JPS62151732A - Joining structure for diamond body to metal body - Google Patents

Abstract

PURPOSE:To certainly and easily join a diamond body to a metal bodies regardless of a change of atmospheric temperature by joining the diamond single crystal body or a diamond semiconductor to other metal bodies via metal films of titanium, platinum and gold laminated in order. CONSTITUTION:The diamond semiconductor 48 is formed on the top of the diamond single crystal body 47. As to the semiconductor 48, boron and phosphorus are mixed in the diamond as impurities. Then, the monocrystal body 47 and the semiconductor 48 are joined to other metal bodies 31, 52B and 52C respectively via the laminated metal films 61, 62 and 63 of the titanium, the platinum and the gold so that the coefficient of thermal expansion is enlarged in order by these. In this way, a difference in the coefficient of thermal expansion among the single crystal body 47, the semiconductor 48, the respective metal films 61, 62 and 63, and the metal bodies 31, 52B and 52C is made small and the breakage does not take place on a joint even if the atmospheric temperature is changed in a large way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a bonding structure for bonding a diamond core to a metal body, and in particular to a mounting structure suitable for use in a pressure detector constructed from a diamond semiconductor strain gauge. Regarding.

[Prior Art] Conventionally, 3i semiconductors have been widely used as semiconductors. By the way, since the band gap of Sl is as small as about 1.1 eV, its semiconductor properties disappear when the operating atmosphere exceeds about 150°C. On the other hand, diamond is 3i above.
Its bandgap is very large, about 5.5 eV, and it is expected that if it is used as a semiconductor, it will be able to withstand high ambient temperatures.

In addition, single crystal diamond has excellent electrical insulation properties and extremely high thermal conductivity, so it can be expected to exhibit excellent performance as a semiconductor substrate.

[Problems to be Solved by the Invention] By the way, one of the problems when mounting the above-mentioned diamond semiconductor element is the bonding between it and a metal body. This is because the coefficient of thermal expansion of diamond is approximately 2.3x10-
6/'C, which is very small, and joining this with other metals such as stainless steel (thermal expansion coefficient of approximately 15 x 10'/°C (100'C)) is difficult due to the excessive difference in their thermal expansion coefficients. Therefore, there is a risk of damage to the joint due to changes in ambient temperature.

SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to provide a bonding structure that can reliably and easily bond a diamond body and another metal body regardless of changes in ambient temperature.

[Means for Solving the Problems] The structure of the present invention will be described with reference to FIG.
It is joined to another metal body 31 via each metal film of No. 3.

Further, the semiconductor 48 includes at least titanium 61 and gold 63.
It is joined to other metal bodies 52B and 52C via each metal film.

[Function, Effect] In the above structure, the thermal expansion coefficients of titanium 61 and gold 63 are 8.8x10-6/'C, 9, and 1x10/'C, respectively.
'C114,2x10-6/'C (at 100°C), and the coefficient of thermal expansion is increased sequentially from the side of the diamond single crystal 47 or the diamond semiconductor 48, and the other metal bodies 31.52B, 52C (these The coefficient of thermal expansion is typically 1.5x10-6/°C (100°C). As a result, the diamond body 47.48,
Each metal film 61.63 and metal body 31.52B, 520
The difference in coefficient of thermal expansion between the two is small, and even if the ambient temperature changes significantly, the joint will not be damaged.

[Example] Hereinafter, an example in which the bonding structure of the present invention is used in a semiconductor strain gauge of a pressure detector will be described.

In FIG. 4, a mounting screw portion 11a is formed on the outer periphery of a small diameter lower end portion 11 of the cylindrical housing 1 of the pressure sensor.
The outer periphery of the intermediate portion 12 has a square surface with a screw hole. A connector 2 is fixed to the upper opening of the housing 1 by caulking. A sensing body 3 is necessarily provided within the lower end portion 11 of the housing 1 . The sensing body 3 is a stainless steel cylindrical body with one end closed and which forms a pressure point P. The large-diameter flange portion 31 at the closed end is brought into contact with the inner peripheral stepped surface of the housing 1, and its opening is connected to the lower end of the housing 1. It is a matter of position.

The center of the flange portion 31 of the sensing body 3 is made thin and serves as a diaphragm 311. A semiconductor strain gauge 4 whose structure will be described later is provided on the upper surface of the diaphragm 311. A ceramic substrate 5 is provided on the outer periphery of the flange portion 31.
A conductive paste is printed and fired on the upper surface of the substrate 5 to form a signal extraction electrode (circuit), and a metal post 51 is erected to be electrically connected to the extraction electrode.

Then, the semiconductor strain gauge 4 and the lead electrode of the substrate 5 are connected with a wire 52, and the metal boss 51 is connected to the lead wire 5.
3, it is connected to the pin 21 of the connector 2.

As shown in FIG. 2, the strain gauge 4 includes four strain gauges 4A, 4B, and 4C on a single rectangular diamond single crystal plate 47.
14D is formed. Each of the strain gauges 4A to 4D is made of a meandering linear diamond semiconductor film 48, and has a rectangular surface electrode 4f! They are sequentially connected to each other via 41, 42, 43, and 44. One end of wires 52A, 52B, and 52C152D is connected to each of the electrodes 41 to 44,
After all, the strain gauges 4A to 4D constitute a bridge circuit as shown in FIG.

As shown in FIG. 1, the diamond single crystal plate 47 is
It is located on the upper surface of the central part of the flange portion 31 of the sensing body 3, and metal films of titanium 61, platinum 62, and gold 63 are laminated sequentially from the side in contact with the entire lower surface of the single crystal plate 47. The gold film 63 is bonded to the flange portion 31 using a brazing material 49. In this state, the strain gauges 4A and 4B among the strain gauges 4A to 4D are located directly above the diaphragm 311 (FIG. 2).

The diamond semiconductor film 48 formed on the diamond single crystal plate 47 is a P-type semiconductor film containing boron (B) as an impurity. Each of the electrodes 41 to 44 formed on the semiconductor film 48 is constructed by laminating metal films of titanium 61, platinum 62, and gold 63 in order from the side in contact with the semiconductor film 48.

The strain gauge 4 is manufactured as follows. That is, the diamond single-crystal plate 47 is placed in a microwave CVD'W apparatus with areas other than the area where the semiconductor film 48 is formed masked, and methane (CH4), hydrogen, and a small amount (0.1 to 1100
A mixed gas of diphorane (82H6) of pp> is supplied.

The mixed gas is microwave (2450MHz in this example)
The single crystal plate 4 is decomposed and excited to become plasma, and the single crystal plate 4
A diamond semiconductor film 48 containing boron is deposited and grown on the diamond semiconductor film 7 . Thereafter, the metal films 61 to 63 are sequentially formed on the upper surface of the semiconductor film 48 and the lower surface of the single crystal plate 47 by vapor deposition or sputtering. Note that each of the wires 52A to 52D can be easily connected to the gold film 63 of each electrode 41 to 44 by wire bonding or the like. The wires 52A to 52D are made of gold.

The pressure sensor having the above structure has a threaded portion 1a of the housing 1.
is attached to the engine cylinder wall.

Cylinder pressure is introduced into the cylinder of the sensing body 3 and applied to its diaphragm 311 . diaphragm 311
deforms in response to the applied pressure, and the strain gauges 4A and 4B located directly above the strain gauges 4A and 4B are strained and their resistance values change greatly. At this time, the other strain gauges 4C and 4D do not generate strain because they are formed at positions apart from the diaphragm 31, and their resistance values do not change. Therefore, when power is supplied between terminals T1 and T2 in FIG. 3, terminal T3
, T4, a pressure signal corresponding to the above deformation amount, that is, corresponding to the cylinder pressure is obtained.

Such pressure detectors operate normally even in high temperature environments of about 500'C. This is because the band gap of 3i, which has been conventionally used in semiconductor strain gauges, is about 1.1 eV, whereas that of diamond is very large, about 5.5 eV, and it does not lose its semiconductor properties even at high temperatures.

By the way, the coefficient of thermal expansion of diamond is approximately 2.3x 10
In an atmosphere where the temperature is extremely small at '/'C (100°C) and the temperature changes are large, bonding between the diamond single crystal plate 47 and the diamond semiconductor film 48 constituting the strain gauge and other metals becomes a problem. Here, in the above-mentioned strain gauge, the single crystal plate 47 and the semiconductor film 48 are metallized with titanium, which has a coefficient of thermal expansion that increases sequentially from these sides.
The three layers of platinum and gold maintain consistency in thermal expansion, thereby preventing the strain gauge from being destroyed by sudden heating, such as when starting an engine. By the way, the thermal expansion coefficients of titanium, platinum, and gold are 8.8X10-6/'C19 and 1X, respectively.
10”/°C114, 2X10-6/°C (100
°C).

Also, the thermal expansion coefficient of stainless steel is approximately 15X10-6/'C (
100'C), which is representative of the coefficient of thermal expansion of metals in general.

The diamond single crystal plate 47 can also be used as a diaphragm. This is shown in FIGS. 5 and 6. In FIG. 6, an opening 31a is formed at the center of the flange portion 31 of the sensing body 3, and the strain gauge 4 having the above-mentioned structure is covered with the opening 31a. That is, in FIG. 5, titanium 61, platinum 62, and gold 6 are sequentially deposited on the lower surface of the single crystal plate 47 facing the periphery of the opening 31a from the side in contact with this.
3 are formed, and a gold film 63 is bonded to the periphery of the opening 318 using a brazing material 49. Thus, when a measurement pressure is introduced, the diamond single crystal plate 47 deforms in accordance with the pressure.

Such a structure also has the same effect as the above embodiment.

By the way, the above three-layer metal membrane protects the pressure sensor from relatively low humidity (
When used at temperatures of about 400'C), the platinum film can be omitted. Further, the electrode does not necessarily have to have a three-layer structure, and may use only a titanium film, but the above-mentioned three-layer structure in which the outermost layer is a gold film is preferable in order to easily connect wires.

The diamond semiconductor film 48 in each of the above embodiments may be made of diamond doped with, for example, phosphorus (P) to make it an n-type semiconductor.

Metal films of titanium, platinum, and gold can be produced by mixing each metal powder with a solvent such as Chilbionel to form a paste, printing a pattern on it, and then baking it in a hydrogen, nitrogen, or steam atmosphere, or by thermal spraying. It can also be formed by a method such as

As described above, according to the bonding structure of the present invention, a diamond body and another metal can be easily and reliably bonded, and a live conductor strain gauge that operates well in an atmosphere of high temperatures and large temperature changes, for example, can be realized. be able to.

[Brief explanation of drawings]

1 to 4 show one embodiment of the present invention, in which FIG. 1 is an overall sectional view of the strain gauge, FIG. 2 is an overall plan view thereof, FIG. 3 is a connection diagram of each strain gauge, and FIG. The figure is an overall sectional view of a pressure detector, and FIGS. 5 and 6 are an overall sectional view of a strain gauge and a pressure detector, respectively, showing other examples of the present invention. 1... Pressure detector housing 3... Sensing body 31... Francine part (other metal body) 31a.
...Opening 311...Diaphragm 4.4A, 4B, 4C, 4D...Strain gauge 41
．． 42.43.44... Electrode 47...
Diamond single crystal plate 48...Diamond semiconductor film 49...Brazing material 52.52A, 52B, 52C152D...Wire (other metal body) χ2 diagram Figure 5 Figure 63

Claims (7)

[Claims] (1) A diamond single crystal or a diamond semiconductor made of diamond mixed with impurities is bonded to another metal body through at least titanium and gold metal films sequentially laminated from the single crystal or semiconductor side. A bonded structure between a diamond body and a metal body. (2) A bonding structure between a diamond body and a metal body according to claim 1, wherein the diamond semiconductor is formed by mixing boron (B) or phosphorus (P) into diamond. (3) A bonding structure between a diamond body and a metal body according to claim 1, wherein a platinum film is interposed between the titanium film and the gold film. (4) A bonding structure between a diamond body and a metal body according to claim 1 or 3, wherein each of the metal films is formed by vapor deposition or sputtering. (5) A bonding structure of a diamond body and a metal body according to claim 1, wherein the gold film is bonded to another metal body by brazing or wire bonding. (6) The above-mentioned diamond semiconductor is a strain gauge formed on the above-mentioned single crystal diamond, and the above-mentioned single crystal is attached to a stainless steel diaphragm that constitutes a part of the pressure chamber wall of the pressure sensor via each of the above metal films. A bonded structure of a diamond body and a metal body according to claim 1. (7) The above-mentioned diamond semiconductor is a strain gauge formed on the above-mentioned single crystal diamond, and the above-mentioned single crystal is arranged so as to cover the opening provided in a part of the stainless steel pressure chamber wall of the pressure sensor. The bonding structure of a diamond body and a metal body according to claim 1, wherein the diamond body and the metal body are bonded to the edge of the opening via a film.