JP2007264003A - Semiconductor device, electrooptical device, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device capable of forming an accurate image even if the threshold voltage of a switching element varies with an electrification time, an electrooptical device, and electronic equipment. <P>SOLUTION: The semiconductor device includes the switching element (TFT 12) which has a functional layer formed of an organic material and includes a source electrode 16 and a drain electrode 20, and a rectifying element (diode rectifying element 14) having a P type semiconductor portion 26 and an N type semiconductor portion 28 disposed between the source electrode 16 and drain electrode 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor device, an electro-optical device, and an electronic apparatus.

2. Description of the Related Art Conventionally, an electrophoretic display device using an electrophoretic phenomenon is known as a non-light-emitting electro-optical device (see, for example, Patent Document 1). Electrophoresis is caused by fine particles (in the dispersion medium)
A phenomenon in which fine particles migrate by Coulomb force when an electric field is applied to a dispersion system in which electrophoretic particles are dispersed. Here, a schematic configuration of the electrophoretic display device will be briefly described. The electrophoretic display device is configured such that one electrode and the other electrode are opposed to each other at a predetermined interval, and a large number of dispersion systems as pixels serving as image display units are arranged in a matrix therebetween. The electrophoretic display device includes a peripheral circuit for applying an electric field to the dispersion system.

FIG. 11 is a cross-sectional view of a main part of a display panel showing a dispersion system corresponding to one pixel of the electrophoretic display device. In the dispersion system 56 serving as a pixel, a partition wall 42 is formed between the electro-optical device substrate 58 provided with the pixel electrode 20 and the like and the counter substrate 40 provided with the common electrode 38 and the like, and both the electrodes 20 and 38 and the partition wall 42 are formed. Are filled with a liquid (dispersion medium) 48 in which electrophoretic particles 46 are dispersed. As the common electrode 38 and the counter substrate 40, a material having transparency is used. Here, for example, when realizing binary display, the dispersion medium 48 is dyed black, and the electrophoretic particles 46 are white particles such as titanium oxide. The electrophoretic particles 46 are charged so as to have either a positive or negative charge. Also, the electro-optical device substrate 5
In addition to the pixel electrode 20 described above, a thin film transistor (hereinafter referred to as TFT) functioning as a scanning line, a data line, and a switching element is formed in FIG.
1 is omitted).

FIG. 12 is an explanatory diagram for explaining an equivalent circuit corresponding to one pixel. That is, the gate line 18 and the data line 1 are formed on the electro-optical device substrate 58 of the display panel along directions orthogonal to each other.
6 are provided, and TFTs 12 are provided corresponding to the intersections thereof. The gate electrode of the TFT 12 is connected to the gate line 18. The source electrode of the TFT 12 is the data line 1
6 is connected. Further, the drain electrode of the TFT 12 is connected to one pixel electrode 20 that sandwiches the dispersion system 56. A common voltage Vcom (generally a ground voltage) is applied to the other common electrode 38 sandwiching the dispersion system 56.

In such a configuration, the gate line 18 is activated by a gate line signal supplied from a scanning line driving circuit (not shown), and the TFT 12 is turned on during this active period (selection period). A voltage is applied to the pixel electrode 20 by supplying a data signal from a data line driving circuit (not shown) via the data line 16 and the turned-on TFT 12.

When a potential difference is applied between the pixel electrode 20 and the common electrode 38, the electrophoretic particles 46 are attracted to either the pixel electrode 20 or the common electrode 38 by Coulomb force. At this time, when the electrophoretic particles 46 are attracted to the transparent common electrode 38 side, the light incident from the common electrode 38 is reflected by the electrophoretic particles 46 and the color (white) of the electrophoretic particles 46 can be seen. On the other hand, when the electrophoretic particles 46 are attracted to the pixel electrode 20 side, the incident light and the reflected light described above are absorbed by the dispersion medium 48, and the color (black) stained by the dispersion medium 48 is seen. That is, the electrophoretic display device forms an image by individually controlling the movement positions of the electrophoretic particles 46 of the dispersion system 56 for each of the dispersion systems 56 arranged in a matrix on the display panel. .

JP 2002-169190 A

However, the voltage value supplied from the gate line 18 to the gate electrode of the TFT 12 is TF.
The voltage between the pixel electrode 20 and the common electrode 38 sandwiching the dispersion system 56 is determined from the power supply voltage because the voltage for turning on T12 (0V) and the voltage for turning off the TFT 12 (power supply voltage) are two values. A voltage obtained by subtracting the threshold voltage cannot be obtained. So T
If the threshold voltage of the FT 12 is measured, and the threshold voltage is subtracted from the voltage to be turned off and applied to the gate electrode, the power supply voltage can be made between the pixel electrode 20 and the common electrode 38. When the threshold voltage of the TFT 12 fluctuates due to external factors such as the passage of time with the passage of energization time, an overvoltage is applied to the gate terminal when the threshold voltage decreases, and the TFT 1
When the gate breakdown of 2 is caused or the threshold voltage is increased, an accurate image cannot be formed due to insufficient voltage.

The present invention has been made to solve the above-described problems, and can provide an accurate image even when the threshold voltage of the switching element fluctuates with the passage of energization time, and an electro-optical device. To provide electronic equipment.

(1) In the semiconductor device according to the present invention, a functional layer is formed of an organic material, a switching element including a source electrode and a drain electrode, and a P type disposed between the source electrode and the drain electrode A rectifying element including a semiconductor portion and an N-type semiconductor portion. According to the present invention,
Even if the threshold voltage of the switching element fluctuates due to the passage of energization time, the gate of the switching element can be prevented and the power supply voltage can be set between the pixel electrode and the common electrode, so that an accurate image can be formed.

(2) In this semiconductor device, the constituent material of the N-type semiconductor portion may be formed of an n-type oxide semiconductor material, and the P-type semiconductor portion may be formed of copper iodide or an organic semiconductor.

  (3) In this semiconductor device, the N-type semiconductor portion may be formed of a dense film.

  (4) In this semiconductor device, a porous body may be formed on the dense film.

(5) In this semiconductor device, one of the P-type semiconductor portion and the N-type semiconductor portion is in contact with the source electrode, and the other of the P-type semiconductor portion and the N-type semiconductor portion is in contact with the drain electrode. May be.

(6) The semiconductor device may further include a light shielding layer that covers the P-type semiconductor portion and the N-type semiconductor portion.

(7) An electro-optical device according to the present invention includes the semiconductor device and an electro-optical element driven by the semiconductor device.

  (8) An electronic apparatus according to the invention includes the electro-optical device.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
(Semiconductor device)
FIG. 1 is a plan view showing a main part of an electro-optical device substrate according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a cross-sectional configuration in the vicinity of the semiconductor device provided in the electro-optical device substrate according to the embodiment of the present invention. With reference to FIG. 1 and FIG. 2, a configuration of a substrate for an electro-optical device as a semiconductor device according to the present embodiment will be described. In addition, in each figure, in order to make each layer and each member the size which can be recognized on drawing, the scale is varied for every layer and each member.

The electro-optical device substrate 2 according to the present embodiment includes a substrate 10 as shown in FIGS.
T as a switching element (active matrix element) forming the main part of the semiconductor device
An FT (thin film transistor) 12, a diode rectifier element 14 as a rectifier element, a data line 16, a gate line 18, and a pixel electrode 20 are mainly configured.

The TFT 12 has a function of switching and driving the pixel electrode 20. As shown in FIG. 2, the source electrode 16, the drain electrode 20, the gate insulating film 24, the gate electrode 18,
It is mainly composed of a semiconductor layer (not shown). Here, the source electrode 16 and the drain electrode 20 are formed in a comb shape near the connection with the TFT 12, thereby facilitating alignment when forming the TFT 12. In addition, the semiconductor layer (functional layer) is made of an organic material, and is specifically configured using a polymer semiconductor material. Data line 16
The gate line 18 is a wiring that is electrically connected to the TFT 12 and supplies an electrical signal to the TFT 12. Here, the pixel electrode 20 is directly connected to the TFT 12, and in this case, the pixel electrode 20 functions as the drain electrode 20 of the TFT 12. The gate line 18 functions as a wiring for supplying a scanning signal to the TFT 12.

The diode rectifying element 14 has a P-type semiconductor portion 26 and an N-type semiconductor portion 28. The diode rectifying element 14 is formed by electrically connecting a P-type semiconductor part 26 and a drain electrode 20, and an N-type semiconductor part 28 and a source electrode 16 between a source electrode 16 and a drain electrode 20 of the TFT 12. .

The constituent material of the P-type semiconductor unit 26 may be formed of copper iodide or an organic semiconductor. The constituent material of the N-type semiconductor portion 28 may be formed of an n-type oxide semiconductor material. For example, titanium dioxide (TiO2), titanium monoxide (TiO), dititanium trioxide (
Examples thereof include titanium oxide such as Ti2O3), n-type oxide semiconductor materials such as zinc oxide (ZnO) and tin oxide (SnO2), and other n-type semiconductor materials. Among these, one kind or a combination of two or more kinds can be used. Among these, it is preferable to use titanium oxide, particularly titanium dioxide.

That is, it is preferable that the N-type semiconductor portion 28 is mainly composed of titanium dioxide. Since the crystal structure of titanium dioxide is stable, the N-type semiconductor portion 28 mainly composed of titanium dioxide has little secular change (deterioration) even when exposed to a harsh environment, and has stable performance. It has the advantage that it can be obtained continuously for a long time. Titanium dioxide is mainly composed of anatase-type titanium dioxide, mainly rutile-type titanium dioxide, or a mixture of anatase-type titanium dioxide and rutile-type titanium dioxide. Any of those may be used. Due to the relatively unstable crystal structure of the anatase-type titanium dioxide, the N-type semiconductor portion 28 mainly composed of the anatase-type titanium dioxide has an advantage that electrons are easily generated. In addition, when mixing rutile type titanium dioxide and anatase type titanium dioxide, the mixing ratio of rutile type titanium dioxide and anatase type titanium dioxide is not particularly limited. It is preferably about 5:95, and more preferably about 80:20 to 20:80.

The N-type semiconductor unit 28 may be formed of a dense film 30. Further, a nanoparticle porous body 32 may be formed on the dense film 30 (see FIG. 3). Leakage current can be suppressed by providing the dense film 30. By forming the dense film 30, the leakage current of the forward bias is reduced and the leakage current is prevented from flowing in the reverse direction.

The forward voltage of the diode rectifier element may be smaller than the initial threshold voltage Vth of the TFT 12. Further, the forward voltage of the diode rectifying element may be smaller than the threshold voltage Vth at which the threshold voltage of the TFT 12 changes as the energization time elapses.

In the diode rectifying element, an N-type semiconductor portion 28 is provided on the back surface of the substrate 10 via the conductor layer 22, a hole is formed in the substrate 10, and the P-type semiconductor portion 26 is contacted using P-type semiconductor ink. Good (see FIG. 4). The material of the P-type semiconductor part 26 is, for example, F8T2 (fluorene-bithiophene copolymer).

In the electro-optical device substrate 2 configured as described above, the data line 16 is electrically connected to the TFT 12, and image signals (data signals) are sequentially supplied to the data line 16, or mutually. Each group is supplied to a plurality of adjacent data lines 16. Further, the gate line 18 is electrically connected to the TFT 12, and a scanning signal is supplied to the plurality of gate lines 18 in a pulse-sequential manner at a predetermined timing. Further, the pixel electrode 20 functions as the drain electrode 20 of the TFT 12, and a pulse voltage is applied to the gate electrode 18 to turn on the TFT 12 for a certain period of time.
The image signal supplied from 6 is written to the pixel electrode 20 at a predetermined timing.

Next, a method for manufacturing the diode rectifying element 14 of the electro-optical device substrate 2 will be described with reference to FIG. A source electrode 16 (data line 16), a drain electrode 20 (pixel electrode 20), and the like are already formed on the substrate 10.

First, an electrode is provided on the extension of the source electrode 16 (data line 16), and the N-type semiconductor portion 28 is formed on the electrode (step S100). The N-type semiconductor unit 28 may be formed of a dense film 30. Furthermore, a nanoparticle porous body 32 may be formed on the dense film 30 (
(See FIG. 3). The dense film 30 can be formed using, for example, a sputtering method, a MOD method, or the like.

Next, the P-type semiconductor portion 26 is formed on the upper surface of the N-type semiconductor portion 28 so that one end thereof is electrically connected to the drain electrode 20 (pixel electrode 20) (step S110). As a method for forming the P-type semiconductor portion 26, for example, a wet method such as a spin coating method or an ink jet method can be used.

Next, the P-type semiconductor unit 26 is dried (step S120). The P-type semiconductor unit 26
After drying, a light shielding layer 34 (see FIG. 2) may be formed so as to cover the diode rectifier element 14. By providing the light shielding layer 34, light can be transmitted to the P-type semiconductor unit 26 or the N-type semiconductor unit 2.
Therefore, it is possible to suppress malfunction caused by light generated by light. The material of the light shielding layer 34 may be an epoxy material or the like.

Thereafter, the gate insulating film 24, the gate electrode 18 (gate line 18) and the like are sequentially formed by a known manufacturing method.

Through the above steps, the electro-optical device substrate 2 including the TFT 12 and the diode rectifying element 14 is formed. In this embodiment mode, a wet method (liquid phase process) is employed in a series of steps, so that a film can be formed in an atmospheric pressure atmosphere without using a vacuum apparatus, and manufacturing costs can be reduced. it can. In particular, in the process of forming the TFT 12 and the diode rectifying element 14 excluding the pixel electrode 20, since an organic material is mainly used, manufacturing by a liquid phase process is preferable, and the manufacturing process is very simple.
(Electro-optical device)
Next, the electro-optical device according to this embodiment will be described with reference to FIG. Here, an electrophoretic display device configured using the above-described electro-optical device substrate 2 will be described as an electro-optical device. FIG. 6 is a cross-sectional view showing a main part of the electrophoretic display device according to the embodiment of the present invention.

As shown in FIG. 6, the dispersion system 36 of the electrophoretic display device 4 according to the present exemplary embodiment includes an electro-optical device substrate 2 provided with the diode rectifying element 14, the pixel electrode 20, and the like, and a common electrode 38.
Are arranged in a region partitioned by a partition wall 42 between the counter substrate 40 and the like. That is, the dispersion system 36 has electrophoretic particles 46 in a space 44 formed by the electrodes 20 and 38 and the partition walls 42.
And a liquid (dispersion medium) 48 in which is dispersed. As the common electrode 38 and the counter substrate 40, a material having transparency is used. Here, for example, when realizing binary display, the dispersion medium 48 is dyed black, and the electrophoretic particles 46 are white particles such as titanium oxide. The electrophoretic particles 46 are charged so as to have either a positive or negative charge.

In addition to the above-described diode rectifying element 14 and pixel electrode 20, the electro-optical device substrate 2 is formed with a gate line 18, a data line 16, and a TFT 12, as shown in FIG.

Next, the operation of the TFT 12 for controlling the dispersion system will be described with reference to FIG. FIG.
FIG. 5 is an equivalent circuit diagram of a display area for explaining the operation of the TFT 12 that controls the dispersion system 36 according to the embodiment of the present invention. In the present embodiment, it is assumed that the conductivity type of the TFT 12 is a p-channel type and is composed of an organic TFT.

FIG. 7A is an equivalent circuit diagram of the display area for explaining the operation (data writing) for attracting the electrophoretic particles 46 of each dispersion system 36 to the common electrode 38 side, and FIG. FIG. 6 is an equivalent circuit diagram of a display area for explaining an operation (data clear) that is drawn toward the pixel electrode 20 side.

At the time of data writing, as shown in FIG. 7A, the common voltage Vcom is set to the ground potential (0 V).
), The data line 16 is a power supply potential (VDD, for example, 40V), and the gate line 18 is a ground potential (0V).
), Respectively. In this state, VDD is applied to the source electrode 16 of the TFT 12 and 0 V is applied to the gate electrode 18, so that the TFT 12 is turned on, and the drain electrode 20 of the TFT 12 becomes VDD after the dispersion system 36 is charged.

Next, the operation in the prior art and the operation of the electrophoretic display device 4 according to the present embodiment will be described for the operation at the time of data clear.

At the time of data clear in the prior art, the common voltage Vcom is set to VD as shown in FIG.
D, the data line 16 is set to 0V, and the gate line 18 is set to 0V. In this state, 0 V is applied to the source electrode 16 of the TFT 12 and 0 V is applied to the gate electrode 18.
2 is turned on, but the drain electrode 20 of the TFT 12 does not change to 0 V even after the dispersion system 36 is charged, and remains at the threshold voltage Vth of the TFT 12. For this reason, since the potential difference between the pixel electrode 20 and the common electrode 38 of the dispersion system 36 is VDD−Vth, the operation of attracting the electrophoretic particles 46 of the dispersion medium 48 toward the pixel electrode 20 becomes slow or sufficiently attracted. There was no problem.

In order to solve this problem, a potential of −Vth may be applied to the gate terminal of the TFT 12. For example, a so-called organic TFT in which a semiconductor layer is formed of an organic material or an amorphous structure in which a semiconductor layer is formed of amorphous silicon. The threshold voltage of the silicon TFT changes as the energization time increases. Since a so-called threshold voltage shift is significant, it is difficult to set a voltage to be applied to the gate terminal as -Vth. If -Vth is uniformly applied to the gate terminal, the gate voltage may be destroyed if the threshold voltage becomes lower than the original Vth.

FIG. 8 is a diagram showing Vds-Ids characteristics at each gate potential of the TFT. As shown in FIG. 8, when Vds is 20 V or less, Ids hardly flows. The reason why the threshold voltage of the TFT changes as the energization time elapses is that there is an electron donating property due to adsorption of water molecules, ions, etc. to the semiconductor interface (underlayer to semiconductor interface, or gate insulating layer to semiconductor interface). It is possible that electron acceptability is developed.

At the time of data clear in the electrophoretic display device 4 according to the present embodiment, as shown in FIG. 7B, the common voltage Vcom is set to VDD, the data line 16 is set to 0V, and the gate line 18 is set to 0V. In this state, VDD is applied to the anode electrode of the diode rectifier element 14 and 0 V is applied to the cathode electrode, so that the diode rectifier element 14 is turned on and the TFT
The twelve drain electrodes 20 become VDD after a period in which the dispersion system 36 is charged.

According to the embodiment described above, the following effects can be obtained. In this embodiment, even if the threshold voltage of the TFT 12 as a switching element fluctuates with the passage of energization time, the TFT
12 can be prevented and the power supply voltage can be set between the pixel electrode and the common electrode, so that an accurate image can be formed.
(Electronics)
The electrophoretic display device 4 according to this embodiment described above can be applied to various electronic devices including a display unit. Hereinafter, an example of the electronic device will be described.

First, an example in which the electrophoretic display device 4 according to the present embodiment is applied to flexible electronic paper will be described. FIG. 9 is a view showing electronic paper according to the embodiment of the present invention. The electronic paper 6 includes the electrophoretic display device according to the present embodiment as the display unit 50. The electronic paper 6 includes a main body 52 made of a rewritable sheet having the same texture and flexibility as conventional paper.

FIG. 10 is a diagram showing an electronic book according to an embodiment of the present invention. Electronic notebook 8
In FIG. 9, a plurality of electronic papers 6 shown in FIG. 9 are bundled and sandwiched between covers 54. The cover 54 includes display data input means (not shown) for inputting display data sent from an external device, for example. Thereby, according to the display data, the display content can be changed or updated while the electronic paper is bundled.

In addition to the examples described above, other examples include personal computer monitors, mobile phones, LCD TVs, viewfinder type and monitor direct view type video tape recorders, car navigation devices, pagers, electronic notebooks, calculators, word processors, works Station, video phone,
Examples include a POS terminal and a device equipped with a touch panel. The electro-optical device according to this embodiment can be used as a display portion of such an electronic apparatus.

In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and results). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. Also,
The present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment. Furthermore, the present invention includes contents that exclude any of the technical matters described in the embodiments in a limited manner. Or this invention includes the content which excluded the well-known technique limitedly from embodiment mentioned above.

FIG. 4 is a plan view illustrating a main part of the electro-optical device substrate according to the embodiment of the invention. 1 is a cross-sectional view showing a cross-sectional configuration in the vicinity of a semiconductor device provided on an electro-optical device substrate according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a main part of a substrate for an electro-optical device according to an embodiment of the invention. FIG. 3 is a cross-sectional view illustrating a main part of a substrate for an electro-optical device according to an embodiment of the invention. It is a figure which shows the manufacturing method of the board | substrate for electro-optical apparatuses which concerns on embodiment of this invention. It is sectional drawing which shows the principal part of the electrophoretic display device which concerns on embodiment of this invention. FIG. 5 is an equivalent circuit diagram of a display area for explaining the operation of the TFT for controlling the dispersion system according to the embodiment of the present invention. It is a figure which shows the Vds-Ids characteristic in each gate electric potential of TFT which controls the conventional dispersion system. It is a figure which shows the electronic paper which concerns on embodiment of this invention. It is a figure which shows the electronic book which concerns on embodiment of this invention. It is principal part sectional drawing of the display panel which shows the dispersion system corresponding to 1 pixel of the electrophoretic display apparatus in a prior art. It is explanatory drawing explaining the equivalent circuit corresponding to 1 pixel in a prior art.

Explanation of symbols

2 ... Electro-optical device substrate 4 ... Electrophoretic display device 6 ... Electronic paper 8 ... Electronic notebook
DESCRIPTION OF SYMBOLS 10 ... Substrate 12 ... TFT (thin film transistor) 14 ... Diode rectifier 16 ... Source electrode (data line) 18 ... Gate electrode (gate line) 20 ... Drain electrode (pixel electrode) 22 ... Conductor layer 24 ... Gate insulating film 26 ... P Type semiconductor part 28... N type semiconductor part 3
DESCRIPTION OF SYMBOLS 0 ... Dense film 32 ... Porous body 34 ... Light shielding layer 36 ... Dispersion system 38 ... Common electrode 40 ... Opposite substrate 42 ... Partition 44 ... Space 46 ... Electrophoretic particle 48 ... Liquid (dispersion medium) 50 ... Display part 52 ... Main body 54 ... Cover 56 ... Dispersion system 58 ... Electro-optical device substrate.

Claims (8)

A switching element having a functional layer formed of an organic material and including a source electrode and a drain electrode;
A rectifying device including a P-type semiconductor portion and an N-type semiconductor portion disposed between the source electrode and the drain electrode;
A semiconductor device comprising: The semiconductor device according to claim 1,
The constituent material of the N-type semiconductor part is formed of an n-type oxide semiconductor material, and the P-type semiconductor part is formed of copper iodide or an organic semiconductor. The semiconductor device according to claim 1 or 2,
The semiconductor device, wherein the N-type semiconductor portion is formed of a dense film. The semiconductor device according to claim 3.
A semiconductor device, wherein a porous body is formed on the dense film. The semiconductor device according to any one of claims 1 to 4,
One of the P-type semiconductor portion and the N-type semiconductor portion is in contact with the source electrode, and the P-type semiconductor portion
The other of the n-type semiconductor portion and the n-type semiconductor portion is in contact with the drain electrode. The semiconductor device according to any one of claims 1 to 5,
A light shielding layer covering the P-type semiconductor portion and the N-type semiconductor portion;
A semiconductor device characterized by the above. A semiconductor device according to any one of claims 1 to 6;
An electro-optical device comprising: an electro-optical element driven by the semiconductor device. An electronic apparatus comprising the electro-optical device according to claim 7.

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