JP2982360B2 - Electrostatic field detecting element and electrostatic field measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In copiers, antistatic appliances and the like, the necessity of measuring an electrostatic image or profile is increasing. The present invention relates to an element and an apparatus which enable non-destructive high-speed and high-accuracy measurement of an electrostatic field or a profile of an electrostatic field using semiconductor technology.

[0002]

2. Description of the Related Art Conventional electrostatic field measuring devices include a voltage detector and an electric balance. In these, the charge distribution of the electrodes of the detector is changed by the electrostatic field, and the resulting Coulomb force is indicated by a pointer. These are merely meters and cannot be taken out as electrical signals. In addition, the spatial distribution of the electrostatic field cannot be measured due to the large size of the detection unit. Recently, LiNbO ₃ and BSO (Bi ₁₂ S
An electric field sensor utilizing the electro-optic effect of an optical crystal such as iO ₂₀ ) and an electric field sensor utilizing a change in alignment of a liquid crystal due to an electric field have been reported. In other words, they convert the change in light transmittance of the sensing element due to the electrostatic field into an electrical signal, and can measure the spatial distribution of the electrostatic field. The device is complicated and large.

[0003]

The conventional static electricity measuring device or electrostatic field sensor has a large detecting section, and cannot measure the distribution of the electrostatic field with high resolution. In other words, it is the optical properties of these materials that respond to an electric field in an electric field sensor using the electro-optic effect of an optical crystal or an electrostatic field sensor using the orientation phenomenon of a liquid crystal by an electric field. A light source and an image sensor are required. Therefore, the size of the detection unit becomes large, and at the same time, two conversion processes from the electric field to the transmittance and from the transmittance to the electric signal are required, so that the measurement error tends to increase.

[0004]

An electrostatic field detecting element is a source having a conductivity type different from that of a substrate formed on a semiconductor Si substrate.
A drain diffusion layer, an electrically floating gate electrode formed on a thin oxide film interposed between the two diffusion layers,
It consists of a dielectric film formed on the gate electrode. The thickness of the gate electrode is made sufficiently thicker than the oxide film just below the gate. The dielectric film focuses the electric field on the gate electrode, and is made of a material having a large relative dielectric constant.

The electrostatic field detecting device comprises a first common line connecting drains of the electrostatic field detecting elements arranged at a constant pitch, a field effect transistor connected to a source of the electrostatic field detecting element, A second common line connected to a source of the transistor; and control means for controlling application of a voltage to a gate electrode of the field effect transistor, wherein a signal current generated by the electric field detecting element is sequentially transmitted to the first or second common line. Output from the line.

[0006]

The floating gate electrode of the electrostatic field detecting element is in an electric field, and the charges in the gate electrode are polarized on the front and back surfaces. Since the thickness of the gate electrode is sufficiently thicker than the oxide film immediately below the gate, the semiconductor surface immediately below the gate is more strongly affected by the charge on the back surface of the gate, that is, the oxide film side of the gate, and the electric field acts on the semiconductor surface. The mold is inverted and the source and the drain conduct. The conduction resistance is a function of an external electrostatic field, and when a constant voltage is applied between the drain and the source, a detection signal can be output as a signal current with an electrostatic field of a certain threshold or more. In order to detect an electrostatic field as an analog value, the semiconductor surface immediately below the gate is depleted, so that a signal current proportional to the electric field can be output. Since the dielectric film provided on the gate electrode has a function of converging the electric field, the electrostatic field can be detected with high sensitivity.

The electrostatic field detecting device can obtain signals corresponding to the distribution of the electrostatic field in time series from the second common line by applying a voltage from the control means to the gate electrode of the field effect transistor for access. it can.

Further, by reducing the area of the electric field detecting element using the integrated circuit technology, it is possible to detect the distribution of the electrostatic field with extremely high resolution and high accuracy.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view (a) and a plan view (b) of an electrostatic field detecting element according to an embodiment of the present invention. A source diffusion layer 2 and a drain diffusion layer 3 of a conductivity type different from that of the semiconductor substrate 1 are formed on the substrate. The polycrystalline Si film 4 and the Al film 5 form a gate electrode of the electrostatic field detecting element,
It is electrically floating. The dielectric film 6 is for converging the electric field. The thin oxide film 7 is interposed between the gate electrode and the substrate 1. The thickness of the gate electrode is sufficiently larger than the thickness of the thin oxide film 7. The thick field oxide film 8 is formed to separate adjacent elements. The Al film 9 for wiring applies a voltage to the source diffusion layer 2 and the drain diffusion layer 3. The passivation film 10 protects the substrate.

In this embodiment, since an example of detecting an electrostatic field in the positive direction is shown, the conductivity type between the source and the drain is N-channel, the substrate is P-type, and the source and drain are N-type.

The polycrystalline Si film 4 is formed by a CVD method as in a well-known MOS process, and the Al film 5 is formed by a vapor deposition method. The dielectric film 6 is made of Si nitride, BiTiO ₃ or PZT.
And is formed so as to cover the gate electrode. To increase the electric field convergence effect, it is preferable that the dielectric constant is large and thick.

When the electrostatic field detecting element is inserted into the electrostatic field with the gate electrode facing forward, the charges in the gate electrode are polarized on the front and back surfaces. Since the thickness of the gate electrode is sufficiently thicker than the oxide film immediately below the gate, the semiconductor surface immediately below the gate is more strongly affected by the charge on the back surface of the gate, that is, the oxide film side of the gate,
The conductivity type of the semiconductor surface is inverted by the action of the electric field thereby, and the source and the drain are conducted.

In the case of the enhancement type, the conductance between the source and the drain increases as a function of the electric field due to the polarization charge above a threshold electric field determined by various characteristics of the semiconductor and the oxide film. It is non-conductive below the threshold electric field.

On the other hand, in the case of the depletion type, the source and the drain conduct even at zero electric field, and the conductance increases with the increase of the electric field, and the intensity of the static electric field can be detected in an analog manner. By applying a constant bias voltage between the source and the drain, a signal current proportional to the electrostatic field can be obtained from the source or drain terminal.

Hereinafter, the electrostatic field measuring apparatus will be described.
FIG. 2 is a circuit block diagram of an electrostatic field measuring device according to one embodiment of the present invention. The electrostatic field measuring device comprises a plurality of electrostatic field detecting elements 11 (11
a to 11e), access field effect transistor 12
(12a-12e), the first line 1 connected to the power supply
3. It comprises a second common line 14 commonly connecting the source electrodes of the access field effect transistors, and a scanning circuit 15 as a control means.

One electrode of each electrostatic field detecting element 11 is a first electrode.
And the other electrodes are connected to the drain of the access field effect transistor 12, respectively.
The output terminal of the scanning circuit 15 is connected to the gate electrode of the access field effect transistor 12 and
Are sequentially output from the signal output terminal composed of the second common line 14.

All of these elements can be formed on a semiconductor substrate at a high density by integrated circuit technology.
Resolutions higher than DPI are also possible. FIG. 3 is an operation timing chart of the electrostatic field measuring device.

The operation of the electrostatic field measuring device of the present embodiment will be described with reference to FIGS. When the clock pulse CK and the start signal ST are applied, the scanning circuit 15 operates to output scanning signals Y1, Y2,..., Yn from its output terminals.
Are sequentially conducted, and the signal current Is of the electrostatic field detecting element 11 connected thereto appears on the signal output line.

In FIG. 2, the first common line 1
3 is connected to the power supply line and the output signal is taken out from the second common line 14, but it is also possible to connect the second common line 14 to the ground and take out the output signal from the first common line 14. is there.

Since the device constituting the present apparatus can be constituted by a Si device, it can be operated at an extremely high speed.

[0022]

According to the present invention, the electrostatic field and the distribution of the electrostatic field can be detected very simply, at high speed, and with high resolution, and the industrial effect is extremely large.

[Brief description of the drawings]

FIG. 1A is a sectional view of an electrostatic field detecting element of the present invention. FIG. 1B is a plan view of the electrostatic field detecting element of the present invention.

FIG. 2 is a block diagram of the electrostatic field measuring device of the present invention.

FIG. 3 is an operation timing chart of the electrostatic field measuring apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Source diffusion layer 3 Drain diffusion layer 4 Polycrystalline Si film 5 Al film 6 Dielectric film 7 Thin oxide film 11a Static electric field detecting element 11b Static electric field detecting element 11c Static electric field detecting element 11d Static electric field detecting element 11e Static electric field Detection element 12a Field effect transistor 12b Field effect transistor 12c Field effect transistor 12d Field effect transistor 12e Field effect transistor 13 First common line 14 Second common line 15 Scan circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-74874 (JP, A) JP-A-60-147128 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/8247 G01R 29/12 H01L 29/788 H01L 29/792

Claims (7)

(57) [Claims] 1. A source / drain diffusion layer of a conductivity type different from that of a substrate formed on a semiconductor substrate, a thin oxide film interposed between the diffusion layers, and an electrically formed film formed on the thin oxide film. An electrostatic field detection element comprising a floating gate electrode and a dielectric film formed on the gate electrode. 2. The electrostatic field detecting element according to claim 1, further comprising a gate electrode made of Al or a stacked film of polycrystalline Si and Al, and having a thickness sufficiently larger than a thin oxide film. 3. The electrostatic field detecting element according to claim 1, wherein a conductive channel is formed between the source and drain diffusion layers when the external electric field is zero. 4. The dielectric film according to claim 1, wherein the dielectric film is BiTi.
An electrostatic field detecting element made of a ferroelectric such as O ₃ or PZT. 5. An electrostatic field detecting element according to claim 1, a first common line connecting a drain of the electrostatic field detecting element, and an electric field connecting a source of the electrostatic field detecting element to a drain. An electrostatic field detector comprising: an effect transistor; a second common line connecting a source of the field effect transistor; and control means for controlling application of a voltage to a gate electrode of the field effect transistor. 6. A first common line connected to a power supply voltage and a second common line for outputting a signal current of a source of the electrostatic field detecting element.
The electrostatic field detection device according to claim 5, further comprising: a common line. 7. The electrostatic field detecting device according to claim 5, further comprising a second common line connected to a ground potential, and a first common line for outputting a signal current of a source of the electrostatic field detecting element.