JPS6361944A - FET type sensor - Google Patents

Abstract

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

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention forms a sensitive material on an F'ET element such as an MO8 type or an MIS type, and detects a This invention relates to an FET type humidity sensor that amplifies and detects with a two-FET element.

(Prior art) A so-called FET type sensor is a type in which various sensitive films are formed on an FET element and electrical changes in the sensitive film are detected as changes in the gate action of the FIT by interaction with a detection object.
High input impedance and amplification m of ET elements
By using t, a high output sensor can be obtained. Also FE
T-elements have the advantage of being easy to downsize and reduce costs because a large number of elements are formed on the same base, and many proposals have been made in recent years. By the way, the conventionally proposed F
The structure of the ET sensor is as shown in Fig. 2 or 3.
[ is omitted. The reason why such an FET type sensor is preferable for use is as follows. Initially FET U
A type of sensor that is used by being immersed in an aqueous solution has been proposed, and in this case, a normal FET element is used as the FET element.

If the terminal of the gate electrode comes into contact with the aqueous solution, ejection becomes impossible. Therefore, as shown in FIG.
The T-element was devised. After that, F E
A proposal has been made to use a T-type sensor, a typical example of which is a humidity sensor, with a typical structure as shown in Figure 3.

By the way, FET type humidity sensors used in environments other than aqueous solutions include humidity sensors, gas sensors, infrared sensors, etc. However, with conventional structures, there are large variations in sensor characteristics, and in order to compensate, it is necessary to select elements or adjust circuits. This requires complicated means, and a method for solving this problem has been proposed in Japanese Patent Laid-Open No. 60-242354. Even this proposal does not sufficiently eliminate device variations.

(Problems to be solved by the invention) FET type sensors with conventional configurations have large variations in characteristics between elements, and as a result, element selection or adjustment circuits are required. There was a drawback that it could not be taken advantage of.

There have also been proposals to improve device variations.

At present, sufficient effects have not yet been achieved.

The present invention has been made based on the above background.
It is an object of the present invention to provide an FIT sensor suitable for high-volume production with extremely small element variations.

[Structure of the invention]

(Means for Solving the Problems) The FET type sensor of the present invention has a structure in which a sensitive element k that undergoes an electrical change due to physical or chemical interaction with a detection object is used.
In an FET type sensor including a W field effect transistor, the sensitive body is provided with at least one elaborate electrode for detecting electrical changes, and one of the electrodes is provided with a field effect transistor. A gate set inside? It is formed by connecting [.

(Function) The FET type sensor related to the present invention O is as described above <1 sensing element 01! 7) Kl and gate voltage ifj: Due to the connected configuration, variations in the elements can be reduced. Considering this, it can be seen that the electrical change in the sensitive body acts directly on the FET element-gate 11. On the other hand, in the conventional configuration, electrical changes in gate potential are transmitted through a passivation film (SiN film) in addition to the gate oxide film, and in this case, the electrical properties of the SiN film are important for FET operation. It can be seen that this is a factor. By the way, as a regular SiN film farmer.

Chemical Vapor Deposition
(CVD) method is used. Si created using this method
It is known that the stoichiometric ratio, torturability, and film thickness of the N film easily vary depending on the manufacturing conditions. As a result, it can be assumed that the mechanical properties of the SiN film can easily vary, and in the conventional configuration method, SiN is a major factor in the variation in FET type sensors that detect changes in the electrical resistance value or electrical capacitance value of the sensitive body. It depends on the membrane. That is.

In the configuration of the present invention, since the gate electrode in the FET and the single pole of the sensitive body are in contact with each other, they are not affected by changes in the electrical properties of the SiN film at all, resulting in small device variations. I think it has become.

(Embodiment) An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a structural sectional view of an FET type sensor according to the present invention. The PET element shown in FIG. 1 is a MOS type n-channel FET, and is formed using a p-type silicon substrate (1) K n
A type source (2) and drain (3) are formed, and a gate E-class film (Si film) (4) is formed on these surfaces. This gate and insulating film are the source (2).

A through hole is provided in the drain (3) section.

A gate electrode (5) made of polysilicon is formed on this gate insulating film, and a thick SiN film (6) is deposited on its upper surface. 8iN1g has source (2), drain (3)
), all the through holes are formed in the gate electrode (5) portion, and the electrode conductor film (7) is completely formed in these through holes.

Further, an electrode (8) for a sensitive body is formed by forming a through hole in the gate electrode 11 (5) and connected to the nine electrodes, and a humidity sensitive film (9) is formed on this electrode (8) for a sensitive body. )
The other electrode is formed on the humidity-sensitive membrane! (1
0).

The lower electrode for the sensitive body (8) is made of Tf by sputtering.

Next, Au was deposited and formed. A wet monochrome-sensitive film was obtained by curing an acrylic monomer (2-hydroxyethyl acrylate) with light to form a thin film.

Furthermore, the upper electrode (10) was created by Auft sputtering method.

〔Effect of the invention〕

The effects of the present invention will be explained based on the operation of a seven-point mechanism.

At the time of humidity production, a constant voltage V is applied to the electrode (10), and the potential VG of the four colors (8) is 1e)r of the humidity sensitive membrane and 2ca of the gate 1 compensation membrane. A rule.

This is because the electrode (8) connects the gate electrode (5).

VG directly acts as gate 4 pressure. If the humidity changes now, the exclusive use of the humidity sensitive membrane changes to OH, and the electrode (
The hawk position in 8) also changes to Vc. This Guo Gutoshi king also changes from VC to Va, and detects the humidity of rT. By the way, in the case of the number of grooves in a conventional device, the gate voltage 4 is affected by the capacitance V of the SiN film, in addition to the capacitance Ca of the gate oxide film.

This 8iNj capacitance CsN is the thickness of the film, a@ degree.

According to the Kagakusha 6 Ura ratio, t# changes and is easy to vary.In the present invention, the capacitance component of the SiN film is
During production, it is not affected at all and variations can be greatly reduced. Also, the 8iN film used as a passivation film.

When used as an FFT type sensor, it is exposed to Δ normal flame, and it can be expected that impurities and ions will get mixed into the SiN film and the electrical properties will change over time, but in the configuration of the present invention, Since the electrical properties of the SiN film are not used at all, it has an excellent structure in which long-term changes over time can be completely ignored.

[Brief explanation of the drawing]

Is Fig. 1 an embodiment of the present invention? FET type humidity sensor shown
The structural cross-sectional view, Figures 2 and 3 are of the conventional PET type sensor +
, fc is a purchase Ur side view. 1...Silicon substrate, 2...Source, 3...Drain. 4...Gate oxide film, 5...Gate electrode, 6...Si
N film, 7...Lead conductor, 8...Sensor lower part 4
．． 9...Sensor, 10...f5 electrode on the sensor. Agent: Kensuke Nori Chika, Patent Attorney, Kikuo Takehana

Claims (1)

[Claims] In an FET type sensor, in which a sensitive body that generates an electrical change due to physical or chemical interaction with a detection object is arranged on a field effect transistor, the sensitive body has a sensor for detecting the electrical change. 1. A FET type sensor comprising at least one electrode, one of which is connected to a gate electrode provided within a field effect transistor.