JPH01218041A - Protective element against static electricity - Google Patents

Abstract

PURPOSE:To eliminate a parasitic resistance and to perform sufficient protection against a breakdown due to static electricity by a method wherein a signal line is bypassed and an emitter electrode part of a protective element is connected to a lowest potential line directly by using a wiring part on an IC. CONSTITUTION:Signal lines L1, L2 are arranged and installed between a base electrode (B) and an emitter electrode (E) of a protective element composed of a bipolar transistor. The electrode (E) is connected directly to a ground line (G) by using a wiring part Ls. Accordingly, a parasitic resistance value r1 becomes nearly zero. The electrode (B) is connected to the ground line (G) through the inside of a substrate via a substrate connection part S3 and a substrate connection part S4; accordingly, a parasitic resistance value r2 is produced. The existence of the resistance value r2 is not so harmful. Accordingly, an excess voltage from the outside can be absorbed completely. By this setup, a sufficient protection against a breakdown due to static electricity can be performed.

Description

[Detailed Description of the Invention] [Summary] With regard to the arrangement of electrostatic protection elements for protecting internal circuits, the purpose of this invention is to improve the protection effect from electrostatic damage in a single-layer wiring master slice type semiconductor integrated circuit. A signal line is disposed between a base electrode and an emitter electrode of a protection element made of a bipolar transistor, and the emitter electrode and the lowest potential line are directly connected by wiring.

[Industrial Field of Application] The present invention relates to the arrangement of electrostatic protection elements for protecting internal circuits.

IC devices have become smaller and have lower withstand voltages, and are currently prone to electrostatic damage (electrostatic discharge).
Measures to protect against ``charge'' are becoming more and more important.

[Prior Art] Electrostatic protection is a method to prevent transistors inside an IC from being destroyed when an abnormally high voltage due to static electricity, for example, a high voltage of several hundred ports, is applied to input/output terminals (the input terminals will be explained below). The abnormal voltage is often received from a charged human body, and the human body is easily charged and can reach several thousand volts.

In order to prevent IC destruction due to such abnormally high voltage, various protection elements and protection circuit elements have been devised.
For example, the addition of resistors, diodes, and transistors, and combination circuits of resistors and diodes have been devised. In this method, such a protection element or protection circuit element is inserted between the external input terminal and the internal circuit, and the overvoltage is absorbed at the input terminal.

For example, in an analog mask slice IC, a protection element made of a bipolar transistor that has the same configuration as the internal circuit is provided. This is convenient for manufacturing. Figure 3 shows the circuit diagram of the protection element. is the external input terminal,
0 is the internal circuit input terminal.

T indicates a bipolar transistor, and +'l+'2 indicates a resistance parasitic to this protection element T.

On the other hand, since the internal circuits of mask-sliced ICs are designed according to the user's requests, the wiring on the IC surface can be patterned freely, and it is necessary to deliver the product as quickly as possible, which reduces the manufacturing process. For simplicity and inexpensive manufacturing, only single-layer wiring is provided on the IC surface, and multilayer wiring is usually not formed.

Figure 4 shows such a single-layer wiring analog mask slice I.
A plan view of a conventional protection element portion in C is shown, and C is a collector electrode portion of a transistor T.

B is the base electrode part, E is the emitter/7 electrode part, G is the ground line (lowest potential line) r L + + L2 is the signal line,
Pa is the bonding pad (external input terminal), Sl, S
2 is a board connection portion, and the other shaded portions are wiring lines.

Moreover, FIG. 5 shows a cross-sectional view taken along the line AA in FIG. 4, and the same parts as in FIG. , 3 is a P-type base region.

4 is an N+ type emitter region.

In this way, in analog mask slice IC,
A protection element made of a bipolar transistor is provided to protect against electrostatic discharge damage.

[Problems to be Solved by the Invention] By the way, the problem with the above structure is that the emitter electrode portion E is connected to the ground line G through the inside of the long substrate via the substrate connection portions S1 and 82. , therefore, the parasitic resistance r1 increases. This is clear by comparing the circuit diagram in Figure 3 and the plan view in Figure 4, but as a result, the absorption of externally applied overvoltage (electrostatic breakdown voltage) to the ground side is incomplete. Therefore, there is a drawback that the protection effect against electrostatic damage is not sufficient.

The present invention solves these problems and proposes an electrostatic protection element for the purpose of increasing the protection effect from electrostatic damage.

[Means for solving the problem] The purpose is to provide a signal line between a base electrode and an emitter electrode of a protection element made of a bipolar transistor, and to directly connect the emitter electrode and the lowest potential line with wiring. This is achieved by an electrostatic protection device.

[Function] In other words, in a single-layer wiring IC, due to the presence of a signal line, the emitter of the protection element and the lowest potential line (e.g., ground line) are connected by wiring (a wire with good conductivity). Therefore, it is connected to the lowest potential line through the board. Therefore, a large parasitic resistance r1 occurs.

The present invention is configured so that the signal line is detoured and the connection between the emitter electrode portion of the protection element and the lowest potential line is directly made by wiring on the IC surface. By doing so, the parasitic resistance r is almost eliminated, and protection from electrostatic damage becomes sufficient.

[Example] Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 1 shows a plan view of a protection element portion according to the present invention,
FIG. 2 shows a DD sectional view of FIG. 1. In these figures, the same parts as in Figs. 4 and 5 are given the same symbols, but other parts of s3. s4 is a substrate connection portion, and Ls is a wiring (a wiring that directly connects the emitter connection portion E and the ground line G). As shown, signal line 1. ,,L
2 is detoured and arranged between the base electrode part and the emitter electrode part of the bipolar transistor T, and the wiring 1.2 is directly connected between the emitter electrode part and the ground line G. s is now possible.

This becomes clear when comparing the plan view shown in FIG. 1 with the circuit diagram shown in FIG. The parasitic resistance rl shown in is almost zero. On the other hand, since the base electrode part B is connected to the ground line G through the inside of the long board via the board connection parts S3 and 54, the parasitic resistance r
2 occurs. However, the presence of the parasitic resistance r2 does not cause much harm, and the structure of the protection element according to the present invention in which the parasitic resistance r1 is removed completely absorbs external overvoltage and provides sufficient protection from electrostatic damage. Can be done. Therefore, I
The reliability of C can be further improved.

Note that although the above embodiment has been described using the lowest potential line as the ground line, a circuit having a lowest potential line (for example, a power supply line) that is lower in potential than the ground line may also have the lowest potential line and the emitter electrode section. It goes without saying that the present invention can be applied by a method of connecting by direct wiring, and can also be applied to single-layer wiring mask slice ICs other than analog ones.

[Effects of the Invention] As is clear from the description of the embodiments above, if the electrostatic protection element according to the present invention is provided, the reliability of the mask slice IC can be further improved.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the protection element portion according to the present invention, FIG. 2 is a DD sectional view of FIG. 1, FIG. 3 is a circuit diagram of the protection element, and FIG. 4 is a plan view of the conventional protection element portion. FIG. 5 is a sectional view along line AA in FIG. 4. In the figure, T is a transistor (bipolar transistor), rl,
r2 is the parasitic resistance, C is the collector electrode, B is the base electrode, E is the emitter electrode, G is the ground line (lowest potential line), L, L2 is the signal line, and Pa is the bonding path (external input terminal). ), S,, S2
is the substrate connection part, Lo is the wiring, Ls is the wiring (the wiring that directly connects the emitter connection part E and the ground line G), 1 is the P-type silicon substrate, 2 is the N-type collector region, 3 is the P-type base region, 4 indicates an N+ type emitter region. 1st A To 1st hearing DDur life chart 2nd diagram allll) l1lOnQ 3rd diagram I voice? j toy j mi gl self 1 [city 7 poor de 1ri plane rn]
Figure 4? 41ZI tQAA @ffxr mFigure 5

Claims (1)

[Claims] In a semiconductor integrated circuit using a single-layer wiring master slice method, a signal line is provided between a base electrode and an emitter electrode of a protection element made of a bipolar transistor, and the emitter electrode and the lowest potential line are directly connected by wiring. An electrostatic protection element characterized by: