JPS60202343A - Complementary type semiconductor humidity sensor - Google Patents

Abstract

PURPOSE:To offset the fluctuation in characteristics due to dispersion caused in manufacturing, by forming insulated gate type field effect transistor elements, which are to become a humidity sensor, at neighboring positions on a substrate, and arranging gate electrodes at symmetrical positions to each other. CONSTITUTION:On a P type substrate 1, N type diffused layers 2 and 2 and 5 and 5, which form source and drain regions, gate electrodes 4a and 4b and gate insulating films 3 and 3 are formed. Insulated gate type field effect transistor elements 11 and 12 are formed at two neighboring positions. The respective gate electrodes 4a and 4b of the elements 11 and 12 are arranged at symmetrical positions to each other. Parts of the gate insulated films 3 and 3 are exposed to external atmosphere. Thus a humidity sensor is formed. In this way, fluctuation in characteristics due to dispersion caused in manufacturing is avoided, and the humidity sensor characterized by excellent detecting sensitivity and reliability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a humidity sensor that has a structure similar to an insulated gate field effect transistor and detects ambient humidity from a drain current that changes depending on the ambient humidity.

Prior art When an electrode is formed on a part of the surface of an insulating thin film and a voltage of vG is applied, the potential V of the film surface at time t at a distance @x from the end of the electrode follows. Here, C is determined by the dielectric constant of the insulating film, and C is determined by the quality of the film, the surface condition of the film, and the ambient humidity. It is known that R monotonically decreases with respect to humidity, so if distances X and t are determined, ■ is uniquely determined by humidity. Therefore, in a known insulated gate field effect transistor, the gate electrode is formed so as not to overlap with either the source or the drain in plane, and the source or drain is formed at a distance X from the end of the gate insulator. Provide an impurity diffusion layer to cover the above part!
By exposing it to a constant atmosphere, it is possible to measure the change in the drain-source current IDS over time and determine the humidity.

That is, FIG. 1(a) shows the conventional n-channel MO8F.
A cross-sectional view of an ET-type humidity sensor, and FIG. 3(b) is a plan view. In FIGS. 1(a) and 1(b), n-type diffusion layers 2 and 5 forming north and drain regions, a gate electrode 4, and a gate insulating film 3 are formed on a P-type substrate l, and an end portion of the gate electrode 4 is formed. Let X be the distance lL'lf between the end of the drain region 5 and the end of the drain region 5. This element is connected to the circuit diagram shown in Figure 2.
IJI L, time t = 0 teVc ≧VDD ＞
When a voltage VG of VT (where VT is the threshold voltage of this element) is applied, the distance PilC from the end of the gate electrode 4 is
Since the potential distribution V(x, t) on the insulating film 3 at time t of x follows equation (1), it changes as shown in the graph of FIG. Then, at the position of distance
) changes approximately as shown in the graph of Figure 4・22
``''C・8 is a solution of the equation vT-vG ・・f°2V Kuronokuni, and on the other hand, since 几 has humidity dependence,
Humidity M is uniquely determined from tc.

However, the above distance or the dimensional accuracy in the manufacturing process of such a transistor, especially the overlay accuracy when forming the gate electrode and the impurity diffusion layer, will vary, and as a result, the device characteristics of the sensor and temperature will vary greatly. There is a drawback. Therefore, in order to improve the measurement variation, it is necessary to make the value of the distance There is a problem with this.

C.9 Object of the Invention An object of the present invention is to provide a humidity detection sensor that is excellent in detection sensitivity and reliability and has less variation in manufacturing characteristics.

21. Structure of the Invention According to the present invention, two sets of insulated gate field effect transistor elements serving as humidity sensors having the above-described structure are formed adjacent to each other on the same chip, and the gate electrodes of each A complementary semiconductor humidity sensor is obtained in which characteristics fluctuations due to manufacturing variations are canceled out using signals from the two transistor elements.

E, Example Next, the present invention will be explained by examples.

FIG. 5 is a sectional view of one embodiment of the present invention. In FIG. 5, two sets of insulated gate field effect transistor elements 11 and 12 forming a humidity sensor, similar to those shown in FIG. It is formed. Thus, the respective gate electrodes 4a, 4b of the elements 11, 12 are arranged and formed in symmetrical positions while adjacent to each other.

Effects of the Invention FIGS. 6(a) and 6(b) are plan views for explaining the effects of the present invention. With respect to the distance XQ between the gate electrode 4a and the drain region 5, which is the original design value shown in FIG. 6(a), due to the mask overlay error in the manufacturing process, the distance ), if a dimensional error of △X occurs, x of the left transistor element 11 =
x6+△x1 X of right transistor element 12: X
It becomes Q-△X. Therefore, by measuring the time Tc until the source-drain current ID8 starts flowing from these two elements, the term dependent on ΔX is eliminated, and characteristic fluctuations due to manufacturing irregularities are avoided.

[Brief explanation of drawings]

Figure 1 (a) is a cross-sectional view of a conventional semiconductor humidity sensor, Figure 2 (b) is a plan view, Figure 2 is the connection diagram of Figure 1, and Figure 3 is a time harameter showing the potential versus gate-drain distance. FIG. 4 is a graph showing the change in source-drain current with respect to elapsed time. FIG. 5 is a cross-sectional view of an embodiment of the present invention. FIGS. FIG. 5 is a plan view corresponding to FIG. 5 for detailed explanation; 1...P-type substrate, 2...source region,
3...Gate insulating film, 4...Par gate electrode, 5...Drain region, 11...Left side element, 12...Right side element. z 7 Atsushi 3 Figure z 4 Figure

Claims (1)

[Claims] Insulated gate field effect in which source and drain regions are formed on the whole surface side of a substrate of one conductivity type by selectively diffusing impurities of the opposite conductivity type, and a gate electrode is formed on the channel between the source and drain via an insulating film. It has a structure similar to that of a transistor, but a part of the gate insulating film is exposed to the external atmosphere, and a part of the gate electrode overlaps only one of the source/drain regions and overlaps the other. On the other hand, in a semiconductor humidity sensor formed at a predetermined distance, two sets of the insulated gate field effect transistor elements are formed adjacently on one substrate, and the gate electrode of each set is A complementary semiconductor humidity sensor characterized in that the sensors are arranged and formed at mutually symmetrical positions between the mating parts.