JPS5936835B2 - Semiconductor pressure/differential pressure transmitter - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a pressure/differential pressure transmitter that converts fluid pressure into an electrical quantity and generates a standard electrical signal, and in particular uses a strain plate made of a semiconductor single crystal in the pressure converting section. This invention relates to a semiconductor pressure differential pressure transmitter.

Generally, a semiconductor pressure/differential pressure transmitter is constructed as shown in FIGS. 1 and 2.

Fig. 1 is a vertical cross-sectional view of the diaphragm type semiconductor pressure/differential pressure sensor section, and Fig. 2 shows the semiconductor diaphragm type pressure/differential force sensor shown in Fig. 1 bonded and rotated to a pressure introducing member. FIG. 2 is a partial cross-sectional view of the pressure transmitter loaded. Here, the pressure conversion pellet 1 is provided with a strain diaphragm 2 in the center that causes distortion due to the pressure of the fluid, and normally this pressure conversion pellet 1 is made of an n-type silicon single plate of several Ωm. There is.

The pellet 1 has a silicon pedestal 3 having the same coefficient of thermal expansion.
and is fixed on the adhesive surface 4 by epoxy adhesive or glass adhesive. A wiring package terminal board 5 is disposed on the silicon pedestal 3, and a bond wire 8 is connected to the strain resistance layer 6, which is formed by diffusion on the strain diaphragm 2 made of, for example, silicon, through a metal wiring layer 7 made of Al or the like. wired together. Next, FIG. 2 will be explained.

The silicon diaphragm type pressure sensor shown in FIG. 1 is fixed to a pressure introducing member 21 at a surface 22 by epoxy or glass bonding. The pressure introduction member 21 is made of a metal, for example, INL metal, which has a coefficient of thermal expansion equal to that of the pressure conversion pellet 1 and the silicon pedestal 3 in the range of -30°C to +150°C, which is the operating temperature of the pressure sensor. The pressure introduction member 21 is airtightly screwed to the pressure transmitter main body 24 through a threaded portion 23 formed at the other end. The fluid pressure to be measured is
The pressure is transmitted to a thin metal flexible diaphragm 25 provided at one end of the inlet joint of the transmitter, and is transmitted via silicone oil 26 vacuum-sealed between the flexible diaphragm 25 and the pressure conversion pellet 1. It will be done. On the other hand, electrical changes in the pressure conversion pellet 1 due to fluid pressure are transmitted to a compensation circuit system (not shown) through a connector 2T connected to the package terminal 5. Here, the pressure transmitter main body 24 is made of a stainless steel metal material that is not corroded by the measuring fluid and the corrosive atmosphere outside, and has a coefficient of thermal expansion that is significantly different from that of the pressure conversion pellet 1 and the pressure introduction member 21. However, it is protected from the influence of the main body 24 by a constricted portion 28 provided at the intermediate portion of the pressure introducing member. Although the silicon diaphragm pressure sensor described above in FIGS. 1 and 2 has many advantages, it also has one drawback.

First, the advantage is that the pressure conversion pellet 1, the silicon pedestal 3, and the pressure introducing member 21 all have the same coefficient of thermal expansion within the operating temperature range of the device. Conventional sensors of this type have the disadvantage that the coefficient of thermal expansion is different between the sensor itself and the joint where pressure is actually introduced, and that strain is applied to the sensor during mechanical connection. In the embodiment shown in Fig. 2, a pressure introduction member having the same coefficient of thermal expansion as the pressure conversion element is used, and it also has a constricted part in the middle, so mechanical and thermal strain is blocked at this part. The influence of the mounting casing and the transmitter main body 24 is not transmitted to the pressure transducer element. The only major drawback is that glass bonding or epoxy bonding must be used to bond the pressure transducer element to the silicon pedestal and to bond the silicon pedestal to the pressure introducing member. The adhesive is used to maintain airtightness in order to properly apply fluid pressure to the pressure conversion element, and to bond the pressure conversion pellet 1 and the pressure introduction member 21.
It must serve two purposes in order to maintain electrical insulation. Both epoxy adhesive and glass adhesive have various problems as adhesives for fixing silicon diaphragm type pressure sensors. For example, epoxy adhesives are said to have problems in long-term corrosion resistance. Furthermore, in glass bonding, the melting and bonding temperatures are generally very high, 600 DEG C. to 700 DEG C., and therefore the metal wiring layer on the pressure conversion pellet is corroded, making the process difficult. In general, adhesive materials, whether epoxy or glass, have lower corrosion resistance when bonded at a lower temperature, and better corrosion resistance when bonded at a higher temperature.

In this respect, epoxy adhesives cannot be used at temperatures much higher than the maximum operating temperature of the sensor, and when the sensor is used at high temperatures, it has the disadvantage of lacking long-term reliability. pressure sensor,
In strain sensors, adhesive work is unavoidable in order to fix pressure-sensitive and strain-sensitive elements.

When a semiconductor, especially silicon, is used for the pressure-sensitive or strain-sensitive element, if a gold-silicon alloy method can be used for adhesion, the properties can be stabilized even during long-term high-temperature use. Since this method forms an adhesive layer by alloying silicon and gold at 370°C, it has far superior durability and creep resistance than epoxy adhesive. However, a major drawback of this bonding method is that electrical continuity occurs between the substrate of the silicon pressure-sensitive element and the metal to which it is alloy bonded. For example, assume that the silicon diaphragm type pressure sensor shown in FIG. 1 is bonded to a gold-silicon alloy. First, when adhering the pressure-sensitive beret 1 and the silicon pedestal 3, strong gold-silicon adhesion cannot be obtained unless the silicon oxide film 9 is removed from the adhesion area in advance. Therefore, the silicon substrate 1 of the pressure-sensitive pellet and the silicon pedestal 3 become electrically conductive through the gold-silicon alloy layer. Further, electrical continuity similarly occurs between the metal pressure introducing member 21 and the silicon pedestal 3 shown in FIG. 2 via the gold-silicon alloy layer. In silicon diaphragm pressure sensors, the silicon substrate is generally n-type, and the diffused resistance layer is p-type.
Since a mold is used, a Pn junction is formed between them.
In actual pressure measurement, a reverse bias voltage must be applied to this Pn junction to electrically insulate the p-type diffusion layer from the n-type substrate. Furthermore, the metal pressure introducing member must be at ground potential along with the casing to which it is attached. If the n-type substrate of the pressure-sensitive pellet is in conduction with the pressure introduction member, a forward potential may be applied to the Pn junction. In addition, when a part of the circuit system is at ground potential along with the casing in the sensor section, it is called two-point grounding, and cannot be used in measuring instruments that are standardized to two wires such as industrial pressure transmitters. . The present invention provides a semiconductor pressure/differential pressure transmitter that improves the above-mentioned drawbacks of the adhesive technology and has established high performance, high reliability, and long-term stability of characteristics.

Next, one embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 3 shows a cross-sectional view, and 31 is an n-type silicon single crystal substrate with a p-type diffused resistance layer 32 in the center, a pressure-sensitive diaphragm 33 in the center, and a thick peripheral part 34. The pressure sensitive pellet 35 is a package member in which a terminal 37 is embedded in the periphery with a hermetic seal or the like 36.
In the center of the package member, a pressure introduction member 40 having a flange-like water end 38 at one end and a pressure introduction window 39 extending therethrough is brazed or screwed to the package members 35 and 41 to maintain airtightness. has been done. The pressure introduction member 40 has a pressure measurement temperature range of, for example, -30°C to +12°C.
A metal having the same coefficient of thermal expansion as silicon at 0° C., such as INL metal or silicon, is formed. However, the material of the package member 35 does not need to be specified in particular. A pressure-sensitive pellet 31 is attached to the flange-shaped flat end portion 38 of the pressure introducing member 40 made of 1NL metal via a gold-silicon alloy 12.

On the other hand, the package member 35 has an insulating material 4 on the housing 44.
3 to be airtightly installed. By this mounting method, the pressure sensitive pellet 31 and the housing 44 are completely electrically insulated. By using this packaging method, the p-type diffusion layer 32 provided on the pressure-sensitive pellet 31 and the mesh terminal 37 for taking out to the outside can be aligned at the same height. The pressure-sensitive pellets can be wired by a thermal bonding method or an ultrasonic bonding method, similar to the packaging method.

As another embodiment, the pressure-sensitive pellet 31 and the housing 44 may be insulated by bonding the pressure introduction member 40 and the package member 35 with glass.

Alternatively, the pressure introducing member and the package member may be attached using an adhesive such as epoxy after providing a gap between them using an insulating material such as a polymeric insulating material such as glass, ceramic, or mica. That is, the feature of the present invention is that the pressure-sensitive pellet is bonded to the flange-shaped bottom of the pressure-introducing member with a metal-semiconductor alloy such as gold-silicon alloy, and the pressure-sensitive pellet and the pressure-introducing member are positively connected. electrical continuity between the pressure-sensitive pellet substrate and the housing, and electrical insulation between the pressure-sensitive pellet substrate and the housing at least between the pressure introducing member and the package member or between the package member and the housing to which the package member is attached. This is established by providing glass, ceramic, polymeric insulating material, insulating adhesive, or a combination thereof on one side.

By using this method, the hermetic seal terminal can be removed directly from the bottom of the flange while maintaining insulation from the casing. There are two advantages in that this process can also be omitted. Conventionally, processes such as exposure, n+ diffusion, and metal vapor deposition were indispensable for forming n-substrate electrodes.
By using the present invention, since the flange portion is alloy-bonded to the n-type substrate, all of these steps can be omitted.
Furthermore, the gold-silicon alloy adhesion improves corrosion resistance and creep characteristics. Furthermore, it is also effective when measuring minute pressures using a vacuum filter lens. When using a vacuum reflux lens, it is necessary to evacuate one side of the pressure-sensitive pellet, and it is impossible to maintain a vacuum for a long time unless the vacuum container is evacuated at a high temperature of 300° C. or higher. If epoxy was used to maintain the airtightness, high-temperature exhaust treatment would not be possible, and long-term vacuum maintenance would not be possible. In addition, the pressure introducing member is made of INL metal, which has the same coefficient of thermal expansion as the silicon pressure-sensitive pellet in the sensor operating temperature range, and since the wall is thin except for the bottom of the flange to which the pellet is bonded, the material of the package member may be selected. The pressure-sensitive pellets are insulated from the effects of thermal strain and mechanical strain during installation. A method for airtightly attaching the insulating material 43 shown in FIG. 3 may be, for example, by using ceramic as the insulating material, metalizing both ends of the ceramic, and brazing one end to the package member and the other end to the casing.

Alternatively, one side may be made of metal, this may be brazed to the housing, screws may be provided on the other side, and the screws may be airtightly secured to the screws provided on the package member. This screw and metalization can be reversed. Alternatively, the casing and the package member may be bonded to glass. In addition, in cases where high-temperature treatment is not particularly required, such as the high-temperature exhaust treatment when using a vacuum filter lens as mentioned above, a material such as mylar, etc., may be used between the package member and the housing. A gap may be provided using an insulating material such as a polymeric insulating material, glass/ceramic, or mica, and the gap may be attached using an adhesive such as epoxy.

[Brief explanation of drawings]

FIG. 1 is a structural sectional view of a conventional semiconductor pressure sensor, FIG. 2 is a partial sectional view of a pressure transmitter loaded with the semiconductor sensor of FIG. 1, and FIG. 3 is a structure of an embodiment of a pressure sensor according to the present invention. FIG. 31 is a pressure sensitive pellet, 32 is a p-type diffused resistance layer, 33 is a diaphragm, 35 is a package member, 36 is a hermetic seal, 37 is a terminal, 38 is a flange-like flat end, 39
4 is a pressure introduction window, 40 is a pressure introduction member, 42 is a gold-silicon alloy, 43 is an insulating material, and 44 is a housing.

Claims (1)

[Claims] 1. A pressure introduction member having a pressure introduction window in the center and having a coefficient of thermal expansion that is almost the same as that of a semiconductor, a package member having a plurality of lead terminals formed with a hermetic seal around the pressure introduction member, and the pressure introduction member. A semiconductor pressure-sensitive pellet of a first conductivity type that is adhered to the introduction member in an electrically conductive state and is attached so as to seal the pressure introduction window portion of the pressure introduction member, and a diaphragm portion of the semiconductor pressure-sensitive pellet. a plurality of strain gauges of a second conductivity type provided in the
means for wiring a metal wiring layer attached to the strain gauge, the wiring layer and the head of the hermetic seal terminal on substantially the same plane, and between the pressure introduction member and the package member or between the package member and A semiconductor pressure/differential pressure transmitter comprising an insulating member on at least one side between the package member and a casing to which the package member is attached.