JP4439852B2 - Contact type area sensor - Google Patents

Description

  The present invention relates to a contact area sensor having an image sensor function. In particular, the present invention relates to a contact area sensor including a plurality of thin film transistors (TFTs) arranged in a matrix.

  In recent years, a solid-state imaging device having a photoelectric conversion element such as a CCD that reads an image signal from an optical signal such as text / graphics information on paper or video information has come to be used. This solid-state imaging device is used as a scanner, a digital camera, or the like.

  Solid-state imaging devices using a CCD as a photoelectric conversion element include a so-called line sensor and an area sensor.

  FIG. 4A shows a schematic diagram of a conventional solid-state imaging device using a line sensor having a CCD as a photoelectric conversion element. A light source 401, a line sensor 402, and a subject 403 are provided as shown in the figure.

  The light source 401 and the line sensor 402 are scanned on the subject 403 at the same speed in the scanning direction. The light emitted from the light source 401 is reflected on the subject 403, and the reflected light is read by the line sensor 402 and converted into an image signal.

  FIG. 4B shows a schematic diagram of the line sensor 402. The line sensor 402 includes a CCD 404 and an optical system 405. The CCD 404 is composed of a plurality of small CCDs (multichips). The light incident on the line sensor 402 is focused by the optical system 405 and incident on the CCD 404. The light incident on the CCD 404 is converted into an image signal as an electric signal, and an image is read.

  In the case of such a conventional solid-state imaging device in which the light receiving portion is a line sensor, it is necessary to scan the line sensor over the subject. However, when scanning with human hands, it is difficult to scan in a certain direction. When a line sensor is scanned by a machine, since a motor for scanning is provided, the solid-state imaging device itself is prevented from being reduced in size, thickness, and weight, power consumption cannot be suppressed, and vibration is weak. The problem emerges.

  In the case of such a conventional solid-state imaging device in which the light receiving portion is a line sensor, the CCD uses a silicon substrate as the substrate. Therefore, it is necessary to make light for reading the image of the subject incident between the CCD provided in the line sensor and the subject. Therefore, an optical system 405 for focusing the image to be read is required between the CCD provided in the line sensor and the subject, which is a cause of hindering the reduction in size, thickness, and weight of the solid-state imaging device itself. ing.

  On the other hand, there is a solid-state imaging device having an area sensor in which a CCD is provided as a photoelectric conversion element with respect to the line sensor. Area sensors provided with a CCD as a photoelectric conversion element are used in video cameras, digital cameras, and the like.

  When the light receiving portion is a solid-state imaging device having an area sensor, unlike the line sensor, it is not necessary to scan the subject with the light receiving portion. However, since the CCD is formed on a silicon substrate like the line sensor, it is necessary to make light for reading an image of the subject incident between the CCD provided in the area sensor and the subject. For this reason, an optical system for focusing an image to be read is required, which prevents the solid-state imaging device itself from being reduced in size, thickness, and weight.

  In addition, since the size of the silicon substrate is limited, it is difficult to form a large area sensor in the case of a CCD.

  Further, in a conventional solid-state imaging device, a color image is read by passing white light through a red, green, and blue color filter provided above each pixel of the CCD. That is, three pixels corresponding to the red, green, and blue color filters respectively read a color image as one pixel. Therefore, with this conventional method, the resolution is one third of the actual resolution. For example, in order for the area sensor to read a VGA color image (640 × 480), pixels of (640 × 3 × 480) are required. In addition, in order for the area sensor to read an SVGA color image (800 × 600), (800 × 3 × 600) pixels are required. Thus, with the conventional method, an image can be read only at a resolution of 1/3 of the actual number of pixels.

  As described above, a conventional solid-state imaging device using a CCD as a photoelectric conversion element is difficult to reduce in size, thickness, and weight, and is vulnerable to vibration.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a contact type area sensor that is small, thin, lightweight, and strong against vibration.

  In order to solve the above problems, the present invention provides a contact area sensor provided with a sensor portion having a thin film transistor (TFT) and a photodiode disposed in a matrix on a light-transmitting substrate such as glass or quartz. Form. With the above configuration, it is not necessary to provide light for reading the image of the subject between the area sensor and the subject and to provide a complicated optical system for focusing the image to be read. The sensor itself can be reduced in size, thickness, and weight.

  In addition, unlike a line sensor, a contact area sensor having thin film transistors arranged in a matrix does not need to be scanned on a subject, and the operation is simplified. There is no need to provide a motor for scanning, and the contact area sensor itself can be reduced in size, thickness, and weight, power consumption can be suppressed, and vibration can be increased.

  Also, peripheral circuits other than the contact area sensor can be formed using thin film transistors on the same substrate as the contact area sensor. As a result, the contact area sensor can be further reduced in size, thickness, and weight, and a contact area sensor with superior portability can be formed.

  In the present invention, low power consumption is realized by using an LED as a light source. In addition, by adopting the RGB light source switching method as the image reading drive method, the image reading resolution is tripled, and high-definition and high-quality images can be read.

  Furthermore, it is configured such that a large screen image can be divided and read, and the divided screen can be connected on the software. For this reason, it is possible to read a large screen larger than the area sensor can read.

  In addition, the read characters are converted into data. When the resolution of image reading is tripled, when the read characters are converted into data, the conversion into data can be performed more reliably and accurately.

  In the present invention, by forming a contact area sensor having thin film transistors (TFTs) and photodiodes arranged in a matrix, the contact area sensor itself can be reduced in size, thickness, and weight. It also saves the trouble of scanning on the subject, simplifies operation, reduces power consumption, and makes it more resistant to vibration. Peripheral circuits other than the contact area sensor are also made of thin film transistors, so that the contact area sensor can be formed on the same substrate, and the contact area sensor can be made smaller, thinner, and lighter. In addition, the power consumption can be suppressed, and a contact area sensor that is more portable can be formed.

  In the present invention, low power consumption is realized by using an LED as a light source. In addition, by adopting the RGB light source switching method as the light source driving method, the resolution of image reading is increased by a factor of three compared to the conventional configuration in which each pixel has a color filter of R, G, or B color. High-definition and high-quality images can be read. Furthermore, a contact area sensor capable of connecting split screens on software is provided, and a large screen larger than the area that can be read by the contact area sensor can be read. The read characters are converted into data. By increasing the resolution of image reading by three times by the RGB light source switching method, it is possible to make data conversion more reliable and accurate when converting the read characters into data. In addition, by forming a contact area sensor having thin film transistors (TFTs) and photodiodes, the size of the substrate can be freely set, and a large screen image can be divided and divided screens can be connected on reading software. Made it easier.

  Below, typical embodiment of this invention is shown. A schematic view seen from the side of the contact area sensor of the present invention is shown in FIG.

  FIG. 1 shows an LED 101 as a light source composed of red (R), green (G), and blue (B), a light scattering layer 102, and a contact area sensor composed of a sensor substrate 103 having light transmittance and a sensor unit 104. The subject 105 is located on the side of the sensor substrate 103 where the sensor unit 104 is provided.

  Light from any one of the R, G, and B LEDs 101 enters the light scattering layer 102. The incident light is uniformly applied to the sensor substrate 103 by the light scattering layer 102. Since the sensor substrate 103 is light transmissive, the irradiated light passes through the sensor substrate 103 and reaches the subject 105.

  Of the light reaching the subject 105, the light reflected without being absorbed by the subject 105 is incident on the sensor unit 104 provided on the sensor substrate 103, and an image signal is generated as an electrical signal.

  The operation of the sensor unit 104 provided on the sensor substrate 103 will be described with reference to FIG. A horizontal shift register 201, a vertical shift register 202, an image reading unit 207 having a plurality of sensor units 104, an analog switch 205, an image signal line 206, a signal line 208, and a scanning line 209 on the sensor substrate 103. Is provided as shown in FIG. The sensor unit 104 includes a sensor TFT 203 and a photodiode 204.

  When a gate signal is supplied from the vertical shift register 202 to the gate electrode of the sensor TFT 203 via the scanning line 209, the sensor TFT 203 is turned on, and the cathode or anode electrode of the photodiode 204 and the source region of the sensor TFT 203 are connected. Conduct.

  In this state, light reflected by the subject is incident on the photodiode 204, and data for each pixel generated by photoelectric conversion in the photodiode 204 is input as an image signal to the source region of the analog switch 205 via the signal line 208. Is done. When the gate signal from the horizontal shift register 201 is sequentially supplied to the gate electrode of the thin film transistor of the analog switch 205, the thin film transistor of the analog switch 205 is sequentially turned on, and the image signal for each pixel is sequentially transmitted from the image signal line 206. Is output.

  The image signal output from the image signal line 206 is taken into another peripheral circuit (memory, CPU, etc.).

  Next, an image reading drive system in the contact area sensor of the present invention will be described. The LED 101 as the light source in FIG. 1 emits light by the RGB light source switching method. In the image reading unit of the contact area sensor, a period until all the sensor units 104 read one image is defined as an image 1 frame period. In the RGB light source switching method, one frame period of an image is time-divided into three, and LEDs as backlights of R, G, and B are turned on in turn by 1/3 frame period (subframe period), and 1/3. An image corresponding to the color is read for each frame period (subframe period).

FIG. 3 shows a timing chart of the RGB light source switching method. In the timing chart of the RGB light source switching method in FIG. 3, the lighting timing signals (R _s , G) of the image signal writing start signal (V _sync signal), red (R), green (G) and blue (B) LEDs are shown. _S and B _S ), and an image signal (VIDEO). Tf is a frame period. T _R , T _G , and T _B are red (R), green (G), and blue (B) LED lighting periods, respectively.

One frame period (Tf) is divided into three in the time axis direction for LED lighting periods of T _R , T _G , and T _B for red (R), green (G), and blue (B), respectively.

The RGB light source switching system, LED lighting period T _R period, T _G period and T _B period, R respectively, G, LED of B is turned sequentially. During the lighting period (T _R ) of the red LED, red light is applied to the subject. The irradiated red light is reflected on the subject, enters the photodiode, is converted into an image signal R1 for one red image, and is supplied to the image signal line. Similarly, during the lighting period (T _G ) of the green LED, the subject is irradiated with green light. Then, the green light reflected on the subject is converted into an image signal G1 for one green image by the photodiode and supplied to the image signal line. Similarly, during the lighting period (T _B ) of the blue LED, the subject is similarly irradiated with blue light. Then, the blue light reflected on the subject is converted into an image signal B1 for one blue image by the photodiode and supplied to the image signal line. One frame is formed by writing these three images.

  Image reading by this RGB light source switching method can provide a resolution three times that of a conventional configuration in which each pixel is provided with a color filter of any of R, G, and B colors. In this embodiment, R, G, and B are used as the three primary colors of light, but the three primary colors of light used in the present invention are not limited to these colors.

  As described above, in the present invention, by forming a contact area sensor having thin film transistors (TFTs) and photodiodes arranged in a matrix, the contact area sensor itself can be reduced in size, thickness, and weight. It also saves the trouble of scanning on the subject, simplifies operation, reduces power consumption, and makes it more resistant to vibration.

  Peripheral circuits other than the contact area sensor can also be formed on the same substrate as the contact area sensor, making the contact area sensor more compact, thinner and lighter, and reducing power consumption. It was possible to form a contact area sensor with better portability.

  In the present invention, low power consumption is realized by using an LED as a light source.

  Furthermore, a contact area sensor capable of connecting split screens on software is provided, and a large screen larger than the area that can be read by the contact area sensor can be read.

  The read character is converted into data. When the resolution of image reading is increased by a factor of 3 compared to the conventional configuration in which each pixel is provided with a color filter of any of R, G, and B colors, It has become possible to make it more reliable and more accurate.

  Embodiments of the present invention will be described with reference to FIGS.

  In this embodiment, an example of a method for manufacturing a thin film transistor included in the contact area sensor of the present invention will be described with reference to FIGS. Here, an example in which a CMOS circuit including an n-channel TFT included in the sensor unit of the contact area sensor and an n-channel TFT and a p-channel TFT included in the drive circuit of the contact area sensor is formed over the same substrate. explain.

  As the sensor substrate 6001, a light-transmitting substrate such as a glass substrate, a plastic substrate, or a ceramic substrate can be used. Of course, it is also possible to use a quartz substrate.

  A base film 6002 made of a silicon nitride film and a base film 6003 made of a silicon oxide film are formed on the main surface of the sensor substrate 6001 where the TFT is formed. These base films are formed by plasma CVD or sputtering, and are provided to prevent impurities that change the characteristics of the TFT from the sensor substrate 6001 from diffusing into the semiconductor layer. Therefore, a base film 6002 made of a silicon nitride film is formed to a thickness of 20 to 100 nm, typically 50 nm, and a base film 6003 made of a silicon oxide film is made to have a thickness of 50 to 500 nm, typically 150 to 200 nm. What is necessary is just to form in thickness.

  Of course, the base film may be formed of only one of the base film 6002 made of a silicon nitride film or the base film 6003 made of a silicon oxide film. However, in consideration of the reliability of the TFT, a two-layer structure is used. Most desired.

  A semiconductor layer formed in contact with the base film 6003 is an amorphous semiconductor formed by a film formation method such as a plasma CVD method, a low pressure CVD method, or a sputtering method by a solid phase growth method using a laser crystallization method or a heat treatment. It is desirable to use a crystallized crystalline semiconductor. Alternatively, a microcrystalline semiconductor formed by the above film formation method can be used. Examples of the semiconductor material that can be applied here include silicon (Si), germanium (Ge), a silicon germanium alloy, and silicon carbide. In addition, a compound semiconductor material such as gallium arsenide can also be used.

  The semiconductor layer is formed with a thickness of 10 to 100 nm, typically 50 nm. The amorphous semiconductor film manufactured by the plasma CVD method contains hydrogen at a rate of 10 to 40 atom%, but a heat treatment process at 400 to 500 ° C. is performed prior to the crystallization process, It is desirable to desorb hydrogen from the film so that the hydrogen content is 5 atom% or less. Although an amorphous silicon film may be formed by other manufacturing methods such as a sputtering method or an evaporation method, it is desirable to sufficiently reduce impurity elements such as oxygen and nitrogen contained in the film.

  Further, since the base film and the amorphous semiconductor film can be formed by the same film formation method, the base film 6002, the base film 6003, and a semiconductor layer are preferably formed successively. After each film is formed, the surface can be prevented from being contaminated by not touching the air atmosphere. As a result, it is possible to eliminate one of the factors that cause TFT characteristic variations.

  A known laser crystallization technique or thermal crystallization technique may be used for the step of crystallizing the amorphous semiconductor film. A crystalline semiconductor film can also be used by a thermal crystallization technique using a catalytic element. Further, excellent TFT characteristics can be obtained by adding a gettering step to a crystalline semiconductor film formed by a thermal crystallization technique using a catalytic element to remove the catalytic element.

  On the crystalline semiconductor film thus formed, a resist mask is formed by a known patterning method using a first photomask, and the first island-shaped semiconductor layer 6004 and the second island are formed by a dry etching method. A third semiconductor layer 6005 and a third island-shaped semiconductor layer 6006 were formed.

  Next, a gate insulating film 6007 containing silicon oxide or silicon nitride as a main component is formed on the surfaces of the first island-shaped semiconductor layer 6004, the second island-shaped semiconductor layer 6005, and the third island-shaped semiconductor layer 6006. Form. The gate insulating film 6007 may be formed by a plasma CVD method or a sputtering method with a thickness of 10 to 200 nm, preferably 50 to 150 nm. (Fig. 5 (A))

  Then, the channel formation region of the first island-shaped semiconductor layer 6004, the entire surface of the second island-shaped semiconductor layer 6005, and the channel of the third island-shaped semiconductor layer 6006 are formed by the second photomask. Resist masks 6008, 6009, and 6010 were formed to cover the portions where the formation regions are to be formed.

Then, a step of forming a second impurity region was performed by adding an impurity element imparting n-type conductivity. Phosphorus (P), arsenic (As), antimony (Sb), and the like are known as impurity elements imparting n-type to crystalline semiconductor materials. Here, phosphorous is used, and phosphine (PH ₃ ) Using an ion doping method. In this step, in order to add phosphorus to the first island-like semiconductor layer 6004 and the third island-like semiconductor layer 6006 thereunder through the gate insulating film 6007, the acceleration voltage was set to be as high as 80 keV. The concentration of phosphorus added to the first island-shaped semiconductor layer 6004 and the third island-shaped semiconductor layer 6006 is preferably in the range of 1 × 10 ¹⁶ to 1 × 10 ¹⁹ atoms / cm ^3. Then, 1 × 10 ¹⁸ atoms / cm ³ was used. In this embodiment, the n-type impurity is doped after the insulating film 6007 is formed. However, before forming the insulating film 6007, resist masks 6008, 6009, and 6010 may be formed and doping may be performed. Then, regions 6011, 6012, 6013, and 6014 in which phosphorus was added to the first island-shaped semiconductor layer 6004 and the third island-shaped semiconductor layer 6006 were formed. A part of the second impurity region formed here functions as an LDD region. (Fig. 5 (B))

  Next, the resist masks 6008, 6009, and 6010 were removed. In order to remove the resist mask, an alkaline commercially available stripping solution may be used, but using an ashing method is effective. The ashing method is a method in which plasma is formed in an oxidizing atmosphere, and the hardened resist is exposed and removed. However, it is effective to add water vapor in addition to oxygen to the atmosphere.

  Then, a first conductive layer 6015 was formed on the surface of the gate insulating film 6007. The first conductive layer 6015 is formed using a conductive material whose main component is an element selected from Ta, Ti, Mo, and W. The first conductive layer 6015 may be formed with a thickness of 10 to 100 nm, preferably 150 to 400 nm. (Fig. 5 (C))

  For the first conductive layer 6015, for example, a compound such as WMo, TaN, MoTa, or WSix (x = 2.4 <X <2.7) can be used.

Conductive materials such as Ta, Ti, Mo, and W have higher resistivity than Al and Cu, but could be used without any problem up to about 100 cm ² in relation to the area of the circuit to be manufactured.

  Next, resist masks 6016, 6017, and 6018 were formed using a third photomask. The resist mask 6017 is for forming a gate electrode of a p-channel TFT, and the resist masks 6016 and 6018 are for forming a gate electrode of an n-channel TFT.

  Unnecessary portions of the first conductive layer were removed by a dry etching method, so that a first gate electrode 6019, a second gate electrode 6020, and a third gate electrode 6021 were formed. Here, in the case where a residue remains after etching, it is preferable to perform an ashing process. At this time, the first gate electrode 6019 was formed so as to overlap with part of the second impurity regions 6011 and 6012 with the gate insulating film 6007 interposed therebetween. The third gate electrode 6021 is formed so as to overlap with part of the second impurity regions 6013 and 6014 with the gate insulating film 6007 interposed therebetween. (Fig. 5 (D))

Then, the resist masks 6016, 6017, and 6018 were removed. Next, resist masks 6022 and 6023 were formed to cover the island-shaped semiconductor layers 6004 and 6006 with a fourth photomask. Then, a step of forming third impurity regions 6024 and 6025 by adding an impurity element imparting p-type conductivity to part of the second island-shaped semiconductor layer 6005 where the p-channel TFT is formed was performed. Boron (B), aluminum (Al), and gallium (Ga) are known as impurity elements imparting p-type. Here, diborane (B ₂ H ₆ ) is used with boron as the impurity element. And added by ion doping. Again, the acceleration voltage was 80 keV and boron was added to a concentration of 2 × 10 ²⁰ atoms / cm ³ . Then, as shown in FIG. 6A, third impurity regions 6024 and 6025 to which boron was added at a high concentration were formed.

  After removing the resist masks 6022 and 6023, resist masks 6029, 6030, and 6031 were formed using a fifth photomask. The resist mask 6029 was formed so as to cover the first gate electrode 6019 and to overlap with part of the second impurity regions 6011 and 6012. The resist mask 6031 was formed so as to cover the third gate electrode 6021 and to overlap with part of the second impurity regions 6013 and 6014. The resist masks 6029 and 6031 determine the offset amount of the LDD region.

  Alternatively, part of the gate insulating film 6007 may be removed using the resist masks 6029 and 6031 so that the surface of the semiconductor layer in which the first impurity region is formed is exposed. If it does in this way, the process of adding the impurity element which provides the n type implemented at the following process can be implemented effectively.

Then, a step of forming an impurity region by adding an impurity element imparting n-type was performed. Then, first impurity regions 6032 and 6035 serving as source regions and first impurity regions 6033 and 6034 serving as drain regions were formed. Here, an ion doping method using phosphine (PH ₃ ) was used. Also in this step, in order to add phosphorus to the semiconductor layer thereunder through the gate insulating film 6007, the acceleration voltage was set as high as 80 keV. The concentration of phosphorus in this region is higher than that in the step of adding the second impurity element imparting n-type, and is preferably 1 × 10 ¹⁹ to 1 × 10 ²¹ atoms / cm ^3. Then, 1 × 10 ²⁰ atoms / cm ³ was used. (Fig. 6 (B))

  Then, a first interlayer insulating film 6036 and a second interlayer insulating film 6037 were formed on the surfaces of the gate insulating film 6007 and the first, second, and third gate electrodes 6019, 6020, and 6021. The first interlayer insulating film 6036 was a silicon nitride film and was formed with a thickness of 50 nm. The second interlayer insulating film 6037 is a silicon oxide film and has a thickness of 950 nm. Further, as the second interlayer insulating film 6037, an organic resin film such as polyimide, polyamide, polyimide amide, or acrylic may be used.

  The first interlayer insulating film 6036 made of the silicon nitride film formed here is necessary for performing the next heat treatment step. This was effective in preventing the surfaces of the first, second and third gate electrodes 6019, 6020, 6021 from being oxidized.

  The heat treatment step needs to be performed to activate the impurity element imparting n-type or p-type added at each concentration. This step may be performed by a thermal annealing method using an electric heating furnace, a laser annealing method using an excimer laser, or a rapid thermal annealing method (RTA method) using a halogen lamp. However, although the laser annealing method can be activated at a low substrate heating temperature, it has been difficult to activate even the area under the gate electrode. Therefore, here, the activation process is performed by thermal annealing. The heat treatment was performed in a nitrogen atmosphere at 300 to 700 ° C., preferably 350 to 550 ° C., here 450 ° C. for 2 hours.

  In this heat treatment step, 3 to 90% of hydrogen may be added to the nitrogen atmosphere. Further, after the heat treatment step, a hydrogenation step may be performed at 150 to 500 ° C., preferably 300 to 450 ° C. for 2 to 12 hours in a 3 to 100% hydrogen atmosphere. Alternatively, hydrogen plasma treatment may be performed at a substrate temperature of 150 to 500 ° C., preferably 200 to 450 ° C. In any case, TFT characteristics can be improved by compensating for defects in which hydrogen remains in the semiconductor layer or at the interface thereof.

  After that, the first interlayer insulating film 6036 and the second interlayer insulating film 6037 are formed using a sixth photomask, a predetermined resist mask is formed, and then the source region of the TFT of the sensor portion and the TFT of the driver portion are etched. The source region and the contact hole reaching the drain region were formed. Then, a second conductive layer was formed, and source electrodes 6038, 6040, and 6042 and a drain electrode 6041 were formed by a patterning process using a seventh photomask. Although not shown, in this embodiment, this electrode was used as an electrode having a three-layer structure in which a Ti film was formed continuously by 100 nm, an Al film containing Ti having a thickness of 300 nm, and a Ti film having a thickness of 150 nm were formed by sputtering.

  A channel formation region 6045, first impurity regions 6043 and 6047, and second impurity regions 6044 and 6046 are formed in a portion that becomes an n-channel TFT in the sensor portion. Here, the second impurity regions 6044 and 6046 include regions (GOLD regions) 6044a and 6046a that overlap with the first gate electrode 6019, and regions (LDD regions) 6044b and 6046b that do not overlap with the first gate electrode 6019, respectively. Been formed. Then, the first impurity region 6043 is a source region, and the first impurity region 6047 is a drain region.

  A channel formation region 6053, first impurity regions 6051 and 6055, and second impurity regions 6052 and 6054 were formed in the n-channel TFT of the CMOS circuit of the driving unit. Here, in the second impurity region, regions (GOLD regions) 6052a and 6054a that overlap with the third gate electrode 6021 and regions (LDD regions) 6052b and 6054b that do not overlap with the third gate electrode 6021 are formed, respectively. . The first impurity region 6055 serves as a source region, and the first impurity region 6051 serves as a drain region.

  On the other hand, the channel formation region 6049 and the third impurity regions 6048 and 6050 are formed in the p-channel TFT of the CMOS circuit of the driving unit. The third impurity region 6048 serves as a source region, and the third impurity region 6050 serves as a drain region. (Fig. 6 (C))

  Next, a third interlayer insulating film 6059 was formed. The third interlayer insulating film 6059 is a silicon oxide film and has a thickness of 950 nm. Similarly to the second interlayer insulating film, an organic resin film may be used as the third interlayer insulating film 6059. Next, after a predetermined resist mask was formed using an eighth photomask, a contact hole reaching the drain region of the TFT of the sensor portion was formed by etching. Then, a third conductive layer was formed, and a drain electrode 6039 of the TFT of the sensor portion was formed by a patterning process using a ninth photomask. Although not shown, in this embodiment, this electrode was used as an electrode having a three-layer structure in which a Ti film was formed continuously by 100 nm, an Al film containing Ti having a thickness of 300 nm, and a Ti film having a thickness of 150 nm were formed by sputtering.

  Next, a metal film is formed in contact with the third interlayer insulating film 6059 and the drain electrode 6039 of the n-channel TFT in the sensor portion. A metal film is formed and patterned to form a cathode electrode 6056 of the photoelectric conversion element. In this embodiment, aluminum by sputtering is used for this metal film, but other metals can be used. For example, a laminated film made of a titanium film, an aluminum film, or a titanium film may be used.

  Next, an amorphous silicon film containing hydrogen that functions as a photoelectric conversion layer (hereinafter referred to as an a-Si: H film) is formed over the entire surface of the substrate, patterned, and subjected to photoelectric conversion layer 6057. Is made. Next, a transparent conductive film is formed on the entire surface of the substrate. In this embodiment, ITO having a thickness of 200 nm is formed as a transparent conductive film by a sputtering method. The transparent conductive film is patterned to form an anode electrode 6058 (FIG. 7A).

  Then, a fourth interlayer insulating film 6060 is formed. It is preferable to form a resin film of polyimide, polyamide, polyimide amide, acrylic, or the like as the insulating film constituting the fourth interlayer insulating film 6060 because a flat surface can be obtained. Alternatively, a stacked structure is formed, and the upper layer of the fourth interlayer insulating film 6060 is formed by forming the above resin film and the lower layer by forming a single layer or a multilayer film of an inorganic insulating material such as silicon oxide, silicon nitride, or silicon oxynitride. Also good. In this example, a 0.7 μm-thick polyimide film was formed on the entire surface of the substrate as an insulating film. Through the above steps, the contact area sensor and its driving unit as shown in FIG. 7B are completed.

  Although FIGS. 5 to 7 illustrate examples in which the sensor unit includes an n-channel TFT, the present invention may include a p-channel TFT and includes both an n-channel TFT and a p-channel TFT. You may do it. In addition, a CMOS circuit in which an n-channel TFT and a p-channel TFT are complementarily combined is shown as an example of the driving unit, but the driving unit may be an NMOS circuit using an n-channel TFT. A PMOS circuit using a p-channel TFT may be used.

  When the TFT of the sensor portion is a p-channel TFT, it is preferable that the drain electrode 6039 of the photodiode is connected to the anode electrode 6058.

  In this embodiment, the function of the contact area sensor of the present invention shown in Embodiment 1 that divides a large screen into a plurality of pieces and reads them and then combines them on software will be described with reference to FIG.

  When the contact type area sensor cannot read the screen to be read at a time, it is necessary to divide the screen to be read into a plurality of times and synthesize the read screen on the software. The screen to be read is divided into sizes that can be read by the contact area sensor. In the present embodiment, the screen to be read is divided into two, but the number of divided readings needs to be appropriately changed depending on the relationship between the contact area sensor and the size of the screen. In this embodiment, the divided screens 802a and 802b are read by the contact area sensor in two steps.

  The read divided screens 802a and 802b are synthesized on software. In the synthesis on the software, the screen 803 is obtained by automatically aligning the boundary on the software side. Even if the split screen is not automatically synthesized on the software side, the split screens 802a and 802b can be moved by a human hand, and the boundaries of the split screens 802a and 802b can be aligned while checking with the human eye.

  The combination of the divided screens on such software makes it possible to read a screen larger than the size that can be read by the contact area sensor.

  In this embodiment, the contact area sensor provided with the TFT of the present invention as a photoelectric conversion element has a function of converting a read character into data, that is, a so-called OCR function. In the present invention, the image reading resolution is compared with the conventional configuration in which each pixel is provided with a color filter of any color of R, G, or B by using the RGB light source switching method as the image reading driving method. Tripled to enable high-definition and high-quality image reading. By increasing the image reading resolution by a factor of 3, it is possible to make data conversion more reliable and accurate when converting the read characters into data.

  A portable hand scanner will be described with reference to FIG. 9 as an example of a contact area sensor provided with the TFT of the present invention as a photoelectric conversion element.

  FIG. 9A illustrates a portable hand scanner which includes a main body 901, a contact area sensor 902, an upper cover 903, an external connection port 904, and an operation switch 905. FIG. 9B is a view in which the upper cover 903 of the same portable hand scanner as in FIG. 9A is closed.

  The image data read by the contact area sensor 902 is sent from the external connection port 904 to an electronic device connected to the outside of the portable hand scanner, and the image is corrected, synthesized, edited, etc. on the software. Is possible.

Sectional drawing of the contact type area sensor of this invention. The circuit diagram of the contact type area sensor of this invention. The timing chart of the RGB light source switching system of this invention. Schematic of the line sensor which provided conventional CCD as a photoelectric conversion element. The figure which shows the preparation processes of the contact type area sensor of this invention. The figure which shows the preparation processes of the contact type area sensor of this invention. The figure which shows the preparation processes of the contact type area sensor of this invention. The figure explaining the function which synthesize | combines a split screen on software. The figure which shows an example of the portable hand scanner of this invention.

Explanation of symbols

101 LED
102 light scattering plate 103 sensor substrate 104 sensor unit 105 subject 201 horizontal shift register 202 vertical shift register 203 sensor TFT
204 Photodiode 205 Analog switch 206 Image signal line 207 Image reading unit 208 Signal line 209 Scan line

Claims (4)

A light source;
A sensor substrate in which a plurality of sensor units and drive circuits are provided on the same surface;
Have
Each of the plurality of sensor units includes a photoelectric conversion element and a thin film transistor,
The driving circuit includes a CMOS circuit including an n-channel thin film transistor and a p-channel thin film transistor,
The thin film transistor of the sensor unit is
A gate electrode;
A gate insulating film provided under the gate electrode;
Provided under the gate insulating film, a channel forming region, a pair of impurity regions A in contact with the channel forming region and overlapping the gate electrode through the gate insulating film, and a pair of impurity regions A in contact with the gate insulating film A pair of impurity regions B that do not overlap with the gate electrode via a semiconductor layer, and a semiconductor layer including a pair of impurity regions C that are in contact with the pair of impurity regions B and function as source regions or drain regions, respectively,
The p-channel thin film transistor of the driving circuit is
A gate electrode;
A gate insulating film provided under the gate electrode;
A semiconductor layer provided under the gate insulating film and including a channel formation region and a pair of impurity regions D functioning as a source region or a drain region;
The n-channel thin film transistor of the driving circuit is
A gate electrode;
A gate insulating film provided under the gate electrode;
A channel formation region, a pair of impurity regions E that are in contact with the channel formation region and overlap the gate electrode through the gate insulation film, and a pair of the impurity regions E that are respectively provided below the gate insulation film and in contact with the pair of impurity regions E And a semiconductor layer including a pair of impurity regions F that do not overlap with the gate electrode and a pair of impurity regions G that are in contact with the pair of impurity regions F and function as source regions or drain regions, respectively.
A contact area sensor. In claim 1,
The thin film transistor of the sensor unit is
A pair of first electrodes electrically connected to the pair of impurity regions C and functioning as a source electrode or a drain electrode,
The photoelectric conversion element of the sensor unit is
A second electrode that functions as one of a cathode electrode or an anode electrode;
A photoelectric conversion layer provided under the second electrode;
A third electrode provided under the photoelectric conversion layer, electrically connected to the first electrode of the thin film transistor of the sensor portion, and functioning as the other of the cathode electrode or the anode electrode; A contact area sensor. In claim 1 or claim 2,
The contact area sensor, wherein the sensor substrate transmits light from the light source and receives light reflected from a subject. In any one of Claims 1 to 3,
The contact area sensor, wherein the light source is an LED.

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