JPH0318227A - High-voltage pulse noise absorbing element - Google Patents

Abstract

PURPOSE:To eliminate a high-voltage pulse noise from the outside by dividing the opposite conductivity low-concentration diffusion layer, which is formed in contact with one conductivity type semiconductor substrate, into two parts and by bonding one conductivity type high--concentration diffusion layers and a gate electrode between the two parts. CONSTITUTION:A one conductivity type semiconductor substrate 1 and two low-concentration diffusion layers 2, 3 conductivity type opposite to that of the substrate are provided at distance L. After the substrate in the region 8 intermediate between the low-concentration diffusion layers is controlled to a specific concentration by ion implantation, etc., a separating thick film 7' is formed in the substrate. In the central parts of the low-concentration diffusion layers 2, 3 where no separating thick film 7 is formed, the same conductivity type high-concentration diffusion layers 4, 5 as the layers 2, 3 are formed so as not to protrude from the low-concentration diffusion layers 2, 3. A gate electrode 6 is provided on the separating thick film 7' and connected with the high-concentration diffusion layer 4 forming a source side electrode Vout. A drain side electrode VPP is connected with the high-concentration diffusion layer 5. Thus, a high-voltage pulse noise from the outside is removed effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to a high breakdown voltage output element of an open drain MOSFET of a MOS semiconductor integrated circuit, which is induced by the coupling capacitance of an external load circuit. This invention relates to an element that absorbs high voltage pulse noise.

Conventional technology Figure 3 shows an open drain type MOS conventionally used.
A diffusion resistance element, which is a part of a high-rigidity output element of an FET, is shown. Forming a low concentration diffusion layer 1o of the conductivity type opposite to the well diffusion layer 9 formed on or in the conductivity type semiconductor substrate,
In order to make contact with both ends of the substrate, a high concentration diffusion layer 11. 12 are attached, and are respectively connected to a high voltage output terminal vOUT and a high voltage power supply terminal ■PP having a fixed potential. FIG. 4 shows the equivalent circuit.

Problem to be Solved by the Invention 3. In FIG. 3, the voltage output to the vOUT terminal 11 changes from vDD to ■PP. Here, DD is the power supply voltage of the integrated circuit, and vPP is the voltage value of the high voltage power supply. The vOUT terminal 11 receives pulses and pulses parasitically generated from the rectangular wave of another adjacent OUT terminal due to the influence of stray capacitance on the wiring board of an external device such as a fluorescent display tube.
Affected by noise. For example, VDD=5V, VPP=
-30V, if the OUT terminal 11 is fixed at vPP potential, another OUT terminal 5 to -30v4
When it operates and generates a rectangular wave, theoretically a voltage of ■○UT = - 6 5 V 'J will be generated in a pulse form at the VOUT terminal 11, and the withstand voltage of the low concentration diffusion layer 1o is ~2 ．． X l V p p-Vr, Dl270■
degree is required. This withstand voltage is more than twice the voltage value of the high voltage power supply used. MOS is becoming increasingly miniaturized
LSI manufacturing technology is nearing its limits, and it is becoming difficult to solve the problem with manufacturing technology. If an element with an element withstand voltage of ~2×1■PP-vDD1 or less is used, the element will be destroyed due to the influence of pulse noise.The characteristics of this invention When the absolute value of the potential generated at the withstand voltage output terminal becomes larger than the absolute value of the high voltage power supply potential, the high voltage pulse noise absorbing element, which is an element that connects the high voltage terminal and the high voltage power supply terminal, is replaced with a conventional diffused resistor. It is installed in parallel with the element.

Function The high voltage pulse noise absorbing element according to the present invention has two terminals, a high voltage output terminal and a high voltage power supply terminal, as a source and a drain, and a gate is connected to the high voltage output terminal. The source, button, and drain have a structure that has a breakdown voltage of IVPP-VDDI or more with respect to the conductive semiconductor substrate 1 or the well formed therein. Assuming that the resistance of the conventional diffused resistance element is R, the resistance of the high voltage pulse noise absorbing element according to the present invention is r, and the threshold voltage is ■I, (1) Bvd in the case of ■DD>■OUT>vPP+v
<■PP-vDD 5. , −, r )) R ( R = 1ooxΩ) (2) vOU
When T<vPP+vI, Bvd20r ((R). Here, Bvd indicates the withstand voltage between the source and drain of the high voltage pulse noise absorbing element, and the source and drain are assumed to be P-type diffusion layers.

(1) is a case where the high voltage output terminal is in a normal operating state, and there is no conduction between the source and drain of the Sihals noise absorbing element.

(2) is a case where a pulse noise of less than ■PP occurs at the high voltage output terminal, and the Sibar noise absorbing element becomes conductive.

Example FIG. 1 shows an embodiment according to the present invention.

Two low-intensity diffusion layer regions 2 and 3 of the conductivity type opposite to the conductivity type semiconductor substrate 1 or the well diffusion layer 1 formed therein are set apart by a distance L, and the substrate is separated in the region 8 in the middle thereof. After controlling the concentration on the surface of the liquid to a certain concentration by ion implantation 6, 7, etc., the thick separation film 7 is
In the center of the two low concentration diffusion layer regions 2 and 3 where a thick separation film is not formed, a high concentration diffusion layer 4 and 5 of the same conductivity type as 2 and 3 is formed as a low concentration diffusion layer. It is formed so as not to protrude from areas 2 and 3. The low concentration diffusion layers 2 and 3 may be formed after the high concentration diffusion layers 4 and 5 are formed. A gate electrode is provided on the thick film at an intermediate position between the high concentration diffusion layers 4 and 5,
Connected to the source side electrode and vOUT terminal (high concentration diffusion layer 4).

The electrode on the drain side is a PP terminal (high concentration diffusion layer 6).

The threshold voltage at which this device operates is controlled by the low concentration diffusion region 2,
This is done using the distance L of 3 and the surface concentration of the area of 8.

FIG. 2 shows an equivalent circuit in which the element according to the present invention is added in parallel to a conventional diffused resistance element.

Effects of the Invention By using the element according to the present invention, it is possible to eliminate high voltage pulse noise due to coupling capacitance from an external load circuit by passing through the high voltage output element of an open drain MOSFET. As a result, it is possible to stabilize the characteristics of high-voltage output elements and improve reliability, making it possible to improve MOS LSI
can reduce manufacturing technology constraints.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing a pulse noise absorbing element according to the present invention, Fig. 2 is a circuit diagram showing a method of utilizing the present invention using an equivalent circuit, and Fig. 3 is a cross-sectional view showing a conventional diffused resistor. , FIG. 4 is a circuit diagram showing a conventional example using an equivalent circuit. 1... Conductivity type semiconductor substrate 1 or a weno diffusion layer formed therein, 2, 3... Low concentration diffusion layer of the opposite conductivity type to 1, 4, 5...・High concentration diffusion layer of conductivity type opposite to 1, 6...gate electrode, a...
Thick oxide film, 8...A region between the low concentration diffusion layers 2 and 30, 9...A conductive semiconductor substrate casing or a well diffusion layer formed therein, 10... ...Low concentration diffused layer of conductivity type opposite to 9, 11.12...High concentration diffusion layer of conductivity type opposite to 9, 11...■OUT terminal, 12... ...■PP terminal, 13...Thick oxide film, L...Distance between low concentration diffusion layers 2 and 3, r...Resistance of the element according to the present invention, R...
Resistance of conventional diffused resistor, ■OUT...High voltage output terminal voltage, terminal name, ■PP...High voltage power supply terminal voltage, terminal name.

Claims (1)

[Claims] A conductive type semiconductor substrate or two low concentration diffusion layers of the opposite conductivity type to the well diffusion layer formed therein are installed at a certain distance apart, and the substrate surface concentration in the intermediate region of the low concentration diffusion layers is set. After setting a certain concentration, a thick oxide film is grown in areas other than the center of the surface area of the low concentration diffusion layer, and a thick oxide film is grown in areas other than the center of the surface area of the low concentration diffusion layer where a thick oxide film is not formed. , high-concentration source/drain diffusion layers of the same conductivity type as this low-concentration diffusion layer are formed so as not to extend from the region of the low-concentration diffusion layer, and are placed at intermediate positions between the high-concentration source/drain diffusion layers. A gate electrode is installed on one thick oxide film, and the gate electrode is connected to a high concentration source/drain diffusion layer to form a high voltage output terminal. A high voltage pulse noise absorbing element characterized by having a structure as a voltage power supply terminal.