JP2830092B2 - Electrostatic protection element for semiconductor device - Google Patents

Description

The present invention relates to an electrostatic protection element for a semiconductor device.

[Conventional technology]

As shown in FIG. 2, the electrostatic protection element of the conventional semiconductor device has a diode between the input / output signal wiring 11 and the high-potential power supply wiring 12 and between the input / output signal wiring 11 and the low-potential power supply wiring 13. However, no consideration is given to the arrangement between the diodes, and N
The minimum distance between the first type buried layer 3 and the second N type buried layer 4 and the P-type inversion prevention region 2 was generally equal.

[Problems to be solved by the invention]

As is well known, when a static electricity is applied from the outside, the static electricity protection element of the semiconductor device discharges the static electricity before the element in the semiconductor device responds to cause destruction or deterioration which causes a problem in circuit operation. The main purpose is to bypass and discharge. The above-mentioned conventional electrostatic protection element of the semiconductor device suppresses the voltage applied to the internal element by the following method.

(1) Reduce the parasitic resistance of the diode.

(2) Make the pn junction of the diode a high-concentration junction.

In the method (1), when a forward voltage is applied to the diode, a current of several hundred mA flows through the diode instantaneously, so that the diode terminal voltage is prevented from increasing due to parasitic resistance. .

The method (2) mainly reduces the reverse breakdown voltage of the diode when a reverse voltage is applied to the diode.

However, as a method of obtaining a sufficient electrostatic withstand voltage against a reverse voltage, the conventional method (2) increases the load on the input / output terminals in order to increase the parasitic capacitance of the diode. As a result, the input / output characteristics are reduced. There is a disadvantage of causing deterioration.

[Means for solving the problem]

The electrostatic protection element of the semiconductor device according to the present invention is formed on one main surface of a semiconductor substrate of one conductivity type, and has two opposite conductivity type buried layers surrounded by one conductivity type inversion prevention region, each having one electrode. And a second diode between the input / output signal wiring and the high-potential power supply wiring. The first diode and the second diode each have a reverse conductivity type buried layer and one conductive layer. The minimum distance from the mold reversal prevention area is different.

〔Example〕

 FIG. 1 is a sectional view of one embodiment of the present invention.

First and second parts constituting an electrostatic protection element of a semiconductor device
Are formed in a P-type silicon substrate 1 and surrounded by a P-type inversion prevention region 2. The N-type first buried layer 3 and the N-type second buried layer 4, Three layers,
N type first region having a concentration of 10 ¹⁵ to 10 ¹⁶ / cm ³ contacting 4 and 6a, 6b
And N-type second regions 8a and 8b having a concentration of 10 ¹⁹ / cm ³ or more, and P-type second regions 9a and 8b formed in N-type first regions 6a and 6b, respectively.
9b, the P-type first region 7 connected to each diode and the silicon substrate 1 is surrounded by the insulating region 5, and the N-type first region of the first diode is formed through an opening provided in the insulating film 10 covering the surface. The second region 8a is connected to the high-potential power supply line 12, the P-type second region 9a of the first diode and the N-type second region 8b of the second diode are connected to the input / output signal line 11, and the second diode The P-type second region 9b and the P-type first region 7 are connected to a low-potential power supply wiring 13.

In this embodiment, the minimum distance between the P-type inversion prevention region 2 around the first diode and the N-type first buried layer 3 is reduced, and the reverse withstand voltage of the junction between both regions is made smaller than the reverse withstand voltage of the second diode. Make it smaller. Then, when a discharge occurs from the high-potential power supply wiring 12 side to the input / output signal wiring 11 side, the N-type first region is at a lower voltage at which a current flows from the N-type first region 6a through the P-type second region 9a. A current flows from the buried layer 3 via the P-type silicon substrate 1 and the N-type second buried layer 4. For this reason, the voltage between the high-potential power supply wiring 12 and the input / output signal wiring 11 can be suppressed lower than before, and destruction or deterioration of the internal element can be suppressed. As a result, it is possible to provide a semiconductor device with an increased resistance to static electricity without increasing the parasitic capacitance of the input / output terminals, that is, while maintaining the conventional response speed of the input / output signals.

In the above embodiment, the P-type inversion prevention region 2 is separated from the N-type first buried layer 3, but this may be in contact.

Further, two junctions are connected between the input / output wiring 11 and the low-potential power supply wiring 13, but one of them may not be connected.

〔The invention's effect〕

As described above, according to the present invention, a sufficient electrostatic withstand voltage can be provided without increasing the load capacitance of the input / output terminals, so that there is an effect that both high speed and high reliability of the semiconductor device can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of the present invention, and FIG. 2 is a cross-sectional view of one example of a conventional electrostatic protection element of a semiconductor device. 1 ... P-type silicon substrate, 2 ... P-type inversion prevention region, 3
... N-type first buried layer, 4 ... N-type second buried layer, 5 ... insulating region, 6a, 6b ... N-type first region, 7 ... P-type first region, 8a, 8b ... N-type second region, 9a, 9b ... P-type second region,
10: insulating film, 11: input / output signal wiring, 12: high-potential power wiring, 13: low-potential power wiring.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 27/04 H01L 21/822 H01L 29/90 H05F 3/02

Claims (1)

(57) [Claims] A first conductivity type semiconductor substrate formed on one main surface;
A first diode and a second diode each having one electrode of two opposite conductivity type buried layers surrounded by one conductivity type inversion prevention region are provided between an input / output signal wiring and a high potential power supply wiring and a low potential power supply. In an electrostatic protection element of a semiconductor device provided between wirings, a minimum distance between the reverse conductivity type buried layer and the one conductivity type inversion prevention region is different between the first diode and the second diode. An electrostatic protection element for a semiconductor device.