JPH02248826A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To facilitate the manufacture of an electrode at a high position accuracy by a method wherein an insulation film is provided between a semiconductor single crystal body and a metal film for an electrode and a contact hole is formed at a part of the insulation film to make a connecting section between the crystal body and the metal film. CONSTITUTION:An insulation film comprising a silicon oxide film 11 is formed on the side where output electrodes 6 and 7 are provided at a side part of a silicon single crystal body 1 and contact holes 12a and 12b are formed at a part where the electrodes 6 and 7 are arranged. Electrodes 4-7 comprising a metal film are formed almost entirely on the side thereof. Therefore, electric continuity between the crystal body 1 and input electrodes 4 and 5 is obtained entirely while that with the output electrodes 6 and 7 is obtained through fine holes 12a and 12b and a part alone where the holes exist serves as output electrode in substance. Then, a position accuracy available when the holes 12a and 12b are formed defines a position accuracy of the electrodes. This facilitates the production of an electrode with a high position accuracy.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an orthogonal semiconductor pressure sensor that detects compressive force by utilizing the piezoresistance effect (piezoresistance coefficient π63·) of a semiconductor single crystal, and its element. In order to easily form electrodes on the sides while ensuring positional accuracy,
An insulating film is sandwiched between a semiconductor single crystal and an electrode, and electrical continuity is obtained through a contact hole provided in the insulating film.

[Industrial application field]

The present invention involves applying a compressive force perpendicular to the crystal plane of the semiconductor single crystal while passing a current through a semiconductor single crystal having a piezoresistance coefficient of π63. The present invention relates to an orthogonal semiconductor pressure sensor that extracts a voltage output corresponding to a force, and particularly relates to an improvement in the electrode structure arranged on the side surface of the sensor.

[Traditional techniques]

4 and 5 are a perspective view and a horizontal cross-sectional view, respectively, of a conventionally proposed orthogonal semiconductor pressure sensor.

In the figure, a silicon single crystal 1 has an upper surface (1
10) For example, from a silicon wafer, the horizontal cross-sectional shape is approximately square so that the two pairs of side surfaces face at 45 degrees from the <001> direction and at 45 degrees from the <110> direction, respectively. It was cut out as a piece of silicon.

The silicon single crystal 1 is a high resistance material containing a low concentration of impurities such as boron, and for example, the length of one side in the horizontal direction is 1.
.mu.m, and the thickness is set to several tens to hundreds of .mu.m in consideration of impurity concentration and input resistance. An insulating pedestal 2.3 made of, for example, glass or ceramic and having a thickness of about III11 is bonded to the upper and lower surfaces of such silicon single crystal body 1.

Furthermore, a pair of input electrodes 4. made of metal such as aluminum are provided on two opposing sides of the rectangular parallelepiped element having a structure in which the silicon single crystal 1 is sandwiched between upper and lower sides by pedestals 2.3. 5 is formed by vacuum evaporation, plating, etc., and a pair of output electrodes 6 made of similar aluminum or the like are formed on other opposing sides that are orthogonal to the above-mentioned side surfaces (including cases where they are slightly deviated from orthogonal). .7 is formed in the same manner. However, while the input electrode 4.5 is formed covering most of the side surface of the silicon single crystal 1,
As is clear from FIG. 5, the output electrode 6.7 is formed with good positional accuracy across only a small part of the center on the side surface of the silicon single crystal l. This output electrode 6.
The portions 6a and 7a in contact with the silicon single crystal 1 of No. 7 are arranged so as to be located approximately at the center of the side surface, and the tolerance range for the error in the distance a from the side surface edge is strict about ±10 μm, and the width The width is set to be as narrow as several tens of micrometers.

In the pressure sensor having the above configuration, the silicon single crystal 1 cut out in the above direction has a piezoresistance coefficient π63. Silicon single crystal 1 through .3
When a compressive force is applied in the vertical direction, a voltage corresponding to the force is generated between the output electrodes 6 and 7, and pressure can be detected by detecting this voltage. For example 100-200
Suitable for high pressure detection of around kg/cTll. The principle of operation will be specifically explained below based on FIG.

When compressive force is applied in the vertical direction to the silicon single crystal 1 having the piezoresistance coefficient π63· as described above,
Mutually orthogonal resistance components RL and R of the silicon single crystal 1
By changing R, a voltage output corresponding to the compressive force can be obtained. That is, when no compressive force is applied, RL and RR are equal as shown in FIG. 6(a), so the current flows straight between the input electrodes 4.5 and the output electrodes 6.7 in the vertical direction. No voltage is generated between them. However, when a compressive force is applied, RL and RR change according to the force as shown in Figure 6b) and take on different values, so the current flows more easily to the smaller resistance component and the current Since the density distribution changes and the potential distribution changes accordingly, a voltage is generated between the output electrodes 6,7. Therefore, by detecting this voltage, the magnitude of the compressive force can be known.

[Problem to be Solved by the Invention] In the pressure sensor having the above configuration, as mentioned above, the resistance change of the silicon single crystal l due to compressive force has a directionality, and the electric potential distribution generated within the silicon single crystal l accordingly. Since the change in is detected by the output electrode 6.7, the portion 6a of the output electrode 6.7 in contact with the silicon single crystal 1 shown in FIG.
Very strict precision is required for the dimensions a and 'b required for forming 7a. That is, regarding the distance a from the side edge, the balance between the left and right sides is more important than the value itself, and if this balance is lost and the contact portions 6a and 7a are formed at positions shifted from each other, an offset voltage will be generated. Therefore, the value of a needs to be formed with high precision so that it is within an error of approximately ±10 μm with respect to the set value. In addition, the contact portion 6a
, 7a, in order to extract the output efficiently, it is necessary to detect the slight potential distribution of the silicon single crystal 1, but as the value of b increases, the intensity of the output decreases. , b can be said to be smaller.

Conventionally, to form an electrode pattern, a metal film is first deposited on the entire side surface of the device by vacuum evaporation or plating, then a mask is formed on the metal film, and etching is performed through this mask to selectively remove the metal film. By removing the metal film,
A predetermined pattern is formed. However, with this technology, the above-mentioned problem occurs on the side of the device? It is difficult to form a consistent electrode pattern with high precision, especially for the left and right output electrodes 6.
．． There has been a problem in that it is very difficult to ensure strict positional accuracy of the contact portions 6a and 7a of 7.

Furthermore, with the above-mentioned technology, since each element must be aligned and manufactured, manufacturing costs are high, and there are also problems in that the characteristics of each sensor vary widely.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide an orthogonal semiconductor pressure sensor in which electrodes can be easily formed on the side surfaces of the element while ensuring positional accuracy.

[Means to solve the problem]

The semiconductor pressure sensor of the present invention has a piezoresistance coefficient of π6.・
An insulating film is formed on the side surface of a semiconductor single crystal body having an insulating film, and a contact hole is formed in the part of the side surface where the insulating film is formed where the input electrode and the output electrode are to be placed, and each side surface including the contact hole is formed with an insulating film. A metal film is formed for input and output electrodes. Note that the input electrode needs to be placed so as to cover almost all of the above-mentioned side surfaces, and there are cases where an insulating film is not actually required on the input electrode side, but in such a case, the width of the input electrode is exactly This is substantially equivalent to providing a contact hole with a size corresponding to , and the present invention is intended to include such a case as well.

[For production]

As described above, when an insulating film is formed between a semiconductor single crystal and a metal film for an electrode, and a contact hole exists in a part of the insulating film, there is electrical continuity between the semiconductor single crystal and the metal film. is obtained only in the area where the contact hole is present. Therefore, the positional accuracy of the contact hole directly becomes the positional accuracy of the electrode, and even if the positional accuracy of the electrode metal film itself is low, it has no relation to the positional accuracy of the electrode.

Moreover, such contact holes can be formed with extremely high positional accuracy by forming an etching mask pattern using, for example, photolithography, which is a technology established in current semiconductor processes. can. That is, it becomes possible to easily form electrodes on the side surfaces of the element while ensuring high positional accuracy.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 are a perspective view and a horizontal sectional view, respectively, of a semiconductor pressure sensor according to an embodiment of the present invention.

In the same figure, as in the conventional case, the silicon single crystal 1 is (
110) surface is the top surface, and the <001> direction and <110
There are two pairs of side surfaces, each facing in the 45@ direction from the ) direction, and an insulating pedestal 2.3 made of glass, ceramic, or the like is bonded to the upper and lower surfaces. This bonding is possible by using techniques such as anodic bonding (electrostatic bonding), eutectic bonding, and glass bonding. The length of the silicon single crystal 1 in the horizontal direction is approximately 1 mm in each case, and the thickness in the vertical direction is approximately several tens to hundreds of μm depending on impurity concentration and input resistance. The horizontal dimensions of the silicon single crystal 3 are the same as those of the silicon single crystal 1, and the vertical thickness is about 1 mm.

Further, as is clear from FIG. 2, a silicon oxide film 11 with a thickness of about 0.5 μm or more is formed on the side of the side surface of the silicon single crystal 1 on which an output electrode 6.7, which will be described later, is arranged. It is formed.

Note that if there is no pinhole, the thickness may be 0.5 μm or less. Then, contact holes 12a and 12b each having a width of, for example, about 20 μm are formed in the silicon oxide film 11 at a portion where the output electrodes 6.7 (6a, 7a) as shown in FIG. 5 are to be arranged. There is.

Furthermore, a pair of inputs made of metal films such as aluminum or platinum are provided on two opposing sides of the rectangular parallelepiped element, which has a structure in which the silicon single crystal 1 is sandwiched between upper and lower sides by pedestals 2.3. An electrode 4.5 is formed, and a pair of output electrodes 6.7 made of the same metal film as above are formed on other opposing side surfaces that are orthogonal to the above-mentioned side surfaces (including cases where they are slightly deviated from orthogonal). is formed. Here, the input electrode 4.5 covers almost the entire side surface of the device including the side surface of the silicon single crystal 1, and the output electrode 6.7 covers the silicon oxide film 11 having the contact holes 12a and 12b. It is formed on almost the entire side surface of the element using a technique such as vacuum deposition or plating.

In the pressure sensor having the above configuration, electrical continuity between the silicon single crystal 1 and the input electrode 4.5 is obtained over the entire boundary between them as in the conventional case, while the silicon single crystal 1 and the output electrode 6 .7 can be obtained only through minute contact holes 12a and 12b. That is, in the case of the output electrode 6.7, only the portions where the width contact holes 12a, 12b provided at a distance a from the side edge are present are substantially equivalent to the contact portions 6a, 7a in FIG. This becomes the upper output electrode.

In this way, electrical continuity of the output electrodes 6.7 is obtained only in the portions where the contact holes 12a and 12b are present, so the positional accuracy when forming the contact holes 12a and 12b becomes the positional accuracy of the electrodes. The metal film itself does not require high positional accuracy or shape accuracy as in the past. However, when forming the metal films for electrodes on each side surface, precision is naturally required to prevent the metal films from shorting each other. The contact holes 12a and 12b can be formed with extremely high positional accuracy by forming an etching mask pattern using, for example, photolithography. Therefore, in particular, the output electrode 6.7 can be formed more easily than in the past while ensuring the strict accuracy required for the above-mentioned distance a and width, which are its substantial position and dimensions.

The operating principle of the pressure sensor of this example is the same as that of the conventional one, so its explanation will be omitted (see Figure 6).
.

Next, an example of a method for manufacturing the pressure sensor of this embodiment having the above configuration will be described below.

First, as shown in FIG. 3, for each boundary region of a large number of regions (silicon single crystal formation regions) 21 that become individual silicon single crystals in the silicon wafer 20, a region ( A through hole 23 is formed except for the contact hole forming region (22). This through hole 23 can be formed with high precision, for example, by using photolithography and etching techniques, or by using microfabrication techniques such as ultrasonic machining and laser machining.

Subsequently, a silicon oxide film 11 having a thickness of approximately 0.5 μm or more is formed on the surface of the silicon wafer 20, including at least the inner surface of the through hole 23, by thermal oxidation, CVD, or the like. Next, each silicon single crystal forming region 21 is cut along a cut line 24 set along the boundary to obtain an individual silicon single crystal 1. At this time, a silicon oxide film 11 having contact holes 12a, 12b is formed on the cut surface of each silicon single crystal body 1, as shown in FIG.

Thereafter, as shown in FIG.
A pedestal 2.3 is joined to the upper and lower surfaces of the element, and an input electrode 4.5 and an output electrode 6.7 are formed on each side of the element thus obtained.

When the pressure sensor is manufactured as described above, the oxide film 1
1 and contact holes 12a, 12b can be simultaneously formed in a large number of silicon single crystal formation regions 21 on the entire silicon wafer 20, so manufacturing costs can be kept extremely low, and the formation of each sensor Variations in characteristics can be made extremely small.

Moreover, the positional accuracy of the contact holes 12a, 12b is determined by the positional accuracy of the through hole 23, and since the through hole 23 is formed by the high precision microfabrication technology as described above, as a result, the positional accuracy of the contact holes 12a, 12b is determined by the positional accuracy of the through hole 23. Positional accuracy is extremely high.

Note that the size of the pressure sensor of the present invention is not limited to the above-mentioned dimensions, and various dimensions can be considered within the range in which pressure detection using the piezoresistance coefficient π63· is possible.

In addition, as a semiconductor single crystal, piezoresistance coefficient π63
・If the input current direction and the output extraction direction are perpendicular (or almost perpendicular), and the resistance changes directionally due to the compressive force applied in the vertical direction. Often, as mentioned above (11
0) is not limited to a silicon single crystal body cut out with the top surface.

Furthermore, as the insulating film formed between the silicon single crystal and the electrode, various insulating films such as a silicon nitride film can be used in addition to the above-mentioned silicon oxide film.

Furthermore, the above manufacturing method is just an example, and the present invention is not limited thereto.

〔Effect of the invention〕

According to the present invention, the positional accuracy of the electrode can be obtained by forming an insulating film having contact holes between the silicon single crystal and the metal film for the electrode. Little precision is required. Therefore, compared to the conventional method of achieving positional accuracy using a metal film for electrodes, while ensuring higher positional accuracy,
It has the advantage of being very easy to manufacture.

[Brief explanation of drawings]

1 is a perspective view of a semiconductor pressure sensor according to an embodiment of the present invention; FIG. 2 is a horizontal cross-sectional view of the semiconductor pressure sensor shown in FIG. 1 cut through a silicon single crystal 1; The figure is a plan view showing the process of processing a silicon wafer in an example of the method for manufacturing the semiconductor pressure sensor of the above embodiment, FIG. 4 is a perspective view of a conventionally proposed orthogonal semiconductor pressure sensor, and FIG. A horizontal sectional view when the semiconductor pressure sensor shown in the figure is cut at the silicon single crystal l part. Figures 6 (a) and (b) explain the operating principle of the semiconductor pressure sensor shown in Figure 4. This is a diagram for DESCRIPTION OF SYMBOLS 1... Silicon single crystal, 2.3... Pedestal, 4.5... Input electrode, 6.7... Output electrode, 11... Silicon oxide film, 12a, 12b... Contact hole.

Claims (1)

[Claims] A semiconductor single crystal having a piezoresistance coefficient π_6_3' (
A pedestal (2, 3) for compressive force transmission is connected to the upper and lower surfaces of 1), and a pair of input electrodes (4, 5) are connected to the two opposing sides of the pedestal (2, 3).
in the semiconductor pressure sensor having a structure in which a pair of output electrodes (6, 7) are respectively arranged on the other two opposing side surfaces perpendicular to the side surface, An insulating film (11) is formed, and a contact hole (12) is formed in the side surface where the insulating film is formed, where the input and output electrodes are desired to be arranged.
a, 12b), and metal films for input and output electrodes are respectively formed on each side surface including the contact hole.