JPS58103635A - Semiconductor pressure transducer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a sapphire substrate as an insulating layer with a metal housing to form a large semiconductor pressure transducer.

Generally, when a pressure transducer using a piezoresistive element made of a semiconductor is packaged as a pressure sensor, it is necessary to provide some kind of electrical insulation between the pressure transducer and the metal housing.

Therefore, a diaphragm part was formed in the center by joining the peripheral part of a sapphire substrate on which an epitaxial layer was grown on the main surface, and a circuit pattern made of a piezoresistor was formed on this diaphragm part 0111 epitaxial layer. If formed, the fire substrate described above can be used as an insulating layer, and the insulating support structure can be simplified. In particular, if an epitaxial layer is also formed on the main surface of the sapphire substrate on the side that is to be bonded to the support, it is possible to use this to electrostatically bond to the support, making it possible to create a sharp diaphragm. becomes.

In the above structure, the piezoresistor is normally diffused or ion-implanted into the epitaxial layer.
p formed by John et al. 9. The surface of the circuit panel, including the leads, is usually covered with an oxide insulating layer. However, in such a configuration, the output may drift after the power is turned on due to the action of ions existing in the insulating layer. occurs. In particular, when using a housing in a mobile ionic medium such as a sealed liquid such as silicone oil, due to the movement of ions in this medium, it may take quite a long time after the power is turned on until a stable output is obtained. energization is required.

The present invention was made in view of the above circumstances, and its purpose is to simplify the insulating support structure by using a sapphire substrate as an insulating layer, and to reduce the output drift after power is turned on. KTo provides a solid state semiconductor pressure transducer, 6°.
In the present invention, the surface of the piezoresistor excluding the electrode portion is covered with a conductive layer via an insulating layer for surface protection. First, this conductive layer is electrically connected to the epitaxial layer surrounding the piezoresistor to provide an electrode. Furthermore, a shield plate is arranged on the insulation layer A4 via a sealing liquid so as to cover the piezoresistor, and the shield plate and the epitaxial layer and the conductor layer are set at the same potential.

That is, by covering the piezoresistor with the conductor layer,
Ions in the insulating layer under the conductor layer are fixed, and output drift due to movement of the ions is reduced. In this case, if an electrode is provided by electrically connecting the conductor layer and the epitaxial layer, for example, if the piezoresistor is P type and the surrounding epitaxial layer is N type, the conductor layer By biasing the PN layer to the highest positive potential in the circuit, it is possible to maintain the PNm combination in a stable reverse bias state. .

Furthermore, in semiconductor pressure transducers used in the filled liquid, output drift due to the movement of ions in the filled liquid is caused by non-uniform distribution of surface charge, non-uniform distribution of electric field double layer, semiconductor interface, internal and oxidation. This is thought to occur as the interaction with impurity ions contained in the insulating film changes over time. Therefore, to prevent this, the potential of the transducer surface in the filled liquid should be made relatively zero. However, by providing a shield plate as described above and maintaining the same potential as the surface conductor layer, the electric field therebetween can be made relatively zero.

Examples will be described below.

. Figure I41 is a sectional view showing one embodiment of the present invention.

In the figure, 1 is a sapphire plate, and 2 is a first sapphire substrate made of N-type silicon grown on the main surface of the sapphire substrate 1.
3 is an epitaxial layer formed on the surface of the piezoresistor made of P-type silicon, 4 is an electrode thereof, and 5 is an epitaxial layer formed on the surface of the piezoresistor 30 except for the electrode 40 portion and made of silicon 92 oxide. The insulating layer 6 is a conductive layer made of polysilicon formed on the surface thereof. 9, 1 is the 29th epitaxial layer made of N-type silicon grown on the other main surface of the fire substrate 1;
The support is made of 8-wire glass. The epitaxial layer T shown in FIG. 2 and the support body 8 are bonded by electrostatic bonding, and an anode electrode (not shown in the figure) shown in FIG. The center portion of the pre-zero fire board 1 that is not restrained by the support 8 constitutes a diaphragm portion 1a, and the piezoresistor 3 is disposed in this portion.

By providing the conductor layer 6 on the surface in this manner, output drift due to movement of ions inside the insulating layer 5 can be effectively prevented.

In addition, in this case, the piezoresistor 3 is made of P-type silicon, but when a piezoresistor made of P-type silicon is used as a round shape, the pressure-resistance glue is smaller than when NyfI is used. In the (100) plane and <110> direction, where the piezoresistance coefficient is maximum and the piezoresistance coefficient is the highest, outputs in both forward and reverse directions with good symmetry can be obtained.

FIG. 2 is a cross-sectional view showing another embodiment of the present invention, and the same or corresponding parts as in FIG. 1 are denoted by the same symbols, and detailed explanation thereof will be omitted. That is, in this embodiment, the conductor layer 6 is
The conductor layer 6 and the first epitaxial layer 2 are electrically connected to the first epitaxial layer 2, and a metallization M electrode 9 is provided.
It becomes possible to apply the A41 voltage.

Note that in FIG. 2, 10 is a bulk contact portion made of N-type silicon. Such a bulk contact part 10 is particularly useful when the GT epitaxial layer 2 is made of N-type silicon and a Schittky barrier is formed between it and the metallized electrode 9. This is necessary for rounding the parts into contact. Figure 3 is a cross-sectional view showing a more relaxed embodiment of the present invention, and the same parts as in Figure 2 are given the same symbols and detailed explanation thereof will be omitted. . That is, in this embodiment, a conductive shield plate 11 is arranged above the conductor layer 6, and a power source 12 supplies electricity to the conductor layer S and the first epitaxial layer 2 through the shield plate 11 and the electrode 9. ◎ By arranging the shield plate 11 and making it the same potential as the conductor layer 6 in this way, this converter can be used in a sealed liquid such as silico/oil. In other words, even if the space between the shield plate 11 and the conductor layer 6 is filled with silicone oil or the like, the electric field between the shield plate 11 and the conductor layer 6 is relatively zero. The ions inside can be immobilized, and the output drift caused by the movement of these ions can be reduced. In particular, in this case, since the circuit, including the first epitaxial layer 2, is biased to a high positive potential, the PH9 relationship between the piezoresistor 3 and the first epitaxial layer 2 is stable and reverse. While being kept in a biased state, the piezoresistor 3 is rounded into a shape taken by the shield plate 11 and the conductor layer 6 and the first epitaxial layer 2 with the same higher positive voltage, making it more stable. change is being measured.

In the nine embodiments described above, the shield plate 11 may also be used as an envelope for the entire converter, or a separate envelope (not shown) may be provided on the opposite side of the shield plate 11 from the sapphire substrate 1. A structure may also be adopted in which the space between the envelope and the shield plate 11 and 0 is also filled with the sealed liquid.

Further, it is preferable that the shield plate 11 is provided so as to cover the entire sapphire base [1] as in the ninth embodiment described above, but the area where the circuit elements, that is, the piezoresistive elements 3 are formed, should be covered as much as possible. If you install it so that it covers it, there will be a storm. 1! In the above-mentioned embodiment, only the case where the GTO epitaxial layer 2 is made of N-type silicon, the piezoresistor 3 is made of P-type silicon, and is round will be described. This is because when a P-type piezoresistor is used, it has the advantages described above, but the present invention is not limited to this. Of course, it is also possible to form a circuit board. In this case, it is desirable to use the epitaxial layer, the conductor layer, and the shield plate with the circuit biased to a large Ti member potential.

i9. In the above-mentioned embodiment of the round can, only the case where the support body 8 made of glass can be used will be described; however, the present invention is not limited thereto; The insulating support structure can be further simplified by directly fixing it to the metal support. In this case, the surface of the second epitaxial layer T is further coated with silicone dioxide or the like as a solid electrolyte at a high temperature. By providing an active insulating layer, electrostatic bonding can be carried out while applying a voltage using the insulating layer side as a cathode and the metal support side as a seed electrode.

As explained above, according to the present invention, a semiconductor pressure transducer in which a sapphire substrate is used as an insulating layer and a diaphragm is constructed by electrostatically bonding the sapphire substrate to a support body is provided. Reduces the output torque after power-on due to the movement of ions in the filled liquid,
It has the excellent effect of making it possible to obtain stable yields.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIGS. 2 and 3 are cross-sectional views showing other embodiments of the present invention. Fram portion, 2...first epitaxial layer, 3
...Bi"f resistor, 4...electrode, 5...insulating layer, 6...conductor layer, T...second epitaxial layer, 8...support Body, 9Φ・Φ number metallization 1
[Electrode, 111I+1...Shield plate, 12...Power supply Patent applicant: Yamatake Honeywell Co., Ltd. Recipient: Masaki Yamakawa (and one other person) Figure 1 ■'' Figure 2

Claims (3)

[Claims] (1) Semiconductor pressure conversion made by electrostatically bonding the periphery of a fire substrate with a semiconductor epitaxial layer on its main surface to a supporting restraint body and configuring a diaphragm in the center! In I, the epitaxial layer is formed on the main surface of the sapphire substrate opposite to the bonding surface with the support restraint body, and the epitaxial layer is formed on the main surface on the bonding surface side. a second Evita medium layer;
The epitaxial layer 11 has a piezoresistor formed of a semiconductor of a conductivity type different from that of the first epitaxial layer in the diaphragm portion, and a piezoresistor other than the electrode portion of the piezoresistor An insulating layer formed on the surface of and! A semiconductor pressure transducer comprising: a good conductor layer formed on the surface of the i&cough insulating layer. (2) In a semiconductor pressure transducer comprising a diaphragm formed in the center by electrostatically bonding the peripheral portion of a sapphire substrate having a semiconductor epitaxial layer on the main surface to a supporting restraint body, the epitaxial layer is formed on the sapphire substrate. a first epitaxial layer formed on the main surface opposite to the joint surface with the support restraint body, and a second epitaxial layer formed on the main surface on the joint surface side, The ml epitaxial layer has a piezoresistor formed of a semiconductor of a conductivity type different from that of the first epitaxial layer in the diaphragm part, and the piezoresistor except for the electrode part of the piezoresistor. an insulating layer formed on the surface of the insulating layer, a good conductor layer formed on the surface of the fishing insulating layer and electrically connected to the first conductor layer, and the first conductor layer and the conductor layer. A semiconductor pressure transducer characterized by comprising an electrode top for supplying voltage to the semiconductor pressure transducer. (3) In a semiconductor pressure transducer comprising a diaphragm and a ram in the center of a sapphire substrate having a semiconductor epitaxial layer on its main surface, the peripheral edge of the sapphire substrate is fixed to a supporting restraint body, and the epitaxial layer is A ninth epitaxial layer formed on the main surface of the sapphire substrate opposite to the bonding surface with the support restraint body, and a second epitaxial layer formed on the main surface on the bonding surface side. p1 Said happiness 1
An epitaxial layer is formed on the diaphragm part.
It has a piezoresistor formed of a semiconductor of a conductivity type different from the epitaxial layer of the piezoresistor, and an insulating layer formed on the surface of the piezoresistor except for the electrode part of the piezoresistor, a conductive layer formed on the surface of the first epitaxial layer and electrically connected to the first epitaxial layer;
a round electrode for supplying voltage to the epitaxial layer and the conductor layer; and a shield plate with good conductivity, which is placed opposite the conductor layer with a filler liquid in between so as to cover at least 1 minute of the piezoresistor portion. A semiconductor pressure transducer comprising: the shield plate, the conductor layer, and the first epitaxial layer being at the same potential.