JP4754682B2 - Display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection display device. The present invention relates to an active matrix display device, among other display devices. Typically, the present invention relates to a rear projection liquid crystal display device and a front projection liquid crystal display device.
[0002]
[Prior art]
Recently, a technique for manufacturing a semiconductor device in which a semiconductor thin film is formed on an inexpensive glass substrate, for example, a thin film transistor (TFT) has been rapidly developed. This is because the demand for active matrix liquid crystal display devices (liquid crystal panels) has increased.
[0003]
In addition, a projection type liquid crystal display device (liquid crystal projector) that enjoys an enlarged image by irradiating a pixel portion of the liquid crystal panel with intense light from a light source and irradiating the screen through a lens has been attracting attention.
[0004]
FIG. 18 shows a schematic configuration diagram of a conventional three-plate type liquid crystal projector using three liquid crystal panels. Reference numeral 8001 denotes a light source, and a white light source is used. Reference numerals 8002, 8003, 8004, and 8005 denote dichroic mirrors that reflect only light in a certain wavelength range and transmit other light. 8002 reflects only red light and transmits other light. Similarly, 8003 and 8004 reflect only blue light and transmit other light. 8005 reflects only green light and transmits other light. Reference numerals 8006 and 8007 denote total reflection mirrors. Reference numerals 8008, 8009, and 8010 denote liquid crystal panels, which display red, blue, and green images, respectively.
[0005]
[Problems to be solved by the invention]
Refer to FIG. FIG. 19 shows the principle of a three-plate projector. As shown in FIG. 19, the three-plate projector provides a color image by combining a red image, a green image, and a blue image.
[0006]
Here, as shown in FIG. 20, a case where a defective pixel exists in a liquid crystal panel 8010 (normally white) that displays a green image will be described. Note that when the defective pixel 9001 is a bright spot, the defective pixel is subjected to a process such as laser irradiation to be turned into a black spot.
[0007]
When the defective pixel 9001 exists in the liquid crystal panel 8010 that displays a green image, a defect due to the black spot is displayed in the green image. Here, it is assumed that the liquid crystal panel 8008 that displays a red image and the liquid crystal panel 8009 that displays a blue image have no defective pixels. Then, in the color image in which the three-color image is synthesized, a defect has occurred in the green image. As a result, the luminance of the pixel decreases, the red image and the blue image are synthesized, and the pixel in which the defect exists In 9002, a purplish image is displayed.
[0008]
Therefore, the image of the defective portion is conspicuous and causes deterioration of the image.
[0009]
Therefore, the present invention has been made in view of the above problems, and provides a display device that can prevent image degradation even when a display panel having defective pixels is used.
[0010]
[Means for Solving the Problems]
In the present invention, when there is a defective pixel on the display panel, the luminance of the pixel corresponding to the predetermined coordinate is increased based on the data specifying the position coordinate of the defective pixel, and the average value of luminance in the predetermined range (hereinafter referred to as average luminance) The image is displayed by performing data correction so as to be constant.
[0011]
By doing so, the deterioration due to the defective pixel becomes inconspicuous in the image of the display panel having the defective pixel, and the deterioration of the image can be prevented as much as possible.
[0012]
In addition, as means for specifying the position coordinates of the defective pixel, there are known techniques, for example, a method of specifying by captured image processing using a CCD camera or the like, a method of specifying only by a TFT substrate using an OE element and a CCD camera, and a pixel on the TFT substrate side A method for specifying the readout circuit in a mixed manner may be used.
[0013]
In the present invention, a correction table for correcting the luminance is created in advance, and the video data is corrected by the correction table during normal use.
[0014]
When the defective pixel is not a black spot but a bright spot, the above-described correction is executed after repairing with a laser or the like to make a black spot.
[0015]
Please refer to FIG. FIG. 1 shows a state in which a color image is provided by combining a red image, a green image, and a blue image in a three-plate projection display device.
[0016]
In the example shown in FIG. 1, the defective pixel 101 exists in the display panel that displays a green image. It is assumed that the defective pixel 101 is a black spot. When the defective pixel 101 is a bright spot, the defective pixel is subjected to black spot processing such as a laser so as to be black spotted. Therefore, the defect due to the black dot is displayed in the green image. Here, it is assumed that the display panel displaying a red video and the display panel displaying a blue video have no defective pixels and display a normal video. Conventionally, in a color image in which images of red, green, and blue colors are combined, defective pixels exist in the green image. As a result, the green image brightness at a certain coordinate becomes zero, and the red image and the blue image Only the video is synthesized, and the purple-colored video is displayed on the pixel 104 where the defect exists. If this is the case, the pixel 104 becomes conspicuous, and a good display cannot be obtained.
[0017]
Therefore, the present invention, as shown in FIG. 1, in the display panel that displays a red image and the display panel that displays a blue image, has the same coordinates (m, n) as the defective pixels of the display panel that displays a green image. ) Pixel luminance correction (specifically, correction for increasing the average luminance of the pixel 102 and the pixel 103). Human vision is more sensitive to light and dark sensitivity than to chromaticity sensitivity. Therefore, by increasing the brightness of the pixel having the same coordinate as that of the defective pixel, the defective pixel becomes inconspicuous in the composite image of the images of the three display panels, and deterioration of the image can be prevented as much as possible.
[0018]
Of course, an example in which a defective pixel is present in a green display panel in a projection display device using three display panels is shown here, but it is needless to say that the present invention is not limited to a green display panel.
[0019]
Here, the configuration of the present invention will be described below.
[0020]
The configuration of the invention disclosed in this specification is as follows.
In a projection type display device having three display panels, means for specifying a display panel having defective pixels among the three display panels;
Means for identifying coordinates of the defective pixel;
In the display panel other than the display panel having the defective pixel among the three display panels, the defective pixel correction system includes means for increasing the luminance of the pixel having the same coordinate as the coordinate of the defective pixel.
[0021]
In addition to the above configuration, another invention disclosed in this specification is characterized in that correction is performed to increase the luminance of a pixel adjacent to a defective pixel of a green display panel, as shown in FIG. By increasing the luminance of the pixel having the same coordinate as that of the defective pixel and increasing the luminance of the adjacent pixel, the defective pixel in the composite image of the three display panels becomes inconspicuous, and deterioration of the image can be prevented as much as possible.
[0022]
Of course, an example in which a defective pixel is present in a green display panel in a projection display device using three display panels is shown here, but it is needless to say that the present invention is not limited to a green display panel.
[0023]
Other aspects of the invention disclosed in this specification are:
In a projection type display device having three display panels, means for specifying a display panel having defective pixels among the three display panels;
Means for identifying coordinates of the defective pixel;
Means for increasing the brightness of a pixel at coordinates adjacent to the coordinates of the defective pixel;
In the display panel other than the display panel having the defective pixel among the three display panels, the defective pixel correction system includes means for increasing the luminance of the pixel having the same coordinate as the coordinate of the defective pixel.
[0024]
In addition, the configuration of another invention disclosed in this specification is as follows:
A light source;
An optical system for separating light emitted from the light source into three lights;
Three display panels including one display panel having at least one defective pixel;
An optical system for synthesizing images of the three display panels and projecting them on a screen;
A projection-type display device comprising: a defective pixel correction system that increases the luminance of a pixel having the same coordinate as the coordinate of the defective pixel in a display panel other than the display panel in which the defective pixel exists.
[0025]
In addition, other inventions disclosed in this specification are:
In a display device having one display panel having defective pixels, means for specifying the position coordinates of the defective pixels;
Means for increasing the brightness of a pixel adjacent to the defective pixel;
It is a defective pixel correction system characterized by having.
[0026]
That is, a direct-view display device using a single display panel is characterized in that correction is performed to increase the luminance of pixels adjacent to defective pixels of the display panel. By performing correction to increase the luminance of adjacent pixels, defective pixels are not noticeable in the image on the display panel, and deterioration of the image can be prevented as much as possible. This is particularly effective when the pixel size is very small.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0028]
Here, as shown in FIG. 20, it is assumed that there is one black point due to a defective pixel at the coordinates (m, n) on the green display panel. FIG. 21 shows the average luminance of each pixel at the coordinates (m, n), coordinates (m-1, n), and coordinates (m + 1, n) at this time. In this case, in the color image obtained by combining the images of red, green, and blue colors, the average luminance of green at coordinates (m, n) becomes zero as shown in FIG. 21, and the average luminance of red and the average luminance of blue Only is synthesized. As a color display, a purplish color was displayed, and the total average luminance was also lowered.
[0029]
As shown in FIG. 22 (Journal of the Television Society: No. 3, pp. 29-35, 1977), human vision has different characteristics of light and dark sensitivity and chromaticity sensitivity depending on the spatial frequency. Comparing the chromaticity sensitivity with the light / dark sensitivity, the relative sensitivity is 8: 1 (light / darkness sensitivity: chromaticity sensitivity) and the chromaticity sensitivity is lower, and the video frequency is 1/3 to 1/4 of the spatial frequency band. It has become. That is, human visual perception is superior to color perception over light perception.
[0030]
Therefore, when the display on the liquid crystal panel is viewed with the human eye, it is easy to recognize the decrease in the average luminance due to the defective pixel, and thus the defective pixel portion is conspicuous.
[0031]
Therefore, as shown in FIG. 2, the average luminance of the pixels located at the coordinates (m, n) of the display panel other than green (red or blue) is increased, and the apparent luminance is corrected to a constant value. This is a feature of the present invention.
[0032]
Although FIG. 2 shows an example in which the luminance of the pixels located at the coordinates (m, n) of the red and blue display panels is increased and the apparent luminance is constant, there is no particular limitation. For example, correction for increasing the average luminance of only the red display panel may be performed, or correction for increasing the average luminance of only the blue display panel may be performed. In addition, it is preferable that the apparent luminance is substantially constant, but a sufficient effect can be obtained even by a correction that reduces the luminance difference as compared with the conventional case (FIG. 21).
[0033]
Thus, even when a black dot due to a defective pixel exists on the display panel, the position of the defective pixel cannot be recognized by human eyes.
[0034]
In addition to the above configuration, as shown in FIGS. 3 and 4, eight coordinates (coordinates (m ± 1, n ± 1), which are located adjacent to the coordinates (m, n) of the defective pixel, A configuration may be adopted in which the average luminance of the pixels at the coordinates (m ± 1, n) and the coordinates (m, n ± 1)) is increased and the apparent luminance is corrected to be a substantially constant value. 3 and 4 show an example in which the average luminance of the eight coordinates located adjacent to the defective pixel (m, n) in the green display panel is increased, the red display panel The average brightness of the eight coordinates may be increased, the average brightness of the eight coordinates in the blue display panel may be increased, or the eight coordinates in all the display panels (red, blue, green) may be increased. The average brightness may be increased. Further, the number of pixels adjacent to the defective pixel is not limited to eight, and some of them may be used, or correction for increasing the average luminance of eight or more pixels may be performed.
[0035]
Here, the operation flow of the defective pixel correction system according to the present invention will be described with reference to the flowchart of FIG. Here, a method of creating a correction table for a defective pixel correction system before incorporating a liquid crystal panel into a display device will be described.
[0036]
First, it is confirmed whether a defective pixel exists in the liquid crystal panel. As means for confirming whether there is a defective pixel, a known technique, for example, a method of specifying by a captured image processing by a CCD camera, a method of specifying only by a TFT substrate by an OE element and a CCD camera, pixel reading to the TFT substrate side What is necessary is just to use the method etc. which specify a circuit mixedly.
[0037]
If there are no defective pixels, the process ends and the panel can be used as a normal panel without defective pixels. If a defective pixel exists, the coordinates of the defective pixel are specified. Then, it is confirmed whether the defective pixel is a black spot or a bright spot. In this specification, a black spot means a state of a pixel whose light transmittance is almost 0% (arbitrary unit) from start to finish, and a bright spot is a light transmittance of almost 100% (arbitrary unit) from start to finish. This is the state of the pixel. If the defective pixel is a bright spot, it is repaired to a black spot by a laser or the like.
[0038]
Then, the coordinates of the defective pixel are input to the defective pixel coordinate input circuit, and whether the liquid crystal panel having the defective pixel is used for displaying a red, green, or blue image is input. With this input, in the digital video data correction circuit that supplies video to a liquid crystal panel other than the liquid crystal panel with the defective pixel, correction data for increasing the luminance of the pixel having the same coordinate as the defective pixel is created and stored in the luminance correction memory. Is done.
[0039]
The above operation is repeated for all defective pixels (returning to “A”). When the creation of the correction data for all defective pixels is completed, the creation of the correction data for the liquid crystal panel is finished and the correction table is completed. Similarly, correction tables for all three liquid crystal panels incorporated in the display device are created and stored in the corresponding luminance correction memory.
[0040]
Next, the three liquid crystal panels for which the creation of the correction table has been completed are incorporated into the display device.
[0041]
Here, an example of a circuit block diagram incorporating a luminance correction memory in which the correction table is stored will be described with reference to FIG.
[0042]
Reference numerals 301, 302, and 303 denote display panels, which are liquid crystal panels having digital drivers here. 301, 302, and 303 respectively display red (R), green (G), and blue (B) images on the pixel portion. Reference numerals 301-2, 302-2, and 303-2 denote source drivers, and 301-3, 302-3, and 303-3 denote gate drivers. The liquid crystal panels 301, 302, and 303 are all liquid crystal panels having the same specifications. In addition, a liquid crystal panel other than the liquid crystal panel may be used as long as it can be used as a display panel of a projection display device.
[0043]
Digital video data is supplied from an external digital video data supply source 308 to digital video data correction circuits 304, 305, and 306. The digital video data correction circuit (R) 304 has digital video data forming a red video, the digital video data correction circuit (G) 305 has digital video data forming a green video, and the digital video data correction circuit (B) 306 is supplied with digital video data forming a blue image.
[0044]
Digital video data correction circuits 304, 305, and 306 supply digital video data to the liquid crystal panels 301, 302, and 303, respectively. The digital video data correction circuits 304, 305, and 306 each have a luminance correction memory. The digital video data correction circuit corrects the input digital video data based on the tables stored in the luminance correction memories 304-1, 305-1 and 306-1, and applies the corrected digital video data to the liquid crystal panel. Supply.
[0045]
The defective pixel coordinate input circuit 307 sends the input coordinate information of the defective pixel to the digital video data correction circuit of the liquid crystal panel without the defective pixel. Based on this coordinate information, the digital video data correction circuit creates a correction table and stores it in the luminance correction memory.
[0046]
During the operation of the display device, digital video data is input from the outside to the digital video data correction circuit, and the digital video data is converted according to the generated correction table to generate corrected digital video data. The corrected digital video data is input to the liquid crystal panel, and the liquid crystal panel displays an image based on the corrected digital video data.
[0047]
Here, a liquid crystal panel having a digital driver is shown as an example, but the present invention can also be applied to a liquid crystal panel having an analog driver. In this case, the digital video data supplied from the digital video data correction circuit is converted into analog video data by the D / A conversion circuit and then input to the liquid crystal panel.
[0048]
The defective pixel correction system can be incorporated and integrated in a display device, particularly a projection display device.
[0049]
In addition to the defective pixel correction system, image correction such as gamma correction may be performed.
[0050]
In the above configuration, an example using three panels is shown. Even when one panel is used, defective pixels are corrected by correcting the luminance of eight pixels adjacent to the defective pixels. It can be made inconspicuous. This is particularly effective when the pixel size is very small.
[0051]
The present invention having the above-described configuration will be described in more detail with the following examples.
[0052]
【Example】
[Example 1]
In this embodiment, a rear projector is shown as an example of the projection display device of the present invention. FIG. 7 shows a perspective view of the rear projector of this embodiment. Reference numeral 401 denotes a rear projector main body, 402 denotes a projection display device according to the present invention, 403 denotes a reflector, and 404 denotes a screen.
[0053]
The projection display device includes three liquid crystal panels, and includes a light source (here, a white light source), a dichroic mirror that reflects only light in a certain wavelength range and transmits other light, a total reflection mirror, and the like. Yes.
[0054]
Here, a liquid crystal panel having a digital driver was used. The liquid crystal panel includes a pixel portion that displays red (R), green (G), and blue (B) images, a source driver, a gate driver, a digital video data dividing circuit, and the like. The three liquid crystal panels are all liquid crystal panels having the same specifications.
[0055]
8-bit digital video data is supplied from an external digital video data supply source to the digital video data correction circuit. The digital video data correction circuit (R) has 8-bit digital video data forming a red image, the digital video data correction circuit (G) has 8-bit digital video data forming a green image, and the digital video data. 8-bit digital video data forming a blue image is supplied to the correction circuit (B).
[0056]
The digital video data correction circuit supplies 8-bit digital video data to each liquid crystal panel. Each digital video data correction circuit has a luminance correction memory. The digital video data correction circuit corrects the input 8-bit digital video data based on a correction table stored in the luminance correction memory, and supplies the corrected digital video data to the liquid crystal panel.
[0057]
The defective pixel coordinate input circuit sends the input coordinate information of the defective pixel to the digital video data correction circuit of the liquid crystal panel having no defective pixel. Based on this coordinate information, the digital video data correction circuit creates correction data and stores it in the luminance correction memory.
[0058]
The steps for creating the correction table are as described in the embodiment.
[0059]
By doing so, defective pixels are not noticeable in the composite image of the three display panel images, and the deterioration of the image can be prevented as much as possible. Therefore, a liquid crystal panel having a few defective pixels can be used effectively.
[0060]
[Example 2]
In the present embodiment, a three-plate projector having a configuration different from that of the first embodiment will be described.
[0061]
In FIG. 10, 701 is a light source, 702 and 703 are dichroic mirrors, 704, 705 and 706 are total reflection mirrors, 707, 708 and 709 are liquid crystal panels, 710 is a dichroic prism, and 711 is a projection lens.
[0062]
FIG. 11 is a diagram in which the optical engine shown in FIG. 10 is incorporated in a front projector. In FIG. 11, the same reference numerals are used for portions corresponding to FIG. In FIG. 11, 801 is a main body and 802 is a screen.
[0063]
[Example 3]
FIG. 12 shows a flowchart of the operation method of the defective pixel correction system according to the present invention, which is different from the first embodiment. Here, an example in which a display device in which three liquid crystal panels are already incorporated is used will be described.
[0064]
First, the display device is operated to check whether a defective pixel exists in the color image projected on the screen. If there is no defective pixel, the process is terminated, and then normal use is performed. If a defective pixel exists, the coordinates of the defective pixel are specified. Then, it is specified whether the liquid crystal panel in which the defective pixel exists is a panel that displays red, green, or blue images.
[0065]
If the liquid crystal panel in which the defective pixel exists is a red liquid crystal panel, it is confirmed whether or not the defective pixel is a black dot. If the defective pixel is a black point, the coordinates of the defective pixel are input to the defective pixel coordinate input circuit. The defective pixel coordinate input circuit sends the coordinates of the defective pixel to a digital video data correction circuit that supplies video to the green and blue liquid crystal panels. The digital video data correction circuit creates data for increasing the luminance of the pixel having the same coordinate as that of the defective pixel and stores it in the luminance correction memory.
[0066]
If the liquid crystal panel in which the defective pixel exists is a green liquid crystal panel, it is confirmed whether or not the defective pixel is a black dot. If the defective pixel is a black point, the coordinates of the defective pixel are input to the defective pixel coordinate input circuit. The defective pixel coordinate input circuit sends the coordinates of the defective pixel to a digital video data correction circuit that supplies video to the blue and red liquid crystal panels. The digital video data correction circuit creates data for increasing the luminance of the pixel having the same coordinate as that of the defective pixel and stores it in the luminance correction memory.
[0067]
When the liquid crystal panel in which the defective pixel exists is neither a red liquid crystal panel nor a green liquid crystal panel, the defective pixel exists in the blue liquid crystal panel. Also in this case, it is confirmed whether or not the defective pixel is a black dot. If the defective pixel is a black point, the coordinates of the defective pixel are input to the defective pixel coordinate input circuit. The defective pixel coordinate input circuit sends the coordinates of the defective pixel to a digital video data correction circuit that supplies video to the red and green liquid crystal panels. The digital video data correction circuit creates data for increasing the luminance of the pixel having the same coordinate as that of the defective pixel and stores it in the luminance correction memory.
[0068]
The above steps are repeated for all defective pixels (return to “A”).
[0069]
In this manner, the creation of correction data for all three liquid crystal panels incorporated in the display device is completed, and the correction table is completed.
[0070]
Thereafter, the input digital video data is converted based on a correction table stored in the luminance correction memory of the digital video data correction circuit.
[0071]
By doing so, defective pixels are not noticeable in the composite image of the three display panels, and the deterioration of the image can be prevented as much as possible. Therefore, a good display device can be provided by effectively using a liquid crystal panel having some defective pixels, and productivity is improved.
[0072]
[Example 4]
In this example, an example of a method for manufacturing a liquid crystal panel used in the present invention will be described. Here, a pixel TFT of a pixel portion and a TFT of a driving circuit (a source driver, a gate driver, a D / A conversion circuit, a digital video data time gradation processing circuit, etc.) provided around the pixel portion are manufactured over the same substrate. The method will be described in detail according to the steps. However, in order to simplify the description, a CMOS circuit, which is a basic circuit such as a shift register circuit, a buffer circuit, and a D / A conversion circuit, and an n-channel TFT are illustrated in the drive circuit.
[0073]
In FIG. 13A, a low alkali glass substrate or a quartz substrate can be used as the substrate 6001. In this example, a low alkali glass substrate was used. In this case, heat treatment may be performed in advance at a temperature lower by about 10 to 20 ° C. than the glass strain point. A base film 6002 such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film is formed on the surface of the substrate 6001 where a TFT is formed in order to prevent impurity diffusion from the substrate 6001. For example, SiH by plasma CVD method _Four , NH _Three , N ₂ A silicon oxynitride film made from O is 100 nm, similarly SiH _Four , N ₂ A silicon oxynitride film manufactured from O is stacked to a thickness of 100 nm.
[0074]
Next, a semiconductor film 6003a having an amorphous structure with a thickness of 20 to 150 nm (preferably 30 to 80 nm) is formed by a known method such as a plasma CVD method or a sputtering method. In this embodiment, an amorphous silicon film having a thickness of 55 nm is formed by plasma CVD. As the semiconductor film having an amorphous structure, there are an amorphous semiconductor film and a microcrystalline semiconductor film, and a compound semiconductor film having an amorphous structure such as an amorphous silicon germanium film may be applied. Further, since the base film 6002 and the amorphous silicon film 6003a can be formed by the same film formation method, they may be formed continuously. After the formation of the base film, it is possible to prevent contamination of the surface by not exposing it to the air atmosphere, and it is possible to reduce variations in characteristics of TFTs to be manufactured and variations in threshold voltage. (FIG. 13 (A))
[0075]
Then, a crystalline silicon film 6003b is formed from the amorphous silicon film 6003a using a known crystallization technique. For example, a laser crystallization method or a thermal crystallization method (solid phase growth method) may be applied. Here, in accordance with the technique disclosed in Japanese Patent Laid-Open No. 7-130552, the crystallization method using a catalytic element is used for crystallization. A quality silicon film 6003b was formed. Prior to the crystallization step, depending on the amount of hydrogen contained in the amorphous silicon film, heat treatment is performed at 400 to 500 ° C. for about 1 hour, and the amount of hydrogen contained is reduced to 5 atom% or less for crystallization. desirable. When the amorphous silicon film is crystallized, the rearrangement of atoms occurs and the film is densified. Therefore, the thickness of the produced crystalline silicon film is larger than the thickness of the initial amorphous silicon film (55 nm in this embodiment). Also decreased by about 1 to 15%. (Fig. 13B)
[0076]
Then, the crystalline silicon film 6003b is divided into island shapes, and island-shaped semiconductor layers 6004 to 6007 are formed. Thereafter, a mask layer 6008 made of a silicon oxide film having a thickness of 50 to 100 nm is formed by plasma CVD or sputtering. (Fig. 13 (C))
[0077]
Then, a resist mask 6009 is provided, and 1 × 10 6 for the purpose of controlling the threshold voltage over the entire surface of the island-like semiconductor layers 6005 to 6007 forming the n-channel TFT. ¹⁶ ~ 5x10 ¹⁷ atoms / cm ^Three Boron (B) was added as an impurity element imparting p-type at a moderate concentration. Boron (B) may be added by an ion doping method, or may be added simultaneously with the formation of an amorphous silicon film. Although boron (B) is not necessarily added here, the semiconductor layers 6010 to 6012 to which boron (B) is added are preferably formed in order to keep the threshold voltage of the n-channel TFT within a predetermined range. It was good. (Fig. 13D)
[0078]
In order to form the LDD region of the n-channel TFT of the driver circuit, an impurity element imparting n-type conductivity is selectively added to the island-shaped semiconductor layers 6010 and 6011. Therefore, resist masks 6013 to 6016 are formed in advance. As the impurity element imparting n-type conductivity, phosphorus (P) or arsenic (As) may be used. Here, phosphorous (PH) is added to add phosphorus (P). _Three ) Was applied. The formed impurity regions 6017 and 6018 have a phosphorus (P) concentration of 2 × 10 ¹⁶ ~ 5x10 ¹⁹ atoms / cm ^Three It may be in the range. In this specification, the concentration of an impurity element imparting n-type contained in the impurity regions 6017 to 6019 formed here is defined as (n ^- ). The impurity region 6019 is a semiconductor layer for forming a storage capacitor of the pixel portion, and phosphorus (P) is added to this region at the same concentration. (Fig. 14 (A))
[0079]
Next, the mask layer 6008 is removed with hydrofluoric acid or the like, and a step of activating the impurity element added in FIGS. 13D and 14A is performed. The activation can be performed by a heat treatment at 500 to 600 ° C. for 1 to 4 hours or a laser activation method in a nitrogen atmosphere. Moreover, you may carry out using both together. In this example, a laser activation method is used, a KrF excimer laser beam (wavelength 248 nm) is used to form a linear beam, an oscillation frequency of 5 to 50 Hz, and an energy density of 100 to 500 mJ / cm. ² As a result, the entire surface of the substrate on which the island-shaped semiconductor layer was formed was processed by scanning the linear beam with an overlap ratio of 80 to 98%. Note that there are no particular limitations on the irradiation conditions of the laser beam, and the practitioner may make an appropriate decision.
[0080]
Then, the gate insulating film 6020 is formed with an insulating film containing silicon with a thickness of 10 to 250 nm by a plasma CVD method or a sputtering method. For example, a silicon oxynitride film is formed with a thickness of 120 nm. As the gate insulating film, another insulating film containing silicon may be used as a single layer or a stacked structure. (Fig. 14B)
[0081]
Next, a first conductive layer is formed to form a gate electrode. The first conductive layer may be formed as a single layer, but may have a laminated structure such as two layers or three layers as necessary. In this example, a conductive layer (A) 6021 made of a conductive nitride metal film and a conductive layer (B) 6022 made of a metal film were laminated. The conductive layer (B) 6022 is an element selected from tantalum (Ta), titanium (Ti), molybdenum (Mo), and tungsten (W), an alloy containing the element as a main component, or an alloy film in which the elements are combined. (Typically, a Mo—W alloy film or a Mo—Ta alloy film). The conductive layer (A) 6021 is a tantalum nitride (TaN), tungsten nitride (WN), titanium nitride (TiN) film, or nitride. It is made of molybdenum (MoN). Alternatively, tungsten silicide, titanium silicide, or molybdenum silicide may be applied to the conductive layer (A) 6021 as an alternative material. In the conductive layer (B), the concentration of impurities contained in the conductive layer (B) should be reduced in order to reduce the resistance. For example, tungsten (W) was able to realize a specific resistance value of 20 μΩcm or less by setting the oxygen concentration to 30 ppm or less.
[0082]
The conductive layer (A) 6021 may be 10 to 50 nm (preferably 20 to 30 nm), and the conductive layer (B) 6022 may be 100 to 400 nm (preferably 250 to 350 nm). In this embodiment, a 30 nm thick tantalum nitride film is used for the conductive layer (A) 6021 and a 350 nm Ta film is used for the conductive layer (B) 6022, both of which are formed by sputtering. In film formation by this sputtering method, if an appropriate amount of Xe or Kr is added to the sputtering gas Ar, the internal stress of the film to be formed can be relaxed and the film can be prevented from peeling. Although not shown, it is effective to form a silicon film doped with phosphorus (P) with a thickness of about 2 to 20 nm under the conductive layer (A) 6021. This improves adhesion and prevents oxidation of the conductive film formed thereon, and at the same time, an alkali metal element contained in a trace amount in the conductive layer (A) or the conductive layer (B) diffuses into the gate insulating film 6020. Can be prevented. (Figure 14 (C))
[0083]
Next, resist masks 6023 to 6027 are formed, and the conductive layers (A) 6021 and (B) 6022 are etched together to form gate electrodes 6028 to 6031 and capacitor wirings 6032. The gate electrodes 6028 to 6031 and the capacitor wiring 6032 are integrally formed of 6028a to 6032a made of a conductive layer (A) and 6028b to 6032b made of a conductive layer (B). At this time, the gate electrodes 6029 and 6030 formed in the driver circuit are formed so as to overlap with part of the impurity regions 6017 and 6018 with the gate insulating film 6020 interposed therebetween. (Fig. 14D)
[0084]
Next, in order to form a source region and a drain region of the p-channel TFT of the driver circuit, a step of adding an impurity element imparting p-type is performed. Here, impurity regions are formed in a self-aligning manner using the gate electrode 6028 as a mask. At this time, a region where the n-channel TFT is formed is covered with a resist mask 6033. And diborane (B ₂ H ₆ An impurity region 6034 was formed by an ion doping method using). The boron (B) concentration in this region is 3 × 10 ²⁰ ~ 3x10 ^{twenty one} atoms / cm ^Three To be. In this specification, the concentration of the impurity element imparting p-type contained in the impurity region 6034 formed here (p ⁺ ). (Fig. 15 (A))
[0085]
Next, in the n-channel TFT, an impurity region functioning as a source region or a drain region was formed. Resist masks 6035 to 6037 were formed, and an impurity element imparting n-type conductivity was added to form impurity regions 6038 to 6042. This is the phosphine (PH _Three ), And the phosphorus (P) concentration in this region is 1 × 10 ²⁰ ~ 1x10 ^{twenty one} atoms / cm ^Three It was. In this specification, the concentration of the impurity element imparting n-type contained in the impurity regions 6038 to 6042 formed here is defined as (n ⁺ ). (Fig. 15 (B))
[0086]
The impurity regions 6038 to 6042 already contain phosphorus (P) or boron (B) added in the previous step, but phosphorus (P) is added at a sufficiently high concentration, so that The influence of phosphorus (P) or boron (B) added in the previous step may not be considered. Further, since the phosphorus (P) concentration added to the impurity region 6038 is 1/2 to 1/3 of the boron (B) concentration added in FIG. 15A, p-type conductivity is ensured, and TFT characteristics are obtained. It had no effect on.
[0087]
Then, an impurity addition step for imparting n-type for forming an LDD region of the n-channel TFT in the pixel portion was performed. Here, an impurity element imparting n-type in a self-aligning manner is added by an ion doping method using the gate electrode 6031 as a mask. The concentration of phosphorus (P) to be added is 1 × 10 ¹⁶ ~ 5x10 ¹⁸ atoms / cm ^Three By adding the impurity element at a concentration lower than the concentration of the impurity element added in FIGS. 14A, 15A, and 15B, substantially only impurity regions 6043 and 6044 are formed. The In this specification, the concentration of an impurity element imparting n-type contained in the impurity regions 6043 and 6044 is defined as (n ^- ). (Figure 15 (C))
[0088]
Thereafter, a heat treatment process is performed to activate the impurity element imparting n-type or p-type added at each concentration. This step can be performed by a furnace annealing method, a laser annealing method, or a rapid thermal annealing method (RTA method). Here, the activation process was performed by furnace annealing. The heat treatment is performed at 400 to 800 ° C., typically 500 to 600 ° C. in a nitrogen atmosphere having an oxygen concentration of 1 ppm or less, preferably 0.1 ppm or less. In this embodiment, heat treatment is performed at 550 ° C. for 4 hours. went. Further, in the case where a substrate 6001 having heat resistance such as a quartz substrate is used, heat treatment may be performed at 800 ° C. for 1 hour, activation of the impurity element, and impurity region to which the impurity element is added A good junction with the channel formation region could be formed.
[0089]
In this heat treatment, the conductive layers (C) 6028c to 6032c are formed to have a thickness of 5 to 80 nm from the surface of the metal films 6028b to 6032b forming the gate electrodes 6028 to 6031 and the capacitor wiring 6032. For example, when the conductive layers (B) 6028b to 6032b are tungsten (W), tungsten nitride (WN) can be formed, and when tantalum (Ta) is used, tantalum nitride (TaN) can be formed. The conductive layers (C) 6028c to 6032c can be formed in the same manner even when the gate electrodes 6028 to 6031 are exposed to a plasma atmosphere containing nitrogen using nitrogen or ammonia. Further, a heat treatment was performed at 300 to 450 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% hydrogen to perform a step of hydrogenating the island-shaped semiconductor layer. This step is a step of terminating dangling bonds in the semiconductor layer with thermally excited hydrogen. As another means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) may be performed.
[0090]
In the case where the island-shaped semiconductor layer was formed from an amorphous silicon film by a crystallization method using a catalytic element, a trace amount of the catalytic element remained in the island-shaped semiconductor layer. Of course, it is possible to complete the TFT even in such a state, but it is more preferable to remove at least the remaining catalyst element from the channel formation region. As one of means for removing the catalyst element, there is a means for utilizing the gettering action by phosphorus (P). The concentration of phosphorus (P) necessary for gettering depends on the impurity region (n ⁺ The catalytic element could be gettered from the channel formation region of the n-channel TFT and the p-channel TFT by the heat treatment in the activation process performed here. (Fig. 15D)
[0091]
When the activation and hydrogenation steps are completed, a second conductive film is formed as a gate wiring. This second conductive film includes a conductive layer (D) mainly composed of aluminum (Al) or copper (Cu), which is a low resistance material, and titanium (Ti), tantalum (Ta), tungsten (W), molybdenum. It is good to form with the conductive layer (E) which consists of (Mo). In this embodiment, an aluminum (Al) film containing 0.1 to 2% by weight of titanium (Ti) is formed as the conductive layer (D) 6045, and a titanium (Ti) film is formed as the conductive layer (E) 6046. The conductive layer (D) 6045 may be 100 to 400 nm (preferably 250 to 350 nm), and the conductive layer (E) 6046 may be 50 to 200 (preferably 100 to 150 nm). (FIG. 16 (A))
[0092]
Then, in order to form a gate wiring connected to the gate electrode, the conductive layer (E) 6046 and the conductive layer (D) 6045 were etched to form gate wirings 6047 and 6048 and a capacitor wiring 6049. The etching process starts with SiCl _Four And Cl ₂ And BCl _Three The conductive layer (E) is removed from the surface of the conductive layer (E) to the middle of the conductive layer (D) by a dry etching method using a mixed gas and then the conductive layer (D) is removed by wet etching with a phosphoric acid-based etching solution. Thus, the gate wiring can be formed while maintaining the selective processability with the base.
[0093]
The first interlayer insulating film 6050 is formed of a silicon oxide film or a silicon oxynitride film with a thickness of 500 to 1500 nm, and then a contact hole reaching the source region or the drain region formed in each island-shaped semiconductor layer is formed. Then, source wirings 6051 to 6054 and drain wirings 6055 to 6058 are formed. Although not shown, in this embodiment, this electrode is a laminated film having a three-layer structure in which a Ti film is 100 nm, an aluminum film containing Ti is 300 nm, and a Ti film is 150 nm continuously formed by sputtering.
[0094]
Next, a silicon nitride film, a silicon oxide film, or a silicon nitride oxide film is formed as the passivation film 6059 with a thickness of 50 to 500 nm (typically 100 to 300 nm). When the hydrogenation treatment was performed in this state, favorable results were obtained with respect to the improvement of TFT characteristics. For example, heat treatment may be performed at 300 to 450 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% hydrogen, or the same effect can be obtained by using a plasma hydrogenation method. Note that an opening may be formed in the passivation film 6059 at a position where a contact hole for connecting the pixel electrode and the drain wiring is formed later. (Fig. 16 (C))
[0095]
Thereafter, a second interlayer insulating film 6060 made of an organic resin is formed to a thickness of 1.0 to 1.5 μm. As the organic resin, polyimide, acrylic, polyamide, polyimide amide, BCB (benzocyclobutene), or the like can be used. Here, it was formed by baking at 300 ° C. using a type of polyimide that is thermally polymerized after being applied to the substrate. Then, a contact hole reaching the drain wiring 6058 is formed in the second interlayer insulating film 6060, and pixel electrodes 6061 and 6062 are formed. The pixel electrode may be a transparent conductive film in the case of a transmissive liquid crystal display device, and may be a metal film in the case of a reflective liquid crystal display device. In this embodiment, an indium tin oxide (ITO) film having a thickness of 100 nm is formed by sputtering to form a transmissive liquid crystal display device. (Fig. 17)
[0096]
In this way, a substrate having the TFT of the driving circuit and the pixel TFT of the pixel portion on the same substrate was completed. A p-channel TFT 6101, a first n-channel TFT 6102, and a second n-channel TFT 6103 are formed in the driver circuit, and a pixel TFT 6104 and a storage capacitor 6105 are formed in the pixel portion. In this specification, such a substrate is referred to as an active matrix substrate for convenience.
[0097]
The p-channel TFT 6101 of the driver circuit includes a channel formation region 6106, source regions 6107a and 6107b, and drain regions 6108a and 6108b in an island-shaped semiconductor layer 6004. In the first n-channel TFT 6102, an LDD region 6110 that overlaps the island-shaped semiconductor layer 6005 with the channel formation region 6109 and the gate electrode 6029 (hereinafter, such an LDD region is referred to as Lov), a source region 6111, and a drain region 6112. have. The length of the Lov region in the channel length direction is 0.5 to 3.0 μm, preferably 1.0 to 1.5 μm. The second n-channel TFT 6103 has a channel formation region 6113, LDD regions 6114 and 6115, a source region 6116, and a drain region 6117 in the island-shaped semiconductor layer 6006. The LDD region is formed with an LDD region that does not overlap the Lov region and the gate electrode 6030 (hereinafter, such LDD region is referred to as Loff), and the length of the Loff region in the channel length direction is 0.3-2. It is 0 μm, preferably 0.5 to 1.5 μm. The pixel TFT 6104 has channel formation regions 6118 and 6119, Loff regions 6120 to 6123, and source or drain regions 6124 to 6126 in an island-shaped semiconductor layer 6007. The length of the Loff region in the channel length direction is 0.5 to 3.0 μm, preferably 1.5 to 2.5 μm. Further, the storage capacitor 6105 includes capacitor wirings 6032 and 6049, an insulating film made of the same material as the gate insulating film, and a semiconductor layer 6127 which is connected to the drain region 6126 of the pixel TFT 6104 and to which an impurity element imparting n-type conductivity is added. Is formed. Although the pixel TFT 6104 has a double gate structure in FIG. 17, it may have a single gate structure or a multi-gate structure in which a plurality of gate electrodes are provided.
[0098]
Next, using a known method, the substrate 6067 on which the counter electrode 6068 and the alignment film 6069 are formed and the active matrix substrate are bonded to each other with a sealant (not shown). Thereafter, liquid crystal 6070 is injected and sealed with a sealant (not shown). In this embodiment, display is realized in a twisted nematic mode (TN mode) using a nematic liquid crystal.
[0099]
Thus, the liquid crystal panel of this example is completed.
[0100]
As described above, in this embodiment, the structure of the TFT constituting each circuit is optimized according to the specifications required by the pixel TFT and the drive circuit, and the operation performance and reliability of the semiconductor device are improved. Furthermore, the LDD region, the source region, and the drain region can be easily activated by forming the gate electrode from a heat-resistant conductive material, and the wiring resistance can be sufficiently reduced by forming the gate electrode from a low-resistance material. Therefore, the present invention can be applied to a display device having a pixel portion (screen size) of 4 inches class or more.
[0101]
The liquid crystal panel completed in this embodiment can be used in any one of Embodiments 1 to 3.
[0102]
[Example 5]
In Embodiment 1, an example of a display device using three display panels is shown, but in this embodiment, an example of a display device using one display panel is shown.
[0103]
It is assumed that a defective pixel exists at the position of coordinates (m, n) in one display panel.
[0104]
In this embodiment, the average luminance of the pixels at coordinates (m ± 1, n ± 1) located adjacent to the coordinates (m, n) of the defective pixel is increased, and the apparent luminance becomes a substantially constant value. Correct as follows. In addition to the coordinates (m ± 1, n ± 1) located adjacent to the defective pixel, the average luminance at the pixels located at the coordinates (m ± 2, n ± 2) may be increased. .
[0105]
In this way, by correcting the luminance of the pixels adjacent to the defective pixels, it is possible to make the human eyes hardly recognize the defective pixels existing in the display panel. In this embodiment, it is particularly effective when the pixel size is very small.
[0106]
【The invention's effect】
Conventionally, only a few defective pixels are regarded as display defects. In addition, since it is minute and has high definition, it is very difficult to manufacture a display panel having no defective pixels, and the yield is very low.
[0107]
However, even with a display panel having defective pixels according to the present invention, a display level equivalent to that of a display panel having no defective pixels can be realized. Therefore, the product yield can be significantly improved without changing the manufacturing process.
[0108]
For example, in the case of a 60-inch rear projector, the image quality degradation level seen at 3H (2.2 m) can be equivalent to the image quality degradation level seen at 4H (3 m) by using the present invention.
[0109]
Further, even in the case of a direct-view panel display device, an image with little image quality deterioration can be obtained even when viewed at a very short distance.
[0110]
[Brief description of the drawings]
FIG. 1 is a diagram showing the concept of the present invention.
FIG. 2 is a schematic diagram showing the concept of the present invention.
FIG. 3 is a diagram showing the concept of the present invention.
FIG. 4 is a schematic diagram showing the concept of the present invention.
FIG. 5 is a flowchart for creating a correction table of the defective pixel correction system according to the present invention.
FIG. 6 is a circuit block diagram of an embodiment of a projection display device of the present invention.
FIG. 7 is a diagram illustrating an appearance of a rear projector.
FIG. 8 is a circuit block diagram of the projection display apparatus according to the first embodiment.
9 is a circuit block diagram of a liquid crystal panel of Example 1. FIG.
FIG. 10 is a diagram showing a configuration of a projection display device of the present invention.
FIG. 11 is a diagram showing an external appearance of a projection display device of the present invention.
FIG. 12 is a flowchart for creating a correction table of the defective pixel correction system according to the third embodiment.
FIG. 13 is a diagram illustrating a manufacturing process of an AM-LCD.
FIG. 14 is a diagram illustrating a manufacturing process of an AM-LCD.
FIG. 15 is a diagram illustrating a manufacturing process of an AM-LCD.
FIG. 16 is a diagram illustrating a manufacturing process of an AM-LCD.
FIG. 17 is a cross-sectional structure diagram of an active matrix liquid crystal display device.
FIG. 18 is a configuration example of a three-plate projection display device.
FIG. 19 is a diagram illustrating a state in which a color image is formed by combining three images.
FIG. 20 is a diagram illustrating a state in which a color image is formed when there is one defective pixel in one display panel. (Conventional example)
FIG. 21 is a schematic diagram illustrating a state in which a color image is formed when there is one defective pixel in one display panel. (Conventional example)
FIG. 22 is a diagram illustrating an example of spatial frequency characteristics of chromaticity and brightness.

Claims (5)

A projection type display device having three display panels,
Means for identifying the coordinates of a defective pixel that is a black spot ;
Means for identifying a display panel having the defective pixel among the three display panels;
Luminance of an image synthesized by the three display panels at a pixel having the same coordinates as the defective pixel, and Luminance of an image synthesized by the three display panels at a pixel having the same coordinates as a pixel adjacent to the defective pixel Among the pixels of the display panel having the defective pixel, the luminance of the pixel adjacent to the defective pixel, and the pixel of the display panel other than the display panel having the defective pixel. And a means for correcting the coordinates of the defective pixel and the luminance of the pixel having the same coordinate. A projection type display device having three display panels,
Means for identifying the coordinates of the defective pixel;
Means for identifying a display panel having the defective pixel among the three display panels;
Means for determining whether the defective pixel is a black spot or a bright spot;
Means for repairing the defective pixel determined as a bright spot by the means for determining to a black spot;
Luminance of an image synthesized by the three display panels at a pixel having the same coordinates as the defective pixel, and Luminance of an image synthesized by the three display panels at a pixel having the same coordinates as a pixel adjacent to the defective pixel Among the pixels of the display panel having the defective pixel, the defective pixel that has been determined to be a black point by the means for determining or the defective pixel that has been repaired to a black point by the means for repair Means for correcting the luminance of a pixel adjacent to the pixel and the luminance of a pixel having the same coordinates as the coordinates of the defective pixel among the pixels of a display panel other than the display panel having the defective pixel. Projection type display device. In claim 2,
The said repair is performed by laser irradiation, The projection type display apparatus characterized by the above-mentioned. In any one of Claims 1 thru | or 3,
The projection type display device, wherein the display panel is an active matrix type display panel. In any one of Claims 1 thru | or 4,
The projection display device, wherein the display panel is a liquid crystal panel.

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