11 and the P-type acceptor diffusion layer 12, and the PN in the Si single crystal wafer 10 is used for anodic bonding.
The junction is not broken down.

As described above, according to the force conversion element pattern of the present embodiment, anodic bonding in a wafer state is possible, which is impossible with the conventional force conversion element pattern. Therefore, the productivity of the force conversion element is remarkably improved, and it becomes possible to mass-produce the force conversion element while securing a stable yield.

FIG. 3 shows another embodiment of the force conversion element pattern according to the present invention. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

In the figure, reference numeral 60 indicates an Si single crystal wafer provided with the force conversion element pattern of this embodiment. The Si single crystal wafer 60 has the same configuration as the Si single crystal wafer 10 except that the configuration of the connection line 61 is different from the configuration of the connection line 17 described above.

That is, the connection line 61 is the input / output electrode 1 provided for each P-type acceptor diffusion layer 12.
Of the electrodes 3a, 13b, 14a, 14b, the input electrode 14a
It is a configuration to connect only. When a high voltage is applied to one of the plurality of P-type acceptor diffusion layers 12 for anodic bonding, the connection line 61 is applied to all P-type acceptor diffusion layers 12 similarly to the connection line 17 described above. Transmit voltage.

Therefore, also in the force conversion element pattern of this embodiment, dielectric breakdown of the PN junction in the Si single crystal wafer 60 due to anodic bonding is prevented, and the force conversion element can be mass-produced.

Further, in each of the above embodiments, the connection line connecting each P-type acceptor diffusion layer is configured to connect the electrodes provided to each P-type acceptor diffusion layer. It is not limited to this. That is, it is only necessary that the plurality of P-type acceptor diffusion layers formed on the Si single crystal wafer be electrically connected, and the P-type acceptor diffusion layers may be directly connected without the electrodes.

[0049]

As described above, according to the present invention, the plurality of P-type acceptor diffusion layers provided on the Si single crystal wafer are held at substantially the same potential, and the pressure detecting surface and the force transmitting portion are connected to each other. Even if anodic bonding is performed in a wafer state, the PN junction in the Si single crystal wafer does not cause dielectric breakdown. For this reason, it becomes possible to perform anodic bonding between the pressure detection surface and the force transmission portion in a wafer state, which has been impossible in the past, and the productivity of the force conversion element is remarkably improved.

Therefore, the force transducing element pattern according to the present invention has a feature that it enables mass production of the force transducing element and also maintains stable element performance during mass production.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a Si single crystal wafer provided with an embodiment of a force conversion element pattern according to the present invention.

FIG. 2 is a diagram for explaining a manufacturing process of the force conversion element.

FIG. 3 is a configuration diagram of a Si single crystal wafer provided with another embodiment of the force conversion element pattern according to the present invention.

[Explanation of symbols]

 10, 60 Si single crystal wafer 11 N-type donor diffusion layer 12 P-type acceptor diffusion layer 13a, 13b Output electrode 14a, 14b Input electrode 17 61 Connection line

Claims (1)

[Claims] 1. A plurality of pressure detection surfaces which are provided on a Si single crystal body wafer in which N-type donors are diffused and which are composed of a diffusion layer of P-type acceptors and are arranged in a predetermined pattern as part of the structure. The force transducing element pattern, wherein each of the plurality of pressure detecting surfaces has a connection line for electrically connecting the other pressure detecting surface.