CN100454553C - Thin film semiconductor device and method of manufacturing the same, electro-optical device, and electronic apparatus - Google Patents

Abstract

In a thin film semiconductor device including a base and a semiconductor film formed on the base, an internal circuit (main circuit portion) (17), a protection circuit portion (18), and a terminal portion (19) are provided on the base. On the protection circuit part (18), there are protection circuit elements (181, 182), which have a PIN diode of the semiconductor film, and a floating diode arranged oppositely between the I layer and the insulating film of the PIN diode. electrode. It is possible to provide a thin-film semiconductor device capable of constituting a protection circuit that can well protect internal circuits from surge voltages, and that does not cause failure in the circuit structure when it is destroyed by excessive voltage, and that has excellent reliability as a circuit element .

Description

Thin film semiconductor device and manufacturing method thereof, electro-optical device, electronic device

technical field

The present invention relates to a thin film semiconductor device, a manufacturing method thereof, an electro-optical device, and an electronic device.

Background technique

Conventionally, semiconductor integrated circuit devices and active matrix electro-optical devices are provided with protection circuits for protecting internal circuits from static electricity. For example, in an electro-optical device, a protection circuit is provided between internal circuits such as a pixel switching element and a drive circuit, and pads for extraction electrodes. A diode is used as a protection circuit in a semiconductor integrated circuit device, and a thin film transistor (TFT) connected to a diode is used in an electro-optical device. The reason is that it is difficult to form a TFT using a thin film semiconductor layer formed on an insulating plate and a PN junction of a diode on the thin film semiconductor layer in an electro-optical device (for example, refer to Patent Document 1).

Patent document: Japanese Patent Application Laid-Open No. 6-51346.

9( a ) is a circuit configuration diagram showing a protection circuit using a diode-connected TFT, and ( b ) is a schematic cross-sectional view of the same diode-connected TFT. As shown in FIG. 9( a), two resistance elements R1, R2 are inserted between the connection pad 219 and the internal circuit 217, and in the middle of these resistance elements R1 and R2, the connection pads 219b (Vdd) and 219c ( Vss) connected to the line, respectively insert a diode connected to TFT30D. Referring to the cross-sectional structure shown in FIG. 9( b ), the diode connection TFT 30D includes: a semiconductor film 201 formed on a substrate 211 , and a gate electrode 213 a opposite to the gate insulating film 212 of the semiconductor film 201 ; The inside of the connection hole of the insulating films 212 and 216 is connected to the source electrode 208 and the drain electrode 209 of the semiconductor film 201 . Therefore, the connection electrode 213d connected to the gate 213a through the connection hole provided through the insulating film 216 and the drain electrode 209 are short-circuited to form a diode-connected TFT.

With such a structure, when a positive surge voltage is input from the connection pad 219a, a current i flows through the diode connection TFT 30D, and an excessive current flow into the internal circuit 217 cannot be prevented.

In the protection circuit configured as above, if TFTs are connected with diodes in the protection circuit, there is an advantage that the protection circuit can be formed by utilizing the steps of TFTs constituting the internal circuit. However, in such a structure, as shown in FIG. 9(b), if a surge voltage exceeding the withstand voltage of the diode connection TFT 30D is introduced, the diode connection TFT 30D will be charged through the gate insulating film 212 which is a thin insulating film. And a short-circuit line bd is formed. When such a short-circuit state is formed, conduction is conducted from the source region 201b of the semiconductor film 201 through the short-circuit line bd and the gate electrode 213a. As a result, the drain electrode 209 and the source electrode 208 connected to the gate electrode 213a are turned on. Then, the connection pad 219 shown in FIG. 9( a ) becomes conductive with other connection pads 219b to 219c, and the connection pad 219a does not function normally, and the semiconductor device itself malfunctions.

Contents of the invention

The present invention is made in view of the above-mentioned problems of the prior art, and an object thereof is to provide a thin film semiconductor device having a protection circuit capable of well protecting an internal circuit from a surge voltage, and a method of manufacturing the same. A circuit element with excellent reliability that will not cause failure in the circuit structure when it is destroyed by excessive voltage.

In order to solve the above problems, the present invention provides a thin film semiconductor device, which includes a substrate and a semiconductor film formed on the substrate, and is characterized in that a main circuit part having a semiconductor element is provided on the substrate, and the main circuit part extends from the main circuit part. The terminal portion of the main circuit portion and the protection circuit portion inserted between the main circuit portion and the terminal portion, the protection circuit portion is provided with a protection circuit element, the protection circuit element includes: a PIN diode having the semiconductor film, and a The insulating film and the floating electrode arranged opposite to the I layer of the diode.

The PIN diode is a diode having a semiconductor film divided into a well-known P layer (P-type semiconductor layer), I layer (semiconductor layer into which impurities are intrinsically or at a slight concentration) and N layer (N-type semiconductor layer). In addition, the floating electrode is an electrode in an electrically "floating" state without being connected to other electrically controlled conductive films or constituent members of the semiconductor layer.

Since the protection circuit element included in the thin film semiconductor device of the present invention includes a PIN diode and a floating electrode disposed opposite to its I layer, if an excessive current flows through the protection circuit element, the gate insulating film is destroyed and the electric current is damaged. In the case of penetration, the P layer (or N layer) and the floating electrode of the PIN diode form a short-circuit structure. However, since the floating electrode is not connected to other electrically controlled conductive layers or semiconductor layers, the insulation of the PIN diode can be ensured even after the protection circuit element is destroyed. Therefore, if a protection circuit is constructed using the above-mentioned protection circuit elements, a thin film semiconductor device can be provided that can constitute an electrostatic protection circuit that can well bypass surge voltage caused by static electricity, and input a surge sufficient to destroy the protection circuit elements. It can still work after voltage.

In addition, there is a large difference in protection performance in the reverse direction between the case where the above-mentioned floating electrode is provided and the case where the above-mentioned floating electrode is not provided. Such a good semiconductor layer does not have a state of floating electrodes, and cannot have protection performance even against a voltage corresponding to the breakdown voltage, and a slight current leakage occurs by providing floating electrodes. It is possible to have a protection function even against the reverse surge voltage which is caused by this even slightly and which negatively affects the TFT device.

The protection circuit element can ensure the insulation of the main body even if it is broken due to excessive current flow. For this reason, if a protective circuit unit including such a protective circuit element is provided, even if an excessive surge current is introduced from the terminal portion, and the protective circuit element is destroyed due to the current, it is different from the conventional protective circuit element composed of a diode-connected TFT. Differently, the circuit structure of the connection terminal part and the main circuit part does not change. Therefore, according to the present invention, it is possible to provide a thin film semiconductor device capable of normal operation even after a surge voltage sufficient to destroy a protection circuit element is introduced, and has high reliability and long life.

In the thin film semiconductor device according to the present invention, it is preferable that the semiconductor film constituting the PIN diode and the semiconductor film constituting the semiconductor element of the main circuit portion are formed in the same layer on the base. With such a structure, since the semiconductor element and the PIN diode of the main circuit portion can be formed in the same process, the reliability of the thin film semiconductor device can be improved without being affected by changes in the manufacturing process.

In the thin film semiconductor device of the present invention, the semiconductor element provided in the main circuit part is a thin film transistor, and the conductive film constituting the floating electrode and the conductive film constituting the gate electrode of the thin film transistor are preferably made of into a structure formed in the same layer on the substrate. With this structure, there is an advantage that the thin film transistors of the main circuit portion and the protection circuit elements can be formed in the same process.

In the thin-film semiconductor device of the present invention, it is preferable that the floating electrode and the I layer of the PIN diode are formed at substantially the same position in plan view. With this structure, since the I layer of the PIN transistor can be self-matched by introducing impurities into the semiconductor film using the floating electrode as a mask mask, it becomes a protection circuit element that can be manufactured with a simple process. In the related structure, if a thin film transistor is provided in the main circuit part, since the gate of the thin film transistor is used as a mask mask, the process of forming the channel region by self-matching can be simultaneously formed. I layer, and thus can become a thin film semiconductor device with better manufacturing efficiency.

In the thin film semiconductor device of the present invention, the PIN diode may have a low-concentration impurity region between the P layer and the I layer or between the N layer and the I layer, which is lower in impurity concentration than the P layer or the N layer. structure. Like ordinary semiconductor devices, in thin film transistors provided in thin film semiconductor devices, in order to prevent the deterioration of electrical characteristics caused by hot carriers, LDD (Lightly Doped Drain) structure is often used. Therefore, if the PIN diode related to this structure is used, it is possible to effectively seek generalization of the manufacturing process for the case where the protective circuit element is formed at the same time as the thin film transistor having the LDD structure. The invention can provide a protective circuit element with better electrical characteristics, which can further improve the withstand voltage of the PIN diode and has high reliability.

In the thin film semiconductor device of the present invention, the low-concentration impurity region may be a structure formed in a region overlapping with the plane of the floating electrode. With such a structure, the thin-film transistor in the main circuit part is a device with a GOLDD (Gate Overlapped Lightly Doped Drain) structure, and the manufacturing process can be shared, and the withstand voltage of the PIN diode can be further improved.

In the thin film semiconductor device of the present invention, the floating electrode disposed opposite to the I layer of the PIN diode between the insulating film and the PIN diode may have a part that overlaps with a part of the P layer or the N layer of the PIN diode on the plane. structure.

Such a structure is not necessarily limited to the method of forming a channel region by so-called self-matching by using a floating electrode arranged to overlap a part of the semiconductor film on a plane as a mask to introduce impurities into the semiconductor film. Therefore, it is also possible to introduce impurities into the semiconductor film using a photoresist patterned on an ordinary insulating film as a mask, and in such a case, the degree of freedom in the manufacturing process can be increased. That is, the main circuit and the protection circuit element may be manufactured in a common manufacturing process, or may be manufactured in another process. Even if the manufacturing process corresponding to this situation is different, the electrical characteristics of the obtained protective circuit element can be reproduced as described above, but it cannot be said that there is no change.

In the thin film semiconductor device of the present invention, it is preferable that the protection circuit element is directly connected to the terminal portion.

As shown in FIG. 9, in a protection circuit using a conventional diode connection TFT as a protection circuit element, a resistance element R1 is provided between the connection pad 219a and the diode connection TFT 30D. The resistive element R1 is an element formed of a normal N-type or P-type semiconductor layer, functions to suppress a sudden voltage rise caused by a surge introduced from the connection pad 219a, and protects the diode-connected TFT 30D. Even if the diode connection TFT 30D is broken and turned on, it serves to avoid direct short-circuiting between the power supply line Vdd or Vss and the connection pad 219a. On the contrary, in the thin film semiconductor device according to the present invention, even if the protection circuit element as described above is destroyed, since the pad 219a is not directly short-circuited with the power line Vdd or Vss, the connection between the terminal portion and the main short-circuit portion can be ensured. conduction. But on the contrary, if a resistance element is inserted between the protection circuit element and the terminal part, the resistance element will be destroyed when the input surge voltage is too large, and the thin film semiconductor device will be damaged due to a disconnection between the terminal part and the internal circuit part. become non-functional. Therefore, by directly connecting the protective circuit element and the terminal portion as in this configuration, it becomes a thin film semiconductor device that ensures normal operation of the main circuit portion even if a voltage sufficient to destroy the element of the protective circuit portion is introduced.

The method for manufacturing a thin film semiconductor device of the present invention is a method for manufacturing a thin film semiconductor device having a substrate and a semiconductor film formed on the substrate, wherein the thin film semiconductor device is provided with a main circuit portion having a semiconductor element on the substrate. , a terminal part extending from the main circuit part, a protection circuit part inserted into the main circuit part and the terminal part, the process of forming the protection circuit part includes a protection circuit element forming process, and the protection circuit element forming process includes: A step of forming a semiconductor film on a substrate, a step of forming an insulating film on the semiconductor film, a step of forming a floating electrode planarly overlapping the semiconductor film by patterning a conductive film on the insulating film, A step of introducing impurities into the semiconductor film by using the floating electrode as a mask to form a PIN diode on which a P layer, an N layer, and an I layer are formed. With this manufacturing method, since the layers of the PIN diode are formed by introducing impurities into the semiconductor film using the floating electrode as a mask, it is possible to form a protective circuit element with high efficiency and excellent reliability, and it is possible to easily and efficiently manufacture high Reliable thin film semiconductor devices.

According to this manufacturing method, it is possible to easily and efficiently manufacture a thin-film semiconductor device having externally connected electrons and a thin-film semiconductor device capable of well protecting the main circuit part from surge voltage introduced from the terminal part.

The method for manufacturing a thin film semiconductor device according to the present invention can be such that the main circuit part includes a thin film transistor including a semiconductor film and a gate electrode facing the semiconductor film with an insulating film interposed therebetween, and the thin film transistor is constituted. The semiconductor film and the semiconductor film constituting the protection circuit element are formed in the same process, and the gate electrode constituting the thin film transistor and the floating electrode constituting the protection circuit element are formed in the same process. In addition, in the manufacturing method of the thin film semiconductor device of the present invention, it is preferable that the source or drain of the thin film transistor and the P layer or N layer of the PIN diode are formed by the same impurity introducing step.

According to this manufacturing method, the thin film transistors and protective circuit elements constituting the main circuit portion can be manufactured in the same process, and a highly reliable and excellent thin film semiconductor device that is not affected by changes in the conventional manufacturing process can be manufactured.

In the method for manufacturing a thin film semiconductor device according to the present invention, in the impurity introducing step, the semiconductor film of the thin film transistor and the semiconductor film of the protective circuit element can be formed at a low impurity concentration lower than that of the adjacent impurity introduction region. Impurities field. According to the related manufacturing method, a thin film transistor having an LDD structure and a protection circuit element having a structure having a withstand voltage higher than that of the PIN diode can be formed in the same process.

The electro-optical device of the present invention is characterized by including the aforementioned thin-film semiconductor device. The thin-film semiconductor device according to the previous invention can be used as a TFT array substrate of an active matrix electro-optical device. In the related TFT array substrate, TFTs are used as switching elements constituting pixels in the image display area, and inverters using TFTs are also formed in the drive circuits provided in the edge area. In addition, a terminal portion serving as an external connection terminal is also provided. Therefore, if the structure of the present invention is applied to the related TFT array substrate, the switching element and the driving circuit in the above-mentioned image display area constituting the internal circuit can be well protected by the protection circuit section, and an electro-optical device with excellent reliability and long life can be constructed.

Next, the electronic device of the present invention is characterized by having the electro-optical device of the present invention described above. With this configuration, it is possible to provide an electronic device having a protection circuit capable of well protecting the internal circuit from excessive voltage such as a surge voltage, and a display unit having excellent reliability and a long life.

Description of drawings

FIG. 1 is a configuration diagram of a protection circuit of a thin film semiconductor device according to the first embodiment of the present invention.

2 is a plan view and a cross-sectional view of a protective circuit element according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a liquid crystal display device according to an embodiment of the present invention.

4 is a circuit structure diagram of a liquid crystal display device of the present invention and a cross-sectional view of a thin film transistor (TFT).

5 is a schematic cross-sectional view of a protection circuit element according to a second embodiment of the present invention.

6 is a schematic cross-sectional view of a protection circuit element according to a third embodiment of the present invention.

7 is a schematic cross-sectional view of a protection circuit element according to a fourth embodiment of the present invention.

FIG. 8 is a perspective view showing an example of an electronic device.

FIG. 9 is a diagram showing a protection circuit of a conventional thin film semiconductor device.

FIG. 10 is a graph comparing the TLP characteristics of PIN diodes with and without the floating electrodes according to the present invention.

FIG. 11 is a structural diagram of protection circuits of other thin film semiconductor devices related to the present invention.

Fig. 12 is a graph comparing the electrical characteristics of PIN diodes with and without the low-concentration region related to the present invention.

In the figure: 11-substrate (base body), 2-first insulating film (gate insulating film), 6-second insulating film (interlayer insulating film), 181a-PIN diode, 118p-p layer, 118n-N layer , 118i-I layer, 118s-semiconductor film, 118g-floating electrode, 181, 182, 281, 381, 481-protection circuit elements (thin film semiconductor elements), 218n, 318n-low-concentration impurity regions.

Detailed ways

[first embodiment]

Embodiments of the present invention will be described below with reference to the drawings. This embodiment mode exemplifies the basic structure of the thin-film semiconductor device according to the present invention and an electro-optical element in which the thin-film semiconductor device is mounted.

(thin film semiconductor device)

FIG. 1 is a schematic configuration diagram showing a circuit configuration of a thin film semiconductor device according to the present invention. As shown in FIG. 1 , the thin film semiconductor device of this embodiment includes an internal circuit (main circuit portion) 17 , a protection circuit portion 18 , and a terminal portion 19 . A plurality of connection pads 19 a to 19 c are provided on the terminal portion 19 . A protection circuit unit 18 is interposed between these connection pads 19 a to 19 c and the internal circuit 17 . The connection pads 19b, 9c are power input terminals (Vdd, Vss).

The protection circuit unit 18 includes a plurality of protection circuit elements 181 and 182 connected in series. The signal wiring 23 extending from the connection pad 19a is connected between the two protection circuit elements 181, 182 through the resistance element 18b. On the other hand, the signal wiring 24 extending from the internal circuit 17 is connected to the protection circuit elements 181 and 182 and the signal wiring 23 through the resistance element 18c.

In addition, one end (cathode side) of the protection circuit element 181 is connected to the connection pad 19b (Vdd) which is a power supply input terminal through a signal wiring. One end (anode side) of the protection circuit element 182 is connected to the connection pad 19c (Vss) through a signal wiring.

FIG. 2(a) is a plan view showing a specific structural example of 181 shown in FIG. 1, and FIG. 2(b) is a cross-sectional view along line A-A of FIG. 2(a).

In addition, in FIG. 2, only the main part of the protection circuit part 181 is shown, and the wiring etc. connected to the same element are omitted. In addition, the other protection circuit element 182 also has the same structure as the protection circuit element 181 .

As shown in FIG. 2 , the protection circuit element 181 according to this embodiment includes a PIN diode 181 a and a floating electrode 118 g arranged to overlap a part of the PIN diode 181 a planarly. The PIN diode 181a includes a semiconductor film 118s, and a plurality of (four shown in the drawing) anode electrodes 118a and a plurality of (four shown in the drawing) cathode electrodes 118c connected to the semiconductor film 118s. On the semiconductor film 118s, a P layer 118p, an N layer 118n, and an I layer 118i disposed therebetween are formed, the anode electrode 118a is electrically connected to the P layer 118p, and the cathode electrode 118c is electrically connected to the N layer 118n. Furthermore, the floating electrode 118g is disposed opposite to the I layer 118i of the PIN diode 181a.

Referring to the cross-sectional structure of FIG. 2(b), a semiconductor film 118s such as polysilicon film is formed on the substrate 11, and a first insulating film 2 such as silicon oxide is formed covering the semiconductor film 118s. A floating electrode 118g made of, for example, aluminum, tantalum, molybdenum, polysilicon, etc. is formed on the first insulating film 2, and a second insulating film 6 covering the floating electrode 118g is formed. Therefore, the anode electrode 118a and the cathode electrode 118c are embedded in the connection hole reaching the semiconductor film 118s penetrating the second insulating film 6 and the first insulating film 2, and are electrically connected to the P layer 118p and the N layer 118n, respectively.

The floating electrode 118g included in the protection circuit element 181 is formed of a conductive film buried between the first insulating film 2 and the second insulating film 6 as shown in FIG. An electrode of any potential is obtained without being grounded.

In addition, the internal circuit 17 shown in FIG. 1, like the protection circuit unit 18, includes a semiconductor element formed of a thin film semiconductor film formed on a substrate, and has a structure such as a TFT (Thin Film Transistor).

According to the thin film semiconductor device of this embodiment having the above-mentioned structure, the internal circuit 17 can be well protected from positive surge voltage such as static electricity introduced through the pad 19a by the protection circuit portion 18 provided with the protection circuit element 181. Influence. That is, when a surge voltage is introduced from the connection pad 19a, a current flows between the PIN diodes 181 and 182, and the surge current is bypassed to the power input terminal side, preventing excessive current from flowing to the internal circuit 17 side.

In addition, in the thin film semiconductor device of this embodiment, even when the protection circuit elements 181 and 182 are destroyed by a surge voltage exceeding the breakdown voltage, the electrical connection between the internal circuit 17 and the connection pad 19a does not malfunction. This is an advantage that could not be obtained in the protection circuit of conventional diode-connected TFTs.

If the protection circuit element 181 shown in FIG. 2 is used to describe specifically, for the case where the protection circuit element 181 having the floating electrode 118g is destroyed, like the diode connection electrode TFT 30D shown in FIG. The first insulating film 2 is degraded by the through charge, and the P layer 118p (or N layer 118n) of the PIN diode 181a and the floating electrode 118g are often short-circuited. In addition, in this short-circuit state, corresponding to the conduction state of the conventional diode-connected TFT 30D, in the protection circuit element 118 according to the present embodiment, the short circuit between the P layer 118p and the floating electrode 118g is formed, and since the floating electrode There is no electrical connection between 118g and other structural devices, and there is no short circuit between the anode electrode 118a and the cathode electrode 118c of the PIN diode 181a. Therefore, the destroyed protective circuit element 181 functions as a simple insulator. Therefore, by maintaining the circuit connection between the pad 19a and the internal circuit 19, even if a surge voltage exceeding the withstand voltage of the protection circuit is introduced, the thin film semiconductor device can operate normally without failure.

In addition, the protection circuit element of the present embodiment produces the same effect even against a surge voltage in the opposite direction. Figure 10 shows the TLP (transmission line pulse) measurement results of PIN diodes with and without floating electrodes. The horizontal axis represents the load voltage of the protection circuit element in the opposite direction. The vertical axis represents the current flowing through the protection circuit element at this time. In addition, the solid line in the figure is the case where there is a floating electrode, and the dotted line is the case where there is no floating electrode. As can be seen from this figure, the slope of the curve of the diode having a floating electrode becomes larger in a region where the load voltage exceeds 20V. In other words, the present embodiment has current characteristics in the low load voltage region even for voltages in opposite directions. Therefore, with the protection element of this embodiment, it is possible to constitute a protection circuit that bypasses low surge voltage regardless of whether it is in the forward direction or in the reverse direction. According to the present invention, the protection performance of the bipolar protection element can be exhibited.

In addition, the thin film semiconductor device having the protective circuit portion 18 that can achieve the above-mentioned effects, as shown in FIG. 11, may also be configured without the resistor element 18b shown in FIG. A structure in which pads 19a are directly connected by wires 23 . The resistance element 18b, when the surge voltage is introduced from the pad 19a, suppresses the sharp rise of the voltage in the circuit, and plays a role in protecting the circuit. For the situation of introducing an excessive surge voltage, even the resistance element 18b is also destroyed, sometimes A disconnection occurs. Therefore, if such a resistance element 18b is disconnected, the connection pad 19a and the internal circuit 17 are disconnected, which causes trouble in the operation of the thin film semiconductor. In this regard, if the protection circuit elements 181, 182 are provided without the structure of the resistance element 18b, even if the protection circuit elements are damaged due to the introduction of excessive surge voltage, due to the connection between the pad 19a and the internal Since the electric circuit 17 ensures continuity, the thin-film semiconductor device itself does not fail to operate due to damage to the protection circuit unit 18, and the lifetime of the thin-film semiconductor device can be extended.

(electro-optical device)

In the semiconductor device according to the present invention described above, an active-matrix-type device can be configured. Hereinafter, an active matrix transmissive liquid crystal display device will be described as an example of an electro-optical device including the thin film semiconductor device shown in FIG. 1 .

Fig. 3(a) is a plan view illustrating the liquid crystal display device of this embodiment viewed from the side of each component and the opposing substrate, and Fig. 3(b) is a cross-sectional view along line H-H' of Fig. 3(a). In addition, in each drawing used for the following description, each layer and each device have a different scale so that each layer and each device have a size recognizable on the drawing.

The liquid crystal display device 10 of this embodiment, as shown in Figure 3 (a), (b), has a TFT array substrate 11 (substrate) formed by a transparent substrate and a counter substrate 12 bonded by a sealing material 13. The liquid crystal layer 14 is enclosed in the space divided by the material 13 . An image display region 17 c is formed in a substantially central portion of the TFT array substrate 11 . In the outer edge region 16, a data line driving circuit 17a is provided along one long side region of the TFT array substrate 11 (the side along the X direction in FIG. 3). The data line driving circuit 17a is composed of the same number of unit circuits (not shown) as the number of pixels in the X direction of the image display area 17c. On the other hand, on both sides of the image display area 17c, two scan line drive circuits 17b are provided along the two short sides of the TFT array substrate 11 (the sides along the Y direction in FIG. 3 ). Furthermore, a plurality of wires 22 are provided on the remaining side of the TFT array substrate 11 to connect the scanning line driving circuits 17b and 17b provided on both sides of the image display area 17c.

In addition, a plurality of connection pads 19a for connecting FPCs on the TFT array substrate 11 are arranged in a row at a predetermined pitch along the X direction near the edge end of the data line driving circuit 17a of the TFT array substrate 11 . Therefore, a protection circuit unit 18 is provided between these connection pads 19a and the data line drive circuit 17a. The plurality of wires 23 and 24 extending from the connection pad 19a are electrically connected to the data line drive circuit 17a, the scan line drive circuits 17b and 17b, and the connection pad 19a through the protection circuit unit 18.

Therefore, in the liquid crystal display device 10 of the present embodiment, the data line driving circuit 17a, the two scanning line driving circuits 17b, and the image display area 17c correspond to components of the internal circuit (main circuit unit) 17 shown in FIG. 1 . This internal circuit is electrically connected to the connection portion 19 having a plurality of connection pads 19 a through the protection circuit portion 18 .

In addition, as shown in FIG. 1 and FIG. 2, the protection circuit part 18 provided between the data line drive circuit 17a and the connection pads 19a... is an electrostatic protection circuit mainly formed of protection circuit elements 181 and 182. By protecting the circuit elements 181, 182 bypass the surge current to protect the pixel switching elements and the driving circuits 17a, 17b formed in the image display region 17c. In addition, in the present embodiment, two protective circuit units 18 are provided in the image display area for the left side and for the right side of the image display area 17c.

In addition, an inter-substrate conduction material 25 (upper and lower conduction portions) for conduction between the TFT array substrate 11 and the opposite substrate 12 is arranged at the corner of the opposite substrate 12 . A common electrode (not shown) is provided on the counter substrate 12 . The wiring 32 for supplying a common potential to the common electrode is provided on the TFT array substrate 11 through the inter-substrate conductive material 25 and arranged at the outermost peripheral position of the TFT array substrate 11 . Component elements shown with reference numeral 9 in FIG. 3( b ) are pixel electrodes provided for each pixel in the image display region 17 c.

Next, FIG. 4( a ) is a circuit configuration diagram of the liquid crystal display device 10 . Drawing (b) is a figure which shows the schematic cross-sectional structure of TFT30 shown in drawing (a). As shown in Figure 4 (a), a plurality of data lines 6a and scan lines 3a extending across each other are formed on the image display area 17c of the liquid crystal display device 10, in a rectangular shape surrounded by the data lines 6a and the scan lines 3a Pixels X are provided in the region, and only one pixel is shown in FIG. 4 . In the pixel display region 17c, a plurality of pixels X are arranged in a matrix in plan view.

In each pixel X, corresponding to the position where the data line 6a and the scanning line 3a intersect, a TFT 30 as a pixel switching element is arranged, the scanning line 3a is connected to the gate of the TFT 30, the data line 6a is connected to the source, and the drain is connected to the The liquid crystal layer 14 applies an electric field to the pixel electrode 9 . Also, a storage capacitor 70 is connected in parallel with the pixel electrode 9, and an electrode opposite to the pixel electrode 9 is connected to the capacitance line 3b.

If only referring to the cross-sectional structure of TFT 30 shown in FIG. The gate electrode (scanning line) 3a facing the insulating film 2 and the semiconductor film 1a. The semiconductor film 1a has a source region 1b, a drain region 1c, and a channel region 1a'. In the semiconductor film 1a, the channel region 1a' faces the gate electrode 3a. An interlayer insulating film (second insulating film) 6 covering the gate electrode 3a and the gate insulating film 2 is formed, and the source region 1b and the drain region 1b of the semiconductor film 1a penetrating the interlayer insulating film 6 and the gate insulating film 2 are formed. The pole region 1c is provided with connecting openings for reaching. The data line 6a is electrically connected to the source region 1b through the connection hole, and the pixel electrode 9 is electrically connected to the drain region 1c. This TFT 30 may be either of a P-channel type or an N-channel type.

FIG. 4(c) is a schematic cross-sectional view of an inverter (CMOS-TFT) 117 provided with a data line driving circuit 17a and a scanning line driving circuit 17b. The inverter 117 has a structure in which a P-channel TFT 117P and an N-channel TFT 117N are connected to each other through an electrode (output terminal) 117c. TFT 117P and TFT 117N are formed using semiconductor film 117 s formed on TFT array substrate 11 , respectively. The gate electrode (input terminal) 117g is arranged to face the semiconductor film 117s with the gate insulating film 2 formed to cover the semiconductor film 117s interposed therebetween.

In this embodiment, the semiconductor film 1a of the TFT 30 shown in FIG. 4(b), the semiconductor film 117s of the inverter 117 shown in FIG. 4(c), and the protective circuit element 181 shown in FIG. 2(b) The semiconductor films 118s are all formed using the semiconductor films formed in the same layer on the TFT array substrate 11 . In addition, the gate electrode 3a of the TFT 30, the gate electrode 117g of the inverter 117, and the floating electrode 118g of the protection circuit element 181 are all formed on the gate insulating film (first insulating film) formed to cover the above-mentioned semiconductor film. ) 2 conductive film formation. Therefore, in any semiconductor element, the region overlapping with the semiconductor film and the gate electrode (or floating electrode) plane is an intrinsic semiconductor region or a region where a trace concentration of impurities is introduced, and a channel region 1a' and an I layer 118i are provided. wait.

In the liquid crystal display device 10 of the present embodiment having the above-mentioned structure, since the above-mentioned structure of the thin film semiconductor device is provided, the internal circuits (the data line driving circuit 17a, the scanning line driving circuit 17b, and the image display area) can be protected by the protection circuit portion 18. 17c) Protects from the image of the surge voltage introduced by the connection pad 19a. This provides a long-life liquid crystal display device that is less prone to internal circuit breakdown during manufacture and use and has excellent reliability. In addition, in the protection circuit section 18, there is an advantage that even if the input exceeds the withstand voltage of the PIN diode with such a structure and the PIN diode is destroyed, the connection pads 19a do not short-circuit to each other. It has the effect of not causing abnormal operation of the liquid crystal display device.

In addition, as described above, the semiconductor elements (TFT 30 , inverter 117 , and protection circuit element 181 ) included in the liquid crystal display device 10 are arranged in common on the conductive film with the insulating film and the semiconductor film facing each other. structure, the steps of forming the semiconductor films 1a, 117s, and 118s and the steps of forming the gate electrodes 3a, 117g, and floating electrodes 118g can be made common. In addition, even when impurities are introduced into the semiconductor film, the gate electrode 3a, 117g, and the floating electrode 118g are used as masks to implant impurities into the semiconductor film, and the channel region of the transistor and the I layer of the PIN diode can be formed in a self-matching manner. .

Therefore, in the liquid crystal display device 10 of the present embodiment, the data line driving circuit 17a, the scanning line driving circuit 17b constituting the internal circuit, and the protection circuit unit 18 functioning as an electrostatic protection circuit for the image display area 17c can be simultaneously passed through The internal circuit forming process can improve the reliability of the display device without complicating the manufacturing process.

[Second Embodiment]

Next, a second embodiment of the present invention will be described. 5 is a schematic cross-sectional view of a protection circuit element included in the thin film semiconductor device according to the second embodiment. 5 is a diagram corresponding to FIG. 2( b ) of the previous first embodiment, and the planar structure of the protection circuit element 281 according to this embodiment is basically the same as that of the protection circuit element 181 shown in FIG. 2( a ).

The protection circuit element 281 shown in FIG. 5 is mainly composed of a PIN diode 281a and a floating electrode 118g. Therefore, it is characterized in that between the I layer 118i and the N layer 118n provided at the position overlapping the semiconductor film 118s of the PIN diode 281a and the floating electrode 118g, the region with a lower impurity concentration than the N layer 118n is a low impurity region. Concentration region 218n forms the region.

FIG. 12 is a graph comparing the voltage-current characteristics of the protection circuit element according to the present embodiment and the protection circuit element according to the first embodiment. In addition, the horizontal axis represents the applied voltage, and the vertical axis represents the current. The solid line in the figure represents the characteristics of the protective element according to the first embodiment in which there is no low-concentration region between the I layer and the N layer, and the broken line represents the characteristic according to the second embodiment in which there is a low-concentration region between the I layer and the N layer. Characteristics of protective components. According to the figure, the dotted line extends to 15 V or more, and it can be seen that the withstand voltage of the protection circuit element of this embodiment is improved. A low-concentration impurity region is provided between the I layer and the N layer or between the I layer and the P layer of such a PIN diode. While the withstand voltage of the protection circuit element becomes higher, the withstand voltage of the protection circuit increases and the reliability is higher.

In this way, in TFTs used for pixel switching elements and driving circuits, in order to suppress fluctuations in electrical characteristics (threshold value V _th , transfer conductance gm, drain current I _ds, etc.) due to injection of hot carriers into the gate insulating film , using a LDD (Lightly Doped Drain) structure with a high-resistance layer near the drain to ease the electric field at the channel boundary. Therefore, the PIN diode 218n according to this embodiment has a structure in which a low-concentration impurity region (high resistance region) 218n is provided between the I layer 118i and the N layer 118n. Like the element 181, it can be easily formed in the same process as the internal circuit TFT.

[Third Embodiment]

Next, a third embodiment of the present invention will be described. 6 is a schematic cross-sectional view of a protection circuit element included in the thin film semiconductor device according to the third embodiment. FIG. 6 is a diagram corresponding to FIG. 2( b ) of the previous first embodiment, and the planar structure of the protection circuit element 381 according to this embodiment is basically the same as that of the protection circuit element 181 shown in FIG. 2( a ).

The protection circuit element 381 shown in FIG. 6 is mainly composed of a PIN diode 381a and a floating electrode 118g. Between the I-layer 118i and the N-layer 118n, which are provided on the same plane as the semiconductor film 118s and the floating electrode 118g of the PIN diode 381a, a region with a lower impurity concentration than the N-layer 118n is formed as a low-impurity-concentration region 318n. The region is the same as the PIN diode 281a shown in FIG. 5 . In the PIN diode 381a according to this embodiment, the low-concentration impurity region 318n is formed at a position overlapping the plane of the floating electrode 118g.

The structure of such a protection circuit element 381 is a structure similar to a TFT having a so-called GOLDD (Gate Overlapped Lightly Doped Drain) structure. Therefore, when the TFT constituting the internal circuit has such a GOLDD structure, even for the PIN diode 381a constituting the protection circuit element, if the low-concentration impurity region 318n in this embodiment is made so as to overlap the floating electrode plane, Even in the structure arranged in the ground, it is possible to easily form the protection circuit element in the same process as the internal circuit, and it is also possible to form the same high withstand voltage PIN diode as in the second embodiment.

In addition, in the case of forming a GOLDD structure, a structure such as a gate electrode is formed by a metal film of a two-layer structure, and the area of the metal film on the upper layer side (opposite side of the semiconductor film) of the gate is narrower than that of the metal film on the lower layer side, Impurities are introduced into the semiconductor film using the associated gate electrode as a mask. In this case, a low-concentration impurity region is formed on the semiconductor film in a self-aligning manner corresponding to the region where the metal film on the lower layer side protrudes from the metal film on the upper layer side.

Therefore, even when the protective circuit element 381 of this embodiment is manufactured, the floating electrode 118g can have the same two-layer structure as the gate electrode of the above-mentioned GOLDD structure TFT. By introducing impurities into the N layer 118n, it is possible to form the low-concentration impurity region 318n in the planar region of the floating electrode 118g.

[Fourth Embodiment]

Next, a fourth embodiment of the present invention will be described. 7 is a schematic cross-sectional view of a protective circuit element included in a thin film semiconductor device according to a fourth embodiment. FIG. 7 is a diagram corresponding to FIG. 2( b ) of the previous first embodiment, and the planar structure of the protection circuit element 481 according to this embodiment is basically the same as that of the protection circuit element 181 shown in FIG. 2( a ).

The protection circuit element 481 shown in FIG. 7 is mainly composed of a PIN diode 481a and a floating electrode 118g. The I layer 118i is provided at a position where the semiconductor film 118s of the PIN diode 481a overlaps with the floating electrode 118g on the plane, as in the previous first to third embodiments. In the present embodiment, the N layer 118n protrudes to the overlapping region of the floating electrode 118g and the semiconductor film 118s on the plane, which is different from the other embodiments. Even if the PIN diode 481a having such an N-layer overhang 418n is used, the same result as in the previous embodiment can be obtained. In addition, even if the floating electrode 118g extends to the PIN diode shown in the second and third embodiments, the PIN diode having the low-concentration impurity regions 218n and 318n between the P layer 118p and the I layer 118i, or the N layer 118n and the I layer 118i The surface of the P layer 118p or N layer 118n also has the same high withstand voltage, and can provide a protective circuit element with a protective function against reverse surge voltage.

In the previous first to third embodiments, the floating electrode 118g arranged to overlap a part of the semiconductor film 118s on the plane is used as a mask, and the case of introducing impurities into the semiconductor film is used to describe the formation of the TFT constituting the internal circuit. In the process, it is not necessary to adopt a method of forming the channel region in a self-aligning manner. For example, the photoresist patterned on the gate insulating film can also be used as a mask to introduce impurities into the semiconductor film. In this case, the gate electrode is formed after the introduction of impurities. A structure in which a portion of a region (for example, a drain region) overlaps in plane. Therefore, when the related structure is formed as an internal circuit, it is effective to use a device including the PIN diode 481 a of the present embodiment as a protection circuit element and to commonize the manufacturing process.

〔Electronic equipment〕

Next, specific examples of electronic equipment including the liquid crystal display device according to the above-mentioned embodiment of the present invention will be described.

Fig. 8 is a perspective view of an example of a mobile phone. In FIG. 8, reference numeral 1300 denotes a mobile phone main body, and reference numeral 1301 denotes a display unit using the above-mentioned liquid crystal display device. Reference numeral 1302 is an operating unit, and 1303 and 1304 are a receiving unit and a transmitting unit, respectively.

The electronic device shown in FIG. 8 has a display unit using the liquid crystal display device of the above-mentioned embodiment, and can realize a liquid crystal display unit having high reliability and long life.

In addition, the technical scope of the present invention is not limited to the limitations of the above-mentioned embodiments, and various modifications can be made without departing from the gist of the present invention. For example, the present invention is also applicable to electro-optical devices using active matrix substrates, not only liquid crystal display devices but also current-driven light-emitting devices such as organic EL displays. In addition, the arrangement of peripheral circuits such as the data line driving circuit and the scanning line driving circuit is not limited to the above-mentioned configuration, and appropriate modifications may be made.

Claims (14)

1. a thin film semiconductor device is the thin film semiconductor device that comprises matrix and be formed at the semiconductor film on this matrix, it is characterized in that,

Be provided with on the described matrix have the main circuit portion of semiconductor element, by this extended portion of terminal of main circuit portion, insert in the protective circuit portion between described main circuit portion and the described portion of terminal;

Described protective circuit portion is provided with the protective circuit element,

Described protective circuit element comprises: have the PIN diode of described semiconductor film, and between the floating electrode of the relative configuration of I layer of dielectric film and this PIN diode.

2. thin film semiconductor device according to claim 1 is characterized in that,

Constituting the semiconductor film of described PIN diode and the semiconductor film of the semiconductor element of the described main circuit of formation portion is the semiconductor film that the same one deck on described matrix forms.

3. thin film semiconductor device according to claim 2 is characterized in that,

The semiconductor element that described main circuit portion is had is a thin-film transistor,

The conducting film that constitutes the conducting film of described floating electrode and constitute the gate electrode of described thin-film transistor is formed on the same one deck on the described matrix.

4. according to each the described thin film semiconductor device in the claim 1～3, it is characterized in that,

The I layer of described floating electrode and described PIN diode is formed on the rough same position when overlooking.

5. according to each the described thin film semiconductor device in the claim 1～3, it is characterized in that,

Described PIN diode is to have the low concentration impurity zone lower than this P layer impurity concentration between its P layer and I layer, perhaps, has the low concentration impurity zone lower than N layer impurity concentration between N layer and I layer.

6. thin film semiconductor device according to claim 5 is characterized in that,

Described low concentration impurity zone be formed on described floating electrode plane in the zone that overlaps.

7. according to each the described thin film semiconductor device in the claim 1～3, it is characterized in that,

Described PIN diode and floating electrode between the relative configuration of dielectric film have and the part of the P layer of described PIN diode or N layer superposed part in the plane.

8. according to each the described thin film semiconductor device in the claim 1～3, it is characterized in that,

Described protective circuit element directly is connected with described portion of terminal.

9. the manufacture method of a thin film semiconductor device is the manufacture method that has matrix and be formed at the thin film semiconductor device of the semiconductor film on this matrix, it is characterized in that,

Described thin film semiconductor device be provided with on the matrix have the main circuit portion of semiconductor element, by this extended portion of terminal of main circuit portion, insert in the protective circuit portion between described main circuit portion and the described portion of terminal,

The operation that forms described protective circuit portion comprises: the protective circuit element forms operation,

Described protective circuit element forms operation and comprises:

On the semiconductor film that is formed on the matrix, form the operation of dielectric film;

By form on the described dielectric film conductive film pattern form with described semiconductor film plane on the operation of the floating electrode that overlaps;

By described floating electrode is imported impurity as mask in described semiconductor film, on this semiconductor film, form P layer, N layer and I layer, to form the operation of PIN diode.

10. the manufacture method of thin film semiconductor device according to claim 9 is characterized in that,

Described main circuit portion has thin-film transistor, this thin-film transistor contain comprise semiconductor film and in this semiconductor film between the relative gate electrode of dielectric film;

In same operation, form semiconductor film that constitutes described thin-film transistor and the semiconductor film that constitutes described protective circuit element; And

In same operation, form gate electrode that constitutes described thin-film transistor and the floating electrode that constitutes described protective circuit element.

11. the manufacture method of thin film semiconductor device according to claim 10 is characterized in that,

Import operation by same impurity and form the source electrode of described thin-film transistor and the P layer of described PIN diode, the perhaps drain electrode of described thin-film transistor and N layer.

12. the manufacture method of thin film semiconductor device according to claim 11 is characterized in that,

Import in the operation at described impurity, in the semiconductor film of the semiconductor film of described thin-film transistor and described protective circuit element, the low concentration impurity field that the impurity concentration of the impurity ingress area that connects near can forming is low.

13. an electro-optical device is characterized in that,

Contain each the described thin film semiconductor device in the claim 1～8.

14. an e-machine is characterized in that,

Contain the described electro-optical device of claim 13.

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