JP3688699B2 - Electrical equipment - Google Patents

Description

  The present invention relates to a liquid crystal display device or a similar display device. The present invention particularly relates to an active matrix display device, a display method thereof, and a manufacturing method thereof. One of the objects of the present invention is a display for black and white display, and relates to a display that requires high visibility and low cost, instead of requiring high-level operation and high-speed operation such as gradation display. In particular, a display having such a function is used for a read-only display device such as various information displays.

  With recent miniaturization and power saving of various OA devices, display devices are being replaced from conventional cathode ray tubes (CRT) to flat panel displays (FPD) such as liquid crystal displays (LCD) and plasma displays. . In particular, LCDs are used in portable devices because of their low power consumption.

  However, LCD still has many problems to be solved. Currently used LCDs are called simple matrix LCDs, and are sometimes called STNLCDs after taking the name of liquid crystal material. Since STNLCD is easy to manufacture, the cost is low and it is widely used.

  However, the STN as a liquid crystal material has a problem that the response speed, which is an original characteristic of the material, is extremely slow, and when an object that moves at high speed is displayed, the object cannot follow and cannot be displayed.

  From the operation method, the time during which one pixel is lit in one frame (usually 10 to 30 msec) is from several tens of μsec to several msec. This is inversely proportional to the number of rows in the matrix, and in a 200-row matrix, only about 150 μsec is lit as 30 msec per frame. For this reason, the contrast of the screen is low, and it has the disadvantages that it is very difficult to see when the screen is viewed obliquely. Furthermore, if there is a very bright or dark part of the screen, a phenomenon (crosstalk) occurs that affects the surrounding area.

  On the other hand, in recent years, LCDs having a method of having an active element in each pixel and thereby switching the pixel have been proposed and are commercially available. These are collectively referred to as an active matrix LCD, but are referred to as TFTLCD or MIMLCD depending on the type of active element. The TFT is a thin film transistor, and the MIM is a diode having a metal / insulator / metal structure.

  In these LCDs, the pixel lighting time during one frame is almost equal to one frame, so the contrast is high and the viewing angle is wide. However, due to technical problems, the production yield is low, the cost and the selling price are high, and at present, it is practically used only for the display of a high-class computer.

  In addition, the current demand for LCD is mainly used for portable computers, but in the future, a wider range of applications is expected. For example, there are uses such as a cordless phone, a display attached to a mobile phone, or an information display such as a portable electronic dictionary. In such a case, visibility and low price are required, and further power saving is required. However, conventional LCDs are not satisfactory in that respect.

  For example, although the cost of STNLCD is low, it is difficult to see from the above problems. There are two types of TFTLCDs: TFTLCDs using TFTs using amorphous silicon (hereinafter referred to as a-Si TFTLCDs) and TFTLCDs using TFTs using polysilicon (hereinafter referred to as polysilicon TFTLCDs). Both the former and the latter have no problem in viewability of the image, but the STNLCD cannot compete with the cost.

  In particular, when an a-Si TFT LCD is used as a small read-only display, one of the most cost-increasing factors is that the drive circuit cannot be built in, so the driver IC must be connected by the TAB method or the like. Expenses will become a major part of the cost increase.

  FIG. 3 shows the relationship between the number of pixels (number of dots) of the LCD and the cost. This relationship is conceptual and semi-quantitative. In a simple matrix system such as STNLCD, the matrix itself is relatively easy to manufacture, and most of the cost of the small-scale matrix is occupied by the driver IC. That is, the number of driver ICs is proportional to the number of terminals in the matrix, while the number of dots is proportional to the square of the number of terminals, and the price of the driver IC is proportional to the square root of the number of dots. Cost is controlled by the price of. This is shown in the simple matrix: TAB in the figure.

  In the a-Si TFT LCD, the production of the matrix is complicated and the yield of itself is low, and the whole is shifted upward as compared with the simple matrix. The situation is shown in a-SiTFT: TAB in the figure. In the a-Si TFT LCD, the elements occupying the price are different between the small matrix and the large matrix. In the small-scale matrix, the price of the driver IC occupies a large part of the cost as in the STNLCD. On the other hand, in a large-scale matrix, the cost due to a decrease in matrix yield is a major factor.

  In the polysilicon TFT LCD, the driver IC can be manufactured simultaneously with the matrix formation by using polysilicon, so that it is not necessary to mount the IC, and therefore the driver IC does not enter the cost factor. In particular, the mounting of the driver IC is technically problematic, and the purpose of thinking about miniaturization is not originally suitable. Therefore, the polysilicon TFT LCD is also characterized in that it can be miniaturized. However, the polysilicon TFTLCD is more difficult to produce the matrix itself than the a-Si TFTLCD, and the cost increases remarkably as the number of dots increases. However, since there is no cost factor for the driver IC in the small-scale matrix, the cost is competitive with the a-Si TFT LCD as shown in the complete polysilicon TFT in the figure.

  Now, an a-Si TFT LCD can compete with an STN LCD as shown by a dotted line (complete a-Si TFT) in the figure if the driver can be composed of a-Si. However, this is not possible with the conventional TFT LCD system. That is, for example, when a relatively small matrix of 160 × 100 is considered, since the frame frequency is 30 Hz in normal operation, a signal of 480 kHz is input especially to the data line driver. However, the a-Si TFT cannot follow such high speed operation. The same applies to compound semiconductors such as cadmium selenium (CdSe) based semiconductors. In the background that these semiconductor materials are not actively used as active elements, there are toxic and resource problems, but the low response speed is also a serious problem.

  To avoid this difficulty, the frame frequency may be lowered. In particular, when it is not necessary to display a moving image, it seems that there is no problem with a decrease in the frame frequency. However, due to the technical problem of the current TFTLCD, the state of frame scanning is visible and the screen is extremely It becomes difficult to see.

  FIG. 2 shows a pixel circuit of a TFTLCD using TN liquid crystal as a conventional liquid crystal material and an operation example thereof. The gate electrode of the TFT is connected to a selection line (also called a gate line), the drain is connected to a data line (also called a drain line), and the source is connected to a pixel electrode. The counter electrode of the pixel electrode is normally kept at a constant voltage as a common electrode. Generally grounded.

  As shown in FIG. 2B, a pulse is periodically applied to the selection line, and pixel information is applied to the data line as a voltage signal. The pulse period of the selection line is a period of one frame in a normal operation, and is typically 10 to 30 msec. The pulse width is about the period divided by the number of rows of the matrix or less, and is 100 to 300 μsec in a relatively small 100-row matrix used for information display, for example.

  The signal on the data line is in a voltage state when the pixel is turned on, and in a non-voltage state when the pixel is turned off. Also, the polarity of the voltage state is periodically switched. This is because, when a direct current is applied to the TN liquid crystal material for a long time, it causes electrolysis and deteriorates. This operation is called alternating current.

Now, the signal on the source side of the TFT to which such a signal is applied becomes as indicated by V ₁ . First, by applying the pulse of the selection line, the TFT is turned on, and the source voltage rises to be the same as the drain voltage. However, at the same time that the pulse is cut off, there is a voltage effect of ΔV due to the parasitic capacitance between the gate electrode and the source region of the TFT. After that, since the TFT is turned off, the pixel electrode is in an electrically floating state, and the voltage gradually decreases due to the leakage current of the TFT.

Next, when a pulse is applied to the selection line again and the TFT is turned on, the source voltage approaches the negative drain voltage this time. Thereafter, the pulse is cut off, and the voltage is negatively shifted by ΔV due to the parasitic capacitance, and the voltage is attenuated by the leakage current. When the last selection line pulse is applied, the drain voltage is 0, so the charge stored in the pixel electrode is released and V ₁ becomes 0.

  If the frame frequency is lowered, such voltage fluctuation becomes visible at the frame frequency. The decrease in frame frequency is limited to 10 Hz.

  Another solution is to make only the driver IC with polysilicon, but in order not to limit the type of glass substrate, annealing at a high temperature as usual is not possible, so laser annealing, etc. Advanced technology must be adopted. However, laser annealing has not been established yet and is inferior in mass productivity.

  The present invention provides a new active matrix system capable of competing with the simple matrix system in terms of cost and capable of realizing an image quality equivalent to that of the active matrix system, and a display device thereof, particularly in a display device that does not need to display moving images. It is.

  In particular, the present invention eliminates the need for a driver IC by simultaneously forming a pixel matrix and a peripheral driver circuit using a-Si TFTs or similar TFTs that can be manufactured at a relatively low temperature, thereby improving yield and reducing costs. To do.

  As described above, especially in a display that does not need to display a moving image, the frame frequency is lowered when a TFT using a low mobility semiconductor such as an a-Si TFT or a CdSe-based semiconductor is used in a driver circuit. It is an important method. However, a reduction in frame frequency should not cause visible image quality degradation such as flicker.

  By the way, in the conventional idea, the meaning of the frequency of alternating current and the meaning of the rewriting frequency overlapped with the frame frequency. Even if both were separated, it was natural that the rewrite frequency was higher than the AC frequency. Note the word “rewrite” used in the text. In this text, rewriting does not only mean a change in display content, but it means that a signal is newly injected from outside or there is an opportunity even if the display content is the same. Therefore, in a conventional TFT LCD, a pixel that is lit in a certain frame maintains a lit state in the next frame. Therefore, a pulse is applied to the selection line and a signal is sent to the data line at the same time. Let us say that it has been rewritten.

  As described above, the frame frequency cannot be 10 Hz or less due to visual problems. In the present invention, it is intended to solve the above-mentioned problems by clearly distinguishing between alternating current and rewriting and controlling both independently. If these elements are separated, it will be clear that it is the alternating frequency that affects the vision, not the rewriting frequency. For example, in a segment type LCD, the rewriting operation is substantially different from the AC operation. In fact, the frequency of rewriting the calculator's LCD is very slow. However, the frequency of alternating current is about 30 Hz. The reason why the display on the LCD flickers due to battery depletion or the like is due to a decrease in the AC frequency, not because the cycle of rewriting has decreased.

  Also in the present invention, in order to prevent flickering, the alternating frequency must be 10 Hz or more. However, the rewriting frequency needs to be 1 Hz or less.

  For example, if rewriting is 1 Hz, the signal sent to the driver of the data line of the LCD of 160 × 100 dots is 1/30 of the conventional 16 kHz, which is a speed that can be sufficiently driven even by the a-Si TFT.

  In order to achieve such an object, the conventional TFT LCD system is extremely inappropriate. This is because in the conventional TFT LCD, one TFT has two roles of pixel selection and voltage supply to the pixel. Therefore, in the present invention, these two roles are separated from each active element. Here, an element that selects a pixel is a first element, and an element that receives the output of the first element and supplies a voltage to the pixel is a second element.

  These elements are constituted by active elements such as TFTs and various diodes, or passive elements such as resistors and capacitors. In these productions, those produced under a-Si or equivalent conditions are desired, and the use of a high-temperature process at 600 ° C. or higher is avoided.

Most simply, as shown in FIG. 1A, the two TFTs are the first element (Tr ₁ ) and the second element (Tr ₂ ), respectively. In the present invention, it is necessary to provide a voltage supply line that does not exist in the conventional TFT LCD system in the sense that alternating current is performed regardless of pixel rewriting. As shown in the drawing, _one of the source and drain of Tr ₁ is connected to the data line, the gate electrode is connected to the selection line, and the other of the source and drain is connected to the gate electrode of Tr ₂ as shown in the figure. One of the source and drain of Tr ₂ is connected to the voltage supply line, and the other of the source and drain is connected to the pixel electrode.

  The operation of this example will be described below with reference to FIG. Here, for the sake of simplicity, it is assumed that rewriting is performed once while AC is performed twice. Of course, the case where the rewriting is performed once while the AC is performed 10 times or the case where the rewriting is performed once while the AC is performed 30 times can be similarly expanded.

In this example, it is assumed that the pixel that was initially turned off is turned on and turned off again at the next rewriting. The select line V _G, a pulse as in the prior art are regularly applied. On the other hand, necessary signals are also applied to the data lines. The signal applied to the data line is a binary value of positive and negative, or a binary value of a voltage state and a non-voltage state. Here, it is assumed that both Tr ₁ and Tr ₂ are NMOS. In addition, the potential of the counter electrode of the pixel is set to zero.

When a pulse is first applied to the selection line, since the signal on the data line is positive, the potential V1 on the source side of Tr ₁ becomes a positive value, and the voltage increases as in the case of the conventional TFTLCD. It falls at the end of the pulse, and then discharges spontaneously. The time required for this discharge is determined by the OFF resistance of Tr ₁ and the capacitance C between the gate electrode of Tr ₂ and the channel. For example, in the a-Si TFT, the OFF resistance is about 10 ¹³ Ω and the C is about 10 ⁻¹³ F, so the attenuation constant is about 1 second. That is, the voltage is about 40% after 1 second. It is also possible to extend this time by increasing C.

  On the other hand, a signal synchronized with the pulse of the selection line is sent to the voltage supply line, but an AC pulse is sent to the voltage supply line as shown in FIG. Here, for each selection pulse, the signal polarity of the voltage supply line changes twice, positive and negative. Of course, the polarity may be changed more for one selection pulse.

Since the gate electrode of Tr ₂ already takes a positive voltage, Tr ₂ is turned ON, the voltage of the voltage supply line is directly applied to the pixel electrode, the voltage V ₂ of the pixel electrode, FIG. 1 (B As shown in (1), it first takes a negative value, and then takes a positive value as the voltage of the voltage supply line is inverted. As can be said to be a feature of the present invention, the pixel is supplied with substantially the same voltage as the voltage of the voltage supply line by such a two-step operation, and this is caused by natural discharge as in the prior art. There is no decrease. Therefore, black and white is clearly discriminated.

Next, a pulse is again applied to the selection line. At this time, since the voltage of the data line is 0, the electric charge stored in C is discharged and V ₁ becomes 0. As a result, Tr _{2 is} also turned off, and the supply of voltage to the pixel is stopped.

  In the prior art, since the AC cycle was the same as or longer than the rewrite cycle, it was necessary to apply a pulse as shown by a dotted line to the selection line. However, according to the present invention, the pulse is unnecessary and the operation signal is halved.

  Considering the effect of the present invention further, for example, if rewriting is performed once per second by the same method as in FIG. 1, this is 1/30 of the conventional speed. This means that both the pulse applied to the selection line and the data line signal can be 30 times longer. For example, in the case of a pulse of a selection line, the conventional method has been about 100 μsec in a 200-row matrix, but in the present invention, it can be 30 times 3 msec. This means that even if the operation of the TFT is slow, it is possible to charge and supply the necessary voltage in a reliable response. Conventionally, since the response of the a-Si TFT was difficult in a short time, due to variations in characteristics of each TFT, a sufficiently charged pixel and a non-charged pixel were generated, leading to deterioration in image quality.

  In the present invention, a semi-analog voltage is not applied to the pixel by the operation of the two-stage TFT. However, such a feature reduces TFT defects and contributes to an improvement in yield.

In this description, it is desirable to use an a-Si TFT as the TFT. In either case, an NMOS a-Si TFT may be used, but an enhancement type TFT may be used for Tr ₁ and a depletion type TFT may be used for Tr ₂ . When an a-Si TFT is used, PMOS is not suitable for the purpose because its operation speed is extremely slow. However, in a silicon semiconductor in an intermediate state between amorphous silicon and polysilicon, the mobility of holes is considerably large, so that PMOS can be used. In that case, the peripheral circuit can also be a CMOS.

  An example of the overall configuration of the apparatus of the present invention is shown in FIG. The number of dots of this LCD is, for example, 320 × 480 (half the screen of a normal laptop computer). However, the screen is roughly divided into four parts, top, bottom, left, and right, and driven by four selection lines and voltage supply line drivers (401) arranged beside the LCD matrix (406). Further, each of the four divided screens is further divided in half and driven by a data line driver (402) provided above and below. Each driver is connected to an external circuit from a wire bonding terminal (403) by wiring (405) connected by a wire bonding method.

  For example, if attention is paid to the screen on the lower left, the number of pixels here is 1/8, 19200. If the operation of rewriting once per second is performed, the frequency of the signal sent from the wiring 405 to the data line driver 402 is 19.2 kHz. Further, the signal sent to the selection line and the voltage supply line needs to be sent to the voltage supply line with a signal of 30 Hz for at least one row, and the number of rows is 120 rows which is half of 240 rows (the other 120 rows). Because the driver on the other side is responsible), a 3.6 kHz signal is sent. In either case, the frequency is extremely small, and even if the driver is composed of an a-Si TFT, there is almost no problem.

Further, when the driver circuit is formed at the same time as the matrix in this way, a decrease in yield due to that is negligible.
In the present invention, the capacitance C between the gate electrode of Tr2 and the channel is particularly problematic. As described above, in maintaining the potential of V ₁ , the OFF resistance of Tr ₁ and C are its parameters. The OFF resistance of the TFT can be varied to some extent by changing the thickness and width of the channel. However, it is difficult to achieve a high resistance of 10 ¹³ Ω or higher. Meanwhile, C is is determined by the size of the gate electrode of Tr _2. For example, if the gate electrode is 10 × 100 μm ² and the thickness of the insulating film is 100 nm, C is 10 ⁻¹³ to 10 ⁻¹² F. If silicon nitride having a high dielectric constant is used as the insulating film, C increases.

Use of an area of 10 × 100 μm for the gate electrode of Tr ₂ is undesirable because it leads to a decrease in aperture ratio. In fact, it is not wise to divide a larger area for the TFT. Therefore, in order to solve this contradiction, it is preferable to overlap the source electrode / wiring of Tr _{1 on} the voltage supply line. In this way, a large capacity can be obtained without reducing the aperture ratio. In that case, the use of a material having a large dielectric constant for the interlayer insulator is one of the methods.

Thus, since the connection to large C to Tr _1, there may be some who are concerned about a reduction in the operating speed of the ON / OFF Tr _1. However, in the present invention, the signal of each data line is also considerably longer than the conventional selection line pulse, for example, 30 times longer. On the other hand, in the conventional TFTLCD, the capacity of the pixel electrode as a load is about 10 ⁻¹³ F. In the case of the present invention, a load capacity that is about the same as that of the prior art or about an order of magnitude larger is required. You may be able to respond and operate with

  According to the present invention, when display rewriting (including maintenance) is performed, there is a method for performing appropriate number of lines in accordance with the timing of AC conversion. For example, the method shown in FIG. For example, let's say a 100 row matrix. It is assumed that the same signal is applied to the voltage supply lines in the five rows of the first row, the 21st row, the 41st row, the 61st row, and the 81st row in synchronization. Similarly, the 5th row of the 2nd row, the 22nd row, the 42nd row, the 62nd row and the 82nd row, and the other rows also form a set and operate in synchronization with each other.

  It is assumed that the pixels from the first row to the 20th row are rewritten at the time of the first alternating operation (FIG. 5A). At this time, a pulse is applied to the selection line and a positive voltage is applied to the voltage supply line to the pixels in the first row. On the other hand, the voltage is applied to the voltage supply line for other pixels moving in synchronization with the 21st row and other first rows, but no pulse is applied to the selection line. Therefore, at this time, only the first line among the lines operating in five groups is rewritten. The same applies to the other groups, and eventually only the first to twentieth lines are rewritten at this time.

  Next, in the 21st row, it is assumed that a negative voltage is applied to the voltage supply line simultaneously with the pulse on the selection line. However, at this time, no pulse is applied to the selection line in the first row and other rows operating in synchronization. A voltage is applied to the voltage supply line as in the 21st row. The same applies to other sets of rows, and only the 21st to 40th rows are rewritten as shown in FIG.

  Thereafter, the same operation is repeated. In FIG. 5C, lines 41 to 60 are rewritten. At this time, a positive voltage is applied to the voltage supply line. In FIG. 5D, lines 61 to 80 are rewritten. At this time, a negative voltage is applied to the voltage supply line. In FIG. 5E, the 81st to 100th rows are rewritten. At this time, a positive voltage is applied to the voltage supply line.

  In this way, in FIG. 5F, the first to twentieth rows are rewritten again. At this time, the voltage applied to the voltage supply line is negative. Each pixel is rewritten once between FIGS. 5A to 5E, but the voltage of the pixel changes five times such as positive, negative, positive, negative, and positive. This is exactly what is characteristic of the present invention. That is, the rewriting cycle is longer than the AC cycle. In particular, in the present invention, the load on the driver circuit is remarkably reduced by increasing the ratio of the period to 30 times or more.

  In the present invention, the power for driving the LCD can also be reduced. In the conventional TFTLCD or STNLCD, the frequency of the signal output to each data line is (number of rows × 30) Hz. However, in the present invention, for example, when rewriting is performed only once per second, the number of lines is (number of rows × 1) Hz.

  On the other hand, in the conventional LCD, the frequency of the signal output to each selection line is 30 Hz, whereas in the present invention, it is 1 Hz. However, in the present invention, since a 30 Hz signal is output to the voltage supply line, this point is almost the same as the conventional one.

  Eventually, the power consumption can be reduced by reducing the data line signals. Further, in the conventional STNLCD, since it is an operation in the dynamic mode, it is necessary to illuminate the screen with a backlight in order to make the screen easy to see. However, in the present invention, since the operation is in the static mode, the backlight is not used. Even if it is not, good visibility can be obtained.

  According to the present invention, it is possible to provide an LCD that is comparable to an active matrix system such as a TFTLCD in terms of visibility and that can compete with the STNLCD system in terms of cost.

  The objective of this invention is providing the LCD used for the display apparatus which does not need to display a moving image. For example, it is used as an accessory for an electric device for displaying the operation method of the device or the operating state of the device. Conventionally, such applications have been extremely limited and the market has been small. Conventionally, segment-type LCDs and SETNLCDs have been used as read-only displays.

  However, the segment method has a limited display capacity. In addition, it is necessary to install a driver IC in STNLCD. Currently, the TAB method is generally used as a technology for mounting such an IC. However, it becomes technically difficult to adopt the TAB method as the pixels become smaller. In general, when one side of a pixel is 100 μm or less, the TAB method cannot be used.

  In the present invention, since the driver IC is also integrally formed, there is no such problem. However, in the conventional a-Si TFT LCD, it is difficult to configure the driver IC with the a-Si TFT due to the difficulty of its operation method. The present invention has successfully solved this problem.

  With the present invention, a completely new application of a read-only LCD is expected. For example, the present invention does not require an external IC, and thus can be extremely miniaturized. Therefore, it can be used for a card-type display device. For example, it can be used for a card-type pager, a display device for various credit cards, and the like. Although such a use is expected, it cannot be put into practical use because there is no appropriate display device or LCD. Although the market size for such purposes is small at present, it is expected to have enormous potential demand and is expected to grow into a large market.

  In the present invention, it is desirable to use a material manufactured at a low temperature of 600 ° C. or lower as the material of the TFT. In the examples, a-Si TFTs are taken up, but there is no particular problem even with compound semiconductors such as CdS and CdSe.

  Embodiments of the present invention will be described below. In practicing the present invention, a known thin film semiconductor fabrication technique may be used.

  FIG. 6 shows an example of a pixel driving circuit and a manufacturing method thereof for carrying out the present invention. This shows a state when the pixel circuit is viewed from above. The circuit of this embodiment has an inverted stagger type double TFT with triple metal wiring. In order to produce such a circuit, the following may be performed.

First, a selection line (which becomes a gate electrode / wiring of Tr ₁ ) 601 made of a metal material such as aluminum is patterned on a suitable substrate (mask 1). At this time, if a metal oxide film having good insulation is formed on the surface of the selection line by an anodic oxidation method or the like, the probability that a defect will occur in a later process is reduced. Then, a first insulating layer functioning as a gate insulating film and an interlayer insulator is formed. Next, an amorphous silicon or polysilicon film is formed by CVD or the like and patterned (mask 2). Next, using the mask 1, an etching stopper such as a silicon nitride film is formed so as to overlap the selection line. Alternatively, the etching stopper may be patterned so as to overlap the selection line in a self-aligned manner by irradiating light from the back surface of the substrate.

  Next, an impurity-doped semiconductor film is formed and patterned (mask 3). In this way, the semiconductor region 602 of the first TFT is manufactured. FIG. 6A shows this state.

  Next, the data line 603 is formed of a metal material. The data line is formed so as to be connected to one of the source and the drain of the first TFT (mask 4). At the same time, a wiring 604 extending from an electrode connected to the other of the source and the drain of the first TFT is formed using the same material. At this time, the reason why the metal wiring 604 exhibits such a complicated account is to make it overlap with the voltage supply line later. This is shown in FIG.

  Further, as in the case of manufacturing the first TFT, a second insulating film (which becomes a gate insulating film of the second TFT) is formed, and the activated semiconductor film of the second TFT is patterned (mask). 5) Next, an etching stopper is formed using the mask 4, and an impurity-doped semiconductor film is formed and patterned (mask 6). In this way, the semiconductor region 605 of the second TFT is formed. Further, a voltage supply line 606 is formed from a metal material (mask 7), and a drain and a contact of the second TFT are formed. In this way, a circuit as shown in FIG. 6C is obtained. Finally, as shown in FIG. 6D, the transparent conductive film 607 is patterned (mask 8) to complete the circuit.

  In the above steps, a total of 8 masks are required, and the mask process is required 10 times. In order to actively reduce the mask process, it is desirable to introduce a self-alignment process. In order to form a TFT without using an etching stopper, an impurity semiconductor to be a source and drain region may be first patterned and then an activated semiconductor film may be formed.

  In this circuit, the voltage supply line and the gate electrode wiring of the second TFT are designed to overlap intentionally. This is to increase the capacity of both (corresponding to C in FIG. 1A), to increase the holding time of the charge accumulated in the gate electrode of the second TFT, and to reduce the number of rewrites. Because it was intended.

An example of a circuit of a pixel of the TFTLCD of the present invention and an example of its operation are shown. A circuit example and an operation example of a pixel of a conventional TFTLCD are shown. An outline of the relationship between the number of pixels of various LCDs and cost is shown. The structural example of the panel of TFTLCD of this invention is shown. The example of the display method of TFTLCD of this invention is shown. An example of a circuit of a pixel of a TFTLCD of the present invention and an example of a manufacturing method thereof will be shown.

Explanation of symbols

401 ··· Selection line / voltage supply line driver circuit 402 ··· Data line driver circuit 403 ··· Bonding pad 405 ··· Bonding wire 406 ··· Matrix region

Claims (11)

A substrate,
An electrical device having a pixel portion having a plurality of pixels arranged in a matrix on the substrate, and a driver circuit,
Each of the plurality of pixels is
A first thin film transistor;
A second thin film transistor;
A pixel electrode connected to one of a source or a drain of the second thin film transistor;
A counter electrode facing the pixel electrode;
Have
A wiring connected to one of a source and a drain of the first thin film transistor is electrically connected to a gate electrode of the second thin film transistor;
The other of the source and the drain of the first thin film transistor is electrically connected to the data line, the gate electrode is electrically connected to the selection line,
The other of the source and the drain of the second thin film transistor is electrically connected to a voltage supply line;
The driver circuit is
Formed using a third thin film transistor;
The first, second and third thin film transistors are made of amorphous silicon or less than 600 ° C. ,
The first thin film transistor is an enhancement type thin film transistor,
An electric device characterized in that the potential of the counter electrode is 0 . A substrate,
An electrical device having a pixel portion having a plurality of pixels arranged in a matrix on the substrate, and a driver circuit,
Each of the plurality of pixels is
A first thin film transistor;
A second thin film transistor;
A pixel electrode connected to one of a source or a drain of the second thin film transistor;
A counter electrode facing the pixel electrode;
Have
A wiring connected to one of a source and a drain of the first thin film transistor is electrically connected to a gate electrode of the second thin film transistor;
The other of the source and the drain of the first thin film transistor is electrically connected to the data line, the gate electrode is electrically connected to the selection line,
The other of the source and the drain of the second thin film transistor is electrically connected to a voltage supply line;
The driver circuit is
Formed using a third thin film transistor;
The first, second and third thin film transistors are made of amorphous silicon or less than 600 ° C.,
The first thin film transistor is an enhancement type thin film transistor,
The potential of the counter electrode is 0;
Each of the first and second thin film transistors is an inverted staggered thin film transistor. A substrate,
An electrical device having a pixel portion having a plurality of pixels arranged in a matrix on the substrate, and a driver circuit,
Each of the plurality of pixels is
A first thin film transistor;
A second thin film transistor;
A pixel electrode connected to one of a source or a drain of the second thin film transistor;
A counter electrode facing the pixel electrode;
Have
A wiring connected to one of a source and a drain of the first thin film transistor is electrically connected to a gate electrode of the second thin film transistor;
The other of the source and the drain of the first thin film transistor is electrically connected to the data line, the gate electrode is electrically connected to the selection line,
The other of the source and the drain of the second thin film transistor is electrically connected to a voltage supply line;
The driver circuit is
Formed using a third thin film transistor;
The first, second and third thin film transistors are made of amorphous silicon or less than 600 ° C.,
The first thin film transistor is an enhancement type thin film transistor,
The potential of the counter electrode is 0;
An electrical apparatus wherein the gate insulating film of the second thin film transistor is a silicon nitride film. A substrate,
An electrical device having a pixel portion having a plurality of pixels arranged in a matrix on the substrate, and a driver circuit,
Each of the plurality of pixels is
A first thin film transistor;
A second thin film transistor;
A pixel electrode connected to one of a source or a drain of the second thin film transistor;
A counter electrode facing the pixel electrode;
Have
A wiring connected to one of a source and a drain of the first thin film transistor is electrically connected to a gate electrode of the second thin film transistor;
The other of the source and the drain of the first thin film transistor is electrically connected to the data line, the gate electrode is electrically connected to the selection line,
The other of the source and the drain of the second thin film transistor is electrically connected to a voltage supply line;
The driver circuit is
Formed using a third thin film transistor;
The first, second and third thin film transistors are made of amorphous silicon or less than 600 ° C.,
The first thin film transistor is an enhancement type thin film transistor,
The potential of the counter electrode is 0;
The gate insulating film of the second thin film transistor is a silicon nitride film;
Each of the first and second thin film transistors is an inverted staggered thin film transistor. A substrate,
An electrical device having a pixel portion having a plurality of pixels arranged in a matrix on the substrate, and a driver circuit,
Each of the plurality of pixels is
A first thin film transistor;
A second thin film transistor;
A pixel electrode connected to one of a source or a drain of the second thin film transistor;
A counter electrode facing the pixel electrode;
Have
A wiring connected to one of a source and a drain of the first thin film transistor is electrically connected to a gate electrode of the second thin film transistor;
The other of the source and the drain of the first thin film transistor is electrically connected to the data line, the gate electrode is electrically connected to the selection line,
The other of the source and the drain of the second thin film transistor is electrically connected to a voltage supply line;
The driver circuit is
Formed using a third thin film transistor;
The first, second and third thin film transistors are made of amorphous silicon or less than 600 ° C.,
The first thin film transistor is an enhancement type thin film transistor,
The potential of the counter electrode is 0;
The electric device, wherein a wiring connected to one of the source and the drain of the first thin film transistor and the voltage supply line overlap. A substrate,
An electrical device having a pixel portion having a plurality of pixels arranged in a matrix on the substrate, and a driver circuit,
Each of the plurality of pixels is
A first thin film transistor;
A second thin film transistor;
A pixel electrode connected to one of a source or a drain of the second thin film transistor;
A counter electrode facing the pixel electrode;
Have
A wiring connected to one of a source and a drain of the first thin film transistor is electrically connected to a gate electrode of the second thin film transistor;
The other of the source and the drain of the first thin film transistor is electrically connected to the data line, the gate electrode is electrically connected to the selection line,
The other of the source and the drain of the second thin film transistor is electrically connected to a voltage supply line;
The driver circuit is
Formed using a third thin film transistor;
The first, second and third thin film transistors are made of amorphous silicon or less than 600 ° C.,
The first thin film transistor is an enhancement type thin film transistor,
The potential of the counter electrode is 0;
The wiring connected to one of the source or drain of the first thin film transistor and the voltage supply line overlap,
Each of the first and second thin film transistors is an inverted staggered thin film transistor. In claim 5 or claim 6,
An electric device characterized in that a capacitor is formed in a region where a wiring connected to one of the source and the drain of the first thin film transistor and the voltage supply line overlap. In any one of Claims 1 thru | or 7,
The electrical apparatus is an active matrix liquid crystal display device. In any one of Claims 1 thru | or 8,
The electrical device is a card type. The electrical apparatus according to claim 9, the gas appliance electricity, which is a credit card. In claim 9,
The electrical device is a card-type pager.

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