BACKGROUND

The present invention relates to a semiconductor device, display device and electronic apparatus, and more particularly, to a display device having a driving circuit provided on an active matrix substrate.

In a semiconductor device, it is important to take measure against the electro-static damages (ESD) when a high voltage caused by a static electricity or a various noise phenomenon is unintentionally applied to the inside of the device to damage an insulating film, thereby causing a fatal damage to the device. In order to prevent the problem, various protective circuits have been proposed. For example, in Patent Documents 1 and 2, it has been proposed that an abnormal voltage applied to lines is discharged to GND, etc. by proper combination of diodes. However, since general semiconductor devices are formed on a silicon wafer made of conductive material, there are little chances of being electrified within the semiconductor device, so that it is a key issue to prevent the damage when a static electricity flows through input terminals. To solve such a problem, conventionally, protective circuits are formed between input terminals and the semiconductor device forming a circuit, i.e., immediately after the input terminals, so that it is prevented that the high voltage from the input terminals is transmitted to the device.

On the other hand, in a display device using an active element such as a thin film transistor (TFT), which has been rapidly spread in recent years, a device is formed on an insulating substrate. As a result, there is a problem in that it is easy that the device is easily electrified by static electricity, and that the electro-static damage is generated during the manufacturing process. On this account, for example, an electro-static measure is taken by forming an antistatic line, called as a guide ring or a short ring, at the periphery of an active matrix circuit.

In recent years, a display device having a built-in driving circuit has been widely spread, in which an improvement of a definition, a cost reduction and better reliability are realized by using a polysilicon TFT having polysilicon serving as an active layer. In such a device, as a measure against the static electricity of the driving circuit, a conventional method used in a semiconductor on a silicon wafer is applied as it is, so that only protective circuits for preventing the static electricity from the input terminals are built in, and a conventional method of a display device not having the built-in driving circuit is used to protect the active matrix circuit from the static electricity. Hereinafter, the conventional art relating to the protection of the driving circuit will be described in detail with respect toFIG. 11.

FIG. 11is a view illustrating a configuration of an active matrix substrate of a VGA-LCD using polysilicon TFT by the conventional art. Reference numerals201-1to201-480indicate scanning lines of the active matrix circuit, driven by a scanning line driving circuit800. Reference numerals202-1to202-1920indicate data lines, and pixel transistors401composed of n-type transistors and pixel electrodes402are formed at intersections of the scanning lines and the data lines, respectively, to drive a liquid crystal device.

Reference numerals801-1to801-480indicate scanning line driving unit circuits composed of 480 stages, which form the scanning line driving circuit800, and each of them is composed by a CMOS circuit. A specific configuration of the scanning line driving unit circuits801-1to801-nis shown inFIG. 5.

Each of the scanning line driving unit circuits801-1to801-480is connected to a low potential power line750and a high potential power line751, through which power is supplied. The low potential power line750is connected to a low potential power terminal650, the high potential power line751is connected to a high potential power terminal651. Also, the low potential power terminal650and the high potential power terminal651are connected to a power IC through a FPC, and they are supplied with reference potentials of a potential VS and a potential VD, respectively. Herein, VS is less than VD.

Further, a signal (for example, a clock signal) required for the operation of each of the scanning line driving unit circuits801-1to801-480are supplied from an external IC through signal lines701and702and signal terminals601and602.

Here, in order to prevent TFTs constituting each of the scanning line driving unit circuits801-1to801-480from being damaged by the static electricity or noise current input through the low potential power terminal650, the high potential power terminal651and the signal terminals601and602, static electricity protection circuits ESD1to ESD4are provided between the input terminals601,650and651and the scanning line driving unit circuits801-1to801-480, respectively. A specific configuration of the static electricity protection circuit ESD1to ESD4is shown in Patent Document 1 and Patent Document 2.[Patent Document 1] Japanese Patent No. 2884946[Patent Document 2] Japanese Patent No. 3141511

However, in the driving circuit on an insulating substrate, it is difficult for charges to escape as compared to the circuit on silicon wafer, and it is easy to be electrified. In addition, in the case that the driving circuit of the display device is formed on a glass substrate, the area of the circuit is larger as compared to the IC formed on a general silicon wafer. Therefore, in such a configuration, there is a problem in that a protection of the wiring lines far from the input terminals against the static electricity is not sufficient, especially during a manufacturing process. Specifically, since there is a possibility that the static electricity is electrified on a certain location on the substrate during the manufacturing process, when the distance from the electrified location to the static electricity protection circuit is long and the line resistance is high, a transistor within a circuit located closer than the static electricity protection circuit is damaged by the static electricity even before the static electricity protection circuit starts the operation. Such a problem is the same in a semiconductor device using a SOT substrate.

Further, in a case of an insulating substrate, a large current may flow in the wiring lines by electrostatic induction when strong electrostatic discharge occurs in the outside of the substrate even in a finished product state after completion of the manufacturing process. Even in such a case, there is a possibility that a circuit located far from the terminal is damaged.

Furthermore, the present invention provides a measure against the problem in that potentials on the wiring lines are instantaneously changed, when a large amount of current flows in the wiring lines through a circuit.

SUMMARY

In order to solve the above problems, it is proposed that a semiconductor circuit be disposed between protective circuits and input terminals. More specifically, it is proposed that an electrical resistance between a connection part connecting the semiconductor circuit to wiring lines and input terminals be lower than an electrical resistance between a connection part connecting the protective circuits to the wiring lines and the input terminals.

Thus, there is an effect that the protection against the static electricity is sufficiently obtained even in a place far from the terminal, by providing internal protective circuits in an area which is not connected to the input terminals of the wiring lines as well as providing the protective circuits around the input terminals as in the conventional art.

Further, it is proposed that a plurality of the protective circuits are arranged on the wiring lines and the semiconductor circuit is interposed between the protective circuits. Thereby, it is possible to prevent the static electricity or noise input from the input terminals, and to protect a semiconductor circuit far from the input terminals. In addition, it is preferable that the plurality of the protective circuits be arranged with a predetermined gap therebetween, thereby the entire part of the semiconductor circuit connected to the wiring lines can be protected.

Furthermore, in the present invention, it is proposed that the wiring line include a low potential power line and a high potential power line, and the protective circuits between power sources connected to both of the low potential power line and the high potential power line is comprised. In this configuration, the protective circuit can be easily formed by a diode element, etc., and since all are power lines, it is difficult to be affected by the noise. Also, in general, the power line is remarkably lengthened within a circuit, so that it requires a static protection more than other lines. Therefore, the effect is remarkable. In addition to this, for a signal line, it is proposed that the protective circuits between signal power sources be formed between the power lines. Since it is easy to be affected by the noise between the signal lines, it is possible to reduce an adverse influence by providing the protective circuit between the power source and the signal line. Also, it is proposed that the capacitance of the protective circuits between signal power sources be lower than the capacitance of the protective circuits between the power sources. In this way, it is possible to minimize an influence on the power line by the signal.

Further, in the present invention, the capacitive component between the wiring lines in the protective circuits is not less than I×t×0.1 (F) when the maximum current flowing in the low potential power line or the high potential power line is I (A) and the maximum tolerable time when a voltage drop in power line occurs is t (second). t is preferably below 10−8(second) in consideration of general operation time in a polysilicon TFT. Thereby, when a large amount of current flows in the circuit and a supply from the outside is not sufficient to follow it to generate instantaneous voltage changes on the wiring lines, there is an effect that the voltage changes are reduced by the capacitive components within the protective circuits.

Further, in the present invention, it is proposed that the protective circuit between power sources or the protective circuit between signal power sources include a diode element, and one end of the diode element is connected to the power line. In this configuration, the static electricity or the noise current is easily discharged, so that the protective performance is remarkably improved.

Further, in the present invention, it is proposed that contents of the invention described above is applied to a so-called CMOS type semiconductor device, which is composed of an n-channel type field effect transistor and a p-channel type field effect transistor. Because the CMOS type semiconductor device requires at least 2 types of reference power source, the number of power line is increased, so that the effect of this invention is remarkable. Particularly, in the CMOS type semiconductor device composed of the polysilicon thin film transistor, the substrate is an insulating substrate, and thus electrification easily occurs under a state in which there is no protective circuit, so that the effect of the present invention is more prominent. Further, when an active matrix used in a TFT-LCD or TFT-OLED and a driving circuit thereof are formed on the insulating substrate, the driving circuit is configured to surround the active matrix, so that it becomes larger and accordingly its line is also lengthened. As a result, the effect of the present invention is more remarkable.

Further, in the present invention, it is proposed that, when the active matrix is applied to the present invention, internal protective circuits are arranged at corners far from the input terminals among four corners of the active matrix. By such a configuration, it is possible to arrange large-sized protective circuits without making the peripheral area large.

Moreover, in a display device using the semiconductor device of the present invention and an electronic apparatus having the display device, the electro-static damage is difficult to be generated during a manufacturing process, so that it is advantageous in terms of cost, and it is difficult that the voltage drop at the power source occurs, so that there is an effect that the display quality is improved.

