JPH02237166A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To eliminate special consideration for insulation properties of a metal package and a semiconductor pressure sensor chip and to realize stable characteristics change of the pressure sensor by enclosing an area which functions as the pressure sensor and by providing a trench oxide film to insulate and isolate it electrically. CONSTITUTION:An oxide film 12 is formed on a first (100) silicon semiconductor substrate 11. An area which functions as a pressure sensor is formed on a second (100) N-type silicon semiconductor substrate 13 which is joined on the oxide film 12 through anode junction. A trench oxide film 15 is formed to enclose the area, and the area which functions as the pressure sensor is electrically insulated and isolated by the oxide film 12 and the trench oxide film 15. Therefore, a pressure sensor section is completely insulated electrically, and insulated by an oxide film which is an electrically ideal insulating material. Thereby, even if the assembly is carried out directly to a metal package, it is unnecessary to give any consideration for electrical insulation properties. Stability can be realized against characteristics change of the pressure sensor caused by disturbance such as heat or light in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor pressure sensor, and more particularly to one in which a portion of the semiconductor pressure sensor chip that functions as a pressure sensor is completely electrically isolated and insulated. It is.

[Conventional technology]

A semiconductor pressure sensor in which a semiconductor diffused resistance layer is used as a gauge resistance and a bridge circuit is constructed using this gauge resistance uses an N-type silicon substrate as a substrate, and a P-type diffused resistance layer is formed on this N-type substrate. It is generally manufactured by forming.

However, since this semiconductor pressure sensor chip is mounted on a metal package using Pb/Sn solder or Au/Si solder, the package and the semiconductor pressure sensor chip are electrically connected, and the semiconductor sensor chip and Special measures were required when insulation from the package was required. For example, in order to insulate the package, a metal package containing a semiconductor pressure sensor chip is sometimes further encased in a resin package. Additionally, in order to obtain insulation properties, the semiconductor pressure sensor chip is integrated with a pedestal made of virex glass, etc., and then this is mounted on a metal package. [Problem to be solved by the invention] As described above, in conventional semiconductor pressure sensors, it is difficult to electrically insulate the semiconductor pressure sensor chip from the package, but the root cause of this is that the semiconductor pressure sensor chip itself It was not electrically insulated.

This invention was made in order to solve the above-mentioned conventional problems, and aims to provide a semiconductor pressure sensor that can completely electrically isolate the pressure sensor section on a semiconductor pressure sensor chip. purpose.

[Means for solving intelligence problems]

The semiconductor pressure sensor according to the present invention is a semiconductor pressure sensor that utilizes the so-called piezoresistance effect of a silicon semiconductor, which causes a resistance change in response to pressure.
00) An oxide film is formed on a silicon semiconductor substrate, and a part functioning as a pressure sensor is formed on a second (100) N-type silicon semiconductor base bonded by anodic bonding on the oxide film, and the part functions as a pressure sensor. A trench oxide film is formed to surround the pressure sensor, and the portion functioning as the pressure sensor is electrically isolated by the oxide film and the trench oxide film.

[Effect]

In the semiconductor pressure sensor according to the present invention, the first
Since the semiconductor of the sensor is completely electrically isolated from the pressure sensor part, there is no need to worry about electrical insulation even if it is assembled directly into a metal package. Also, P.N.
Because it has superior insulation properties compared to junction separation, it is extremely stable against changes in pressure sensor characteristics caused by disturbances such as heat and light. [Example] An example of the present invention will be described below with reference to the drawings.

1 to 4 show a method of manufacturing a semiconductor pressure sensor according to an embodiment of the present invention, in which 11 is a first (1
00) Silicon semiconductor substrate, 12 oxide film, 13 second
(100) N-type silicon semiconductor substrate, 14 is a trench, 15 is a trench oxide film, l6 is an N-type island, 17 is a P-type gauge resistor, l8 is an A! It's the wiring.

Next, the manufacturing method will be explained.

11 in FIG. 1 is a first (100) silicon semiconductor, and since this first (100) silicon semiconductor 11 has the property of simply becoming a base, the crystal plane is (100).
Other than that, the conductivity type of silicon semiconductor is P type even if it is N type.
It can be any shape, and any thickness is suitable. Further, there is no particular restriction on the magnitude of specific resistance.

Next, as shown in FIG. 2, the first (100) silicon semiconductor substrate 11 is entirely oxidized, and an oxide film 1 with a thickness of 1 to 2 μm is formed.
Form 2. If necessary, it is also possible to further stack an oxide film thereon using CVD technology. Next, alkali metal ions such as Na ions and K ions are implanted into this oxide film 12 by ion implantation. Subsequently, the silicon semiconductor substrate is subjected to heat treatment to remove crystallographic defects generated in the oxide film 12 and to uniformly diffuse alkali metal ions into the oxide film.

Next, as shown in Figure 3, we used anodic bonding technology to create a film with a thickness of several hundred μm.
A second N-type (100) silicon semiconductor substrate 13 is bonded with an oxide film 12 interposed therebetween. The specific resistance of the second N-type (100) silicon semiconductor substrate 13 is preferably 2 to 7 Ω·mark.
Subsequently, the second N-type (100) silicon semiconductor substrate 13 is lapped off to a thickness of 10 to 20 μm.

Next, as shown in FIG.
Dry etching or wet etching is performed from the (100) silicon substrate side 13 until it reaches the oxide film 12 at the bonding portion. This trench 14 is filled with an oxide film 5 using CVD technology, and the oxide film 12 used for anodic bonding and the trench oxide film 15 form a conductivity type that will become the pressure sensor part of the N-type (100) silicon semiconductor substrate 13. is N
A shaped island 16 is separated and formed. Next, a P-type gauge resistor 17 is formed in this N-type island l6 by ion implantation and diffusion. After each P-type gauge resistor 17 is made into a bridge with Al wiring 18, from the first (100) silicon semiconductor substrate side 11, which is exactly the back side of the pressure sensor section,
A silicon diaphragm is formed by performing anisotropic etching of silicon using an alkaline etching solution such as KOH. At this time, if anisotropic etching is performed to reach the oxide film 12 previously used for anodic bonding, KO
Utilizing the rapid decrease in the etching rate of the oxide film 12 due to H, it can serve as an etching stopper.

In the manner described above, a semiconductor pressure sensor chip is completed.

In the semiconductor pressure sensor chip of this embodiment, the pressure sensor part is completely electrically insulated by the oxide film 12 and the trench oxide film 15, and after the chip is assembled into the metal package, the metal package and the semiconductor are assembled. There is no need to take special consideration regarding insulation with the pressure sensor chip.

In addition, since the pressure sensor part is insulated with an electrically ideal insulating material called oxide film, external disturbances such as heat and light can cause damage to the PN junction between the P-type gauge resistor and the N-type island. It is possible to avoid characteristic fluctuations such as fluctuations in the characteristics of the pressure sensor due to leakage current flowing out.

C Effects of the Invention] As described above, according to the semiconductor pressure sensor according to the present invention, the part that functions as a pressure sensor is
00) An oxide film formed on a silicon semiconductor substrate and a second (100) bonded to the oxide film by anodic bonding.
Since the pressure sensor section is electrically isolated from the trench oxide film formed on the N-type silicon semiconductor substrate so as to surround the pressure sensor section, the metal package and the semiconductor pressure sensor chip can be separated after the chip is assembled into the metal package. In addition, there is no need to take special consideration for insulation between the This has the effect of making the pressure sensor extremely stable even when the characteristics of the pressure sensor change due to disturbances such as the following.

[Brief explanation of drawings]

1 to 4 are explanatory views showing the manufacturing process of a semiconductor pressure sensor chip according to an embodiment of the present invention. 11...first (100) silicon semiconductor substrate, 12
... Oxide film, 13... Second (100) N-type silicon half 1 body base 1i, 14... Trench, 15... Trench oxide film, 16... N-type island, 17. ...P type gauge resistor, 1 day...A2 wiring.

Claims (1)

[Claims] (1) In a semiconductor pressure sensor that uses the so-called piezoresistance effect of a silicon semiconductor that causes a resistance change in response to pressure, an oxide film formed on a first (100) silicon semiconductor substrate; A second (100
) an N-type silicon semiconductor substrate, a portion functioning as a pressure sensor formed on the second substrate, and a portion formed in the second substrate surrounding and electrically connecting the portion functioning as the pressure sensor; A semiconductor pressure sensor characterized by comprising a trench oxide film for insulation isolation.