JPH01183165A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To largely reduce a thermal distortion, to improve temperature characteristic and to improve reliability by forming wirings around a diffused resistor at a part formed with a pressure sensitive film of a semiconductor film in which its impurity concentration is enhanced. CONSTITUTION:Wirings around a diffused resistor 3 of a part formed with a pressure sensitive film 5 are not formed of a thin metal film having largely different thermal expansion than that of other part, but of a semiconductor film 11 in which its impurity concentration is enhanced. Thus, the thermal expansion coefficient of the part of the wirings becomes substantially equal to that of the other part thereby to substantially eliminate a thermal distortion. Further, since the impurity concentration is enhanced, the number of carriers capable of sufficiently performing a function as a conductor is provided, the temperature hysteresis of a zero point is largely suppressed, and characteristic change due to a temperature is extremely reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a semiconductor pressure sensor that detects pressure by utilizing the fact that the resistance value of a diffused resistor formed in a semiconductor substrate changes with the distortion of the semiconductor substrate. Regarding the configuration of

[Conventional technology]

FIG. 2 shows a general configuration of a semiconductor pressure sensor. (a) is a plan view, and (b) is a sectional view taken along the line AA in (a).

The pressure-sensitive chip 1, which is the main body of the semiconductor pressure sensor, is attached to the surface of a single-crystal semiconductor substrate 2 by thermal diffusion technology or the like to a single-crystal semiconductor substrate 2 of a conductivity type opposite to that of the single-crystal semiconductor substrate 2, for example, an n-type. Four p-type diffused resistors 3 are formed. An insulating film 6 is formed on these diffused resistors 3, and the diffused resistors 3 have metal thin film wiring 4 made of aluminum, for example.
are connected through holes provided in the insulating film 6, forming a bridge circuit.

The back surface of the region where the diffused resistor 3 is provided is made thinner to form a pressure-sensitive diaphragm 5 as a pressure-sensitive film.

FIG. 3 schematically shows the cross-sectional structure of the semiconductor pressure sensor. A diffused resistor 3 is formed on a silicon single crystal semiconductor substrate 2, and its surface is coated with silicon dioxide (5iO
The metal thin film wiring 4 formed on the insulating film is connected to the diffused resistor 3 through a contact hole 7, which is a connection hole formed in the insulating film 6 by photolithography. Furthermore, a protective film 8 is formed on this as well, and a pad part 9 that becomes a terminal is opened by photolithography.The pressure-sensitive diaphragm 5 of a semiconductor pressure sensor, such as a pressure-sensitive diaphragm, is formed on the back surface of the semiconductor substrate 2. As shown in FIGS. 2 and 3, a single crystal semiconductor substrate 2.
Insulating film 6. It has a 4-layer structure consisting of a metal thin film @ 4° protective film 8. Typically, each of these materials is monocrystalline silicon (
Si), silicon dioxide 7 (5i02), T-lumi-1-lam (AJ3), silicon nitride (5isNi)
), and there is a large difference in the coefficient of thermal expansion as shown in the table below.

In this way, when forming an element by overlapping materials with different coefficients of thermal expansion, the thickness of the single crystal semiconductor serving as the substrate for a normal semiconductor element (for example, a bipolar IC) is approximately 500 mm. The thickness of the single crystal semiconductor in the pressure sensitive diaphragm 5 of the semiconductor pressure sensor is as thick as ~550 μm (for a wafer diameter of 4 inches), and the stress due to thermal distortion caused by the difference in thermal expansion coefficient between each layer can be ignored. teeth,
It is extremely thin, approximately 100 μm thick, and the stress caused by thermal strain generated between each layer cannot be ignored. In particular, from the above table, silicon dioxide (5i02) and aluminum (AJ
) have two orders of magnitude difference in coefficient of thermal expansion, making it particularly easy for thermal strain to occur at the joint between the two, and as a result, the temperature hysteresis characteristic at the zero point, which is one of the important requirements for semiconductor pressure sensors, can be ignored. The disadvantage is that it cannot be kept as small as possible.

An object of the present invention is to provide a semiconductor pressure sensor in which the temperature hysteresis characteristic at the zero point is negligibly small.

(Means for solving the flatness problem) This invention does not make the wiring around the diffused resistor at least in the part where the pressure-sensitive film is formed a metal thin film whose thermal expansion is significantly different from other parts, but increases the impurity concentration. The semiconductor film is formed using a semiconductor film.

[Effect]

When the wiring around the diffused resistor is formed of a semiconductor film with a high impurity concentration, the coefficient of thermal expansion of the wiring part and the coefficient of thermal expansion of the other parts are almost the same, so that almost no thermal distortion occurs. Furthermore, since the impurity concentration is high, a sufficient number of carriers can be provided to function as a conductor.

〔Example〕

FIG. 1 is a sectional view showing the structure of an embodiment of the present invention, including a simple construction process. FIG. 1(a) shows a state in which a reverse conductivity type diffused resistor 3 is formed on the surface of a single crystal semiconductor substrate 2, and a contact hole 7 is opened in an insulating film 6 on the surface by IJ graphing technology. . (b) has a semiconductor film on it, for example, polysilicon (Po-6
y-8i) is shown in which a polycrystalline semiconductor film 11 is formed by CVD technology or the like. This polycrystalline semiconductor film 1
1 is electrically connected to the diffused resistor 3 through the contact hole 7, and the diffused resistor 3 is formed into a pattern so as to form a Wheatstone circuit. At this time, the polycrystalline semiconductor 11 is heavily doped to have the same conductivity type as the diffused resistor 3, and is provided with sufficient carriers to function as a conductor. (C) shows a state in which a pressure sensitive chip 12 as a semiconductor pressure sensor element is formed.

A metal thin film 14 is formed on the pad portion 13 as a connection terminal by vapor deposition or the like, a protective film 15 is formed thereon, and the pad portion 12 is opened.

A pressure sensitive diaphragm 5 is formed on the back surface.

The diaphragm portion 5 of the pressure sensitive chip 12 made in this manner is attached to a single crystal semiconductor substrate 2. Insulating film 6. The material of each film is single crystal silicon (Si), silicon dioxide (Si02), polysilicon (Po, gy-8i), silicon nitride (
Si3N4), polysilicon (Po4y-8
Since the coefficient of thermal expansion of i) is approximately 2XIO - Celsius, unlike A and I3, which are thin metal films, the coefficient of thermal expansion of i) is close to that of other films, so thermal distortion is less likely to occur due to temperature changes. , temperature hysteresis at the zero point is greatly suppressed, and changes in characteristics due to temperature are extremely small.

The present invention can also be applied to an integrated pressure sensor in which a pressure sensor and a signal processing circuit for calculating and amplifying its signal are formed on one pressure sensitive chip. In this case, a polycrystalline semiconductor film is used for the wiring of the pressure-sensitive diaphragm 5, and a metal thin film is used for the wiring of the signal processing circuit and the butt part.

〔Effect of the invention〕

According to this invention, the wiring around the diffused resistor formed in the pressure-sensitive film part of the semiconductor pressure sensor is configured to be formed of a semiconductor film with a high impurity concentration. Since the coefficients of thermal expansion of the materials used are almost the same, the occurrence of thermal distortion is greatly reduced, and a highly reliable semiconductor pressure sensor with no problems in temperature characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the configuration of an embodiment of the present invention;
FIG. 2 is a plan view and a sectional view showing the general configuration of a semiconductor pressure sensor, and FIG. 3 is a schematic sectional view showing the configuration of a conventional technique.

Claims (1)

[Claims] (1) In a semiconductor pressure sensor in which a pressure-sensitive film is formed by reducing the thickness of the back surface of the region on which the diffused resistance is formed of a semiconductor substrate on which a diffused resistance is formed, at least the portion where the pressure-sensitive film is formed. A semiconductor pressure sensor characterized in that wiring around the diffused resistor is formed of a semiconductor film with increased impurity concentration.