The present invention relates to a photodiode, a photodiode-equipped display device and a fabrication method for the same. More particularly, the present invention relates to a photodiode preferably used for a liquid crystal display device having a plurality of active elements and driven by the active elements, a display device equipped with the photodiode, a method for fabricating the photodiode, and a method of making a display device equipped with the photodiode.
Liquid crystal display devices are used in a wide variety of equipment. Devices utilizing photodiodes are increasingly diversified, and so is the environment in which the liquid crystal display devices are used. Superior operability under versatile environment as well as energy-saving features are strongly in demand. Liquid crystal display devices themselves offer an increasing range of functions nowadays, expanding their application field.
An example of a multi-functional liquid crystal display device as disclosed in Patent Document 1 can capture images. The display device disclosed in Patent Document 1 is a display device having, on the image element array substrate constituting a liquid crystal display device, an optical sensor that can capture images.
Display devices having the image-capturing capability directly incorporate, on the image element array substrate constituting a liquid crystal display device, an optical sensor that can capture images. The charge of a capacitor connected to the optical sensor is designed to change according to the amount of light received by the optical sensor. Images are captured by detecting the voltages across the capacitor.
This optical sensor is composed of, for example, a photodiode. In the formation process of active elements such as TFTs for driving pixels of a display device, the photodiode can be formed at the same time. The photodiode therefore can be disposed with ease in each individual pixel.
In liquid crystal display devices, the display quality depends heavily on the operation environment, in particular, the ambient brightness (external light) of the site where the display is used. The display luminance is therefore adjusted according to the ambient brightness. For ambient brightness detection, optical sensors are employed in display devices. In the case of liquid crystal display devices, photodiodes as optical sensors are readily formed on the active element substrate together with active elements such as TFTs in the same formation process.
On the substrate 41, data drivers 43 and gate drivers 44 are formed in the area peripheral to the display region. The active elements disposed on the display region are connected to the data drivers or the gate drivers via data lines or gate lines (both not shown), respectively. Furthermore, a plurality of photodiodes 45 are disposed in the area peripheral to the display region of the substrate 41.
In
The p-type semiconductor region 61 and n-type semiconductor region 63 of the photodiode 60 are connected to source wiring films 58 through wirings 57 provided in the contact holes disposed through a gate insulating film 54, interlayer insulating film 55 and planarizing layer 56. This configuration makes the source wiring films 58 the external lead-out terminals. “59” denotes a protective film. “52” is a light shielding film made of a metal or the like, which is employed to shield light from the bottom in
The gate insulating film 54 is a layer that insulates the gate electrode of the TFT formed simultaneously with the photodiode 60. In
Similarly, source wiring film 58 is formed of a metal or other conductive film utilized as source wiring in TFT fabricated simultaneously with the photodiode 60. The source wiring film 58 is so named due to this fabrication process.
The output properties of the photodiode 60 shown in
The photodiode shown in
In
The precision of the i-type semiconductor region 62 formed in this manner depends on the etching precision for the metal wirings 67 and 68. The channel length, therefore, depends on the formation precision of the metal wirings 67 and 68. As described above, the etching precision of the metal wirings 67 and 68 is higher than the resist pattern alignment precision. Etching therefore provides a higher precision in the channel length.
A high precision of channel length of a photodiode can be achieved according to the technology disclosed in
The present invention was devised in consideration of the issues of the conventional technology discussed above. The present invention is aimed at: providing a photodiode that has minimum variation in the channel length that contributes to the photodiode properties in which the reduction in channel length is suppressed and the reduction in aperture ratio is minimized; providing a display device equipped with the aforementioned photodiode; providing a manufacturing method for the aforementioned photodiode; and providing a manufacturing method for a display device equipped with the aforementioned photodiode.
To solve the aforementioned issues, a photodiode according to the present invention is composed of a semiconductor film having a p-type semiconductor region, an i-type semiconductor region, and an n-type semiconductor region, which regions are sequentially formed on a substrate in a planar direction of the substrate, wherein the p-type semiconductor region and the n-type semiconductor region of the photodiode are connected to wiring films formed over an interlayer insulating film formed over the photodiode, via wirings provided through the interlayer insulating film, and the wiring films, which are formed over the interlayer insulating film, cover the p-type semiconductor region and the n-type semiconductor region, reach edges of an i-type semiconductor region, and determine a channel length contributing to properties of the photodiode.
According to this aspect, the wiring films are formed over the interlayer insulating film by etching with a high alignment precision. That is, since the photodiode channel length is determined by the wiring films formed by the high-precision etching, photodiodes having properties as designed, and multiple photodiodes having minimum variation in properties can easily be obtained. Also, the reduction in channel length can be suppressed, and the reduction in the aperture ratio can be minimized.
To solve the aforementioned issues, the display device equipped with the photodiode according to the present invention is a display device having a substrate on which active elements for display are formed and a photodiode formed on the substrate, wherein the photodiode is the photodiode according to claim 1.
According to this aspect, there is provided a display device equipped with a photodiode having superior properties that is formed on the same substrate with the active elements for display. This, in the case of a display device equipped with a number of photodiodes, suppresses the variation in photodiode properties.
To solve the aforementioned issues, in a display device equipped with another photodiode according to the present invention, the active elements are TFTs, and the wiring film formed over said interlayer insulating film is the same as a source wiring layer formed at the time of a TFT source wiring layer formation.
According to this aspect, the photodiode can be formed simultaneously with TFTs, which makes the manufacturing of the entire display device very simple.
To solve the aforementioned issues, in a display device equipped with another photodiode according to the present invention, the photodiode is for detecting ambient light and adjusts a display device luminance according to a brightness of the ambient light.
According to this aspect, upon detection of the ambient brightness of the site where the display device is used, the display device can display with a luminance corresponding to the ambient brightness. This feature allows optimum displays both indoors and outdoors, and also saves energy by avoiding higher than necessary display luminance.
To solve the aforementioned issues, in a display device equipped with another photodiode according to the present invention, the photodiode is disposed in the proximity of a pixel in a display region, and can be used for image capturing or for a touch panel.
According to this aspect, a plurality of photodiodes having consistent properties can be disposed in a display region that can be relatively large. This arrangement allows high-quality image capturing without any reading irregularities. A touch panel utilizing such photodiode can provide a high-quality, stable touch detection.
To solve the aforementioned issues, the fabrication method of the photodiode according to the present invention is a fabrication method for a photodiode made of a silicon film, having a p-type semiconductor region, an i-type semiconductor region, and an n-type semiconductor region, which regions are formed in a planar direction of a substrate, and is composed of the steps of: forming, on the substrate, the silicon film which is destined to become the photodiode; forming, on the silicon film, the p-type semiconductor region, the i-type semiconductor region, and the n-type semiconductor region to form the photodiode; forming an interlayer insulating film on the photodiode; and connecting the p-type semiconductor region and the n-type semiconductor region of the photodiode to the wiring film formed on the interlayer insulating film, wherein the wiring films are formed by etching, separately cover the p-type semiconductor region and the n-type semiconductor region, extend over edges of an i-type semiconductor region while sandwiching an interlayer insulating film inbetween, and determine a channel length of the photodiode.
According to this aspect, the wiring films can be formed over the interlayer insulating film by etching with a high alignment precision. That is, since the photodiode channel length is determined by the wiring films formed by the high-precision etching, photodiodes having properties as designed and multiple photodiodes having minimum variation in properties can easily be obtained. Also, the reduction in channel length can be suppressed, and the reduction in the aperture ratio can be minimized.
To solve the aforementioned issues, in the fabrication method for the display device equipped with the photodiode according to the present invention, active elements for display are fabricated simultaneously with the photodiode in the photodiode fabrication process.
According to this aspect, the photodiode can easily be formed simultaneously with active elements of display device, which makes the manufacturing of the entire display device very simple.
To solve the aforementioned issues, in the fabrication method for the photodiode-equipped display device of the present invention, the active elements are TFTs, and the wiring films are formed simultaneously with a source wiring layer for the active elements.
According to this aspect, photodiodes can easily be formed simultaneously with the TFTs of the display device, which makes the manufacturing of the entire display device very simple. Most fabrication processes for TFTs can be used for the photodiodes as well, eliminating the need for special processes for photodiodes. This helps keep the manufacturing cost of photodiode-equipped display devices low.
As described above, in an aspect of the present invention, the photodiode is made of a semiconductor film having a p-type semiconductor region, an i-type semiconductor region and an n-type semiconductor region, which regions are sequentially formed on a substrate in the planar direction of the substrate, wherein the p-type semiconductor region and the n-type semiconductor region of the photodiode are connected to wiring films formed over an interlayer insulating film formed over the photodiode, via the wirings provided through the interlayer insulating film; the wiring films formed over the interlayer insulating film cover the p-type semiconductor region and the n-type semiconductor region of the photodiode, reach the edges of i-type semiconductor region, and determine a channel length contributing to the photodiode properties.
Another aspect of the present invention is a fabrication method of the photodiode made of a silicon film having a p-type semiconductor region, an i-type semiconductor region, and an n-type semiconductor region, which regions are disposed in the planar direction of a substrate, and is composed of the steps of: forming, on the substrate, the silicon film which is destined to become the photodiode; forming, on the silicon film, the p-type semiconductor region, the i-type semiconductor region, and the n-type semiconductor region to form the photodiode; forming an interlayer insulating film on the photodiode; and connecting the p-type semiconductor region and the n-type semiconductor region of the photodiode to the wiring film formed on the interlayer insulating film, wherein the wiring films are formed by etching, separately cover the p-type semiconductor region and the n-type semiconductor region, extend over edges of an i-type semiconductor region while sandwiching an interlayer insulating film inbetween, and determine a channel length of the photodiode.
Accordingly, there provided is a photodiode that: has a channel width, which contributes to the photodiode properties, as designed; is capable of reducing the variations in the properties of photodiodes in the case that a number of photodiodes are formed; is capable of suppressing the channel length from being shortened; and is capable of minimizing the aperture ratio reduction. Also, a display device equipped with such photodiode, and the fabrication method of the same can be provided.
Other objects of the present invention, features, and distinguished attributes will be obvious from the description below. The advantages of the present invention will be clearly understood by the following description with reference to the figures attached.
Embodiments of the present invention are described below. The description below includes various limitations preferred for carrying out the present invention. However, the scope of the present invention is not limited to the embodiments and figures below.
In
The p-type semiconductor region 11 and n-type semiconductor region 13 of the photodiode 10 are connected to source wiring films (wiring films) 8 via wirings 7 provided in the contact holes formed in a gate insulating film 4, an interlayer insulating film 5 and a planarizing layer 6. The source wiring film 8 serves as a lead-out electrode for driving the photodiode 10. As mentioned in the description of the conventional technology with reference to
As shown in
The amount that the edges 16 and 17 of the source wiring films 8 extend into the i-type semiconductor region 12 depends on the alignment precision of photo etching. The smallest possible extending amount that is more than the alignment precision is preferred, which is, in practice, approximately 0.5 μm. The channel length “L” is approximately 5 μm.
As described later, the source wiring film 8 is formed by photo etching. The alignment precision of the photo etching is higher than the precision achievable by the mask formed by the resist pattern alone. As discussed above, the channel length “L” of the photodiode 10 depends on the precision of the source wiring film 8 formed by photo etching. Therefore, compared to the conventional technology shown in
As already described, the metal wirings 67 and 68 are disposed in the technology illustrated in
The photodiode 10 can also be used for the ambient light detection of a display device, so that the display device brightness can be adjusted according to the ambient brightness. According to this, upon the detection of the ambient brightness of the site where the display device is used, the display device displays with a luminance corresponding to the ambient brightness. This feature allows for optimum displays both indoors and outdoors, and also saves energy by avoiding higher than necessary display luminance.
The photodiode 10 can also be disposed outside the display region of a display device. According to this, ambient light of the site where the display device is used can be detected outside but very close to the display region of the display device. As a result, the display device displays with a luminance corresponding to the ambient brightness. This feature allows for optimum displays both indoors and outdoors, and also saves energy by avoiding higher than necessary display luminance. In this case, the photodiode 10 does not have to be formed in the display region, which allows for a higher density of display elements in the display region and a higher aperture ratio of the display device.
The photodiode 10 can also be disposed in the display region of a display device, in proximity to each pixel. This arrangement can provide a display device equipped with photodiode 10 for image capturing or for touch detection for a touch panel. According to this, a plurality of photodiodes 10 having consistent properties allow for high-quality image capturing and allow for capturing without any reading irregularities. A touch panel utilizing such photodiode can provide a high-quality, stable detection of touch by, for example, fingers, and allows accurate tracing of complex touch movement.
Here, photodiode 10 may be formed in the proximity of each individual pixel, or one photodiode 10 may be formed for a plurality of pixels. Furthermore, a display device may be segmented, in which, for example, only display pixels are formed for the upper half of a display device, and one photodiode 10 is formed in the proximity of each display pixel for the lower half of the display device. Needless to say, also in this case, one photodiode 10 may be formed for a plurality of pixels.
In
First, a light shielding film is deposited on one side of a glass substrate 1, which is a base member, by CVD (Chemical Vapor Deposition) or sputtering. The light shielding film may be made of an insulating material such as Si, or may be a metal film having main components such as tantalum (Ta), titanium (Ti), tungsten (W), molybdenum (Mo) and aluminum (Al). The film should have a thickness of, for example, 50 nm or more. Next, a resist pattern is developed by photolithography on the silicon film, of which the photodiode 10 will be formed, over the region that overlaps the light-shielding film formation region. Then, using the resist pattern as a mask, the insulating film or the metal film is etched to provide a light-shielding film 2. The light shielding film 2 is required when a backlight is disposed at the bottom as in
Next, a base coat insulating film 3 is applied to cover the light shielding film 2. The base coat insulating film 3 can be deposited, for example, by CVD, in which a silicon oxide film or silicon nitride film is formed. The base coat insulating film 3 may be mono-layered or multi-layered. The thickness is set to, for example, 100 nm to 500 nm.
Then, silicon film 20, of which a photodiode will be made, is formed on the base coat insulating film 3 by CVD or other method. The silicon film 20 is formed of continuous grain crystal silicon or low temperature polysilicon. For example, a low temperature polysilicon film is formed in the following manner. First, silicon oxide film and amorphous silicon film are deposited sequentially over the base coat insulating film 3. Next, amorphous silicon film is laser-annealed to facilitate crystallization, to provide a silicon film 20 made of low temperature polysilicon.
In this embodiment, the silicon film 20 made of the low temperature polysilicon can also be used as a silicon film of which active element TFTs (not shown) are formed. In other words, the silicon film 20 can be deposited in the deposition process for the silicon film of which TFTs are formed.
Next, the silicon film 20 is patterned.
Next, on the patterned silicon film 21, gate insulating film 4, which is going to be an interlayer insulating film, is formed.
Next, to adjust the dosage of the patterned silicon film 21, a p-type impurity such as boron (B) and indium (In) are used for ion implantation at, for example, an implantation energy of 10 KeV to 80 KeV, and a dose of 5×1014 to 2×1016 ions. After the implantation, the impurity concentration is preferably 1.5×1020 to 3×1021 ions per cm3. This provides silicon film 22 shown in
Next, as shown in
Next, ion implantation to form an n-type diffusion layer is conducted.
After the ion implantation, as shown in
Next, as shown in
The display device equipped with photodiode 10 of the present invention may be, but not limited to, for example, a liquid crystal display device or an EL (Electro Luminescence) display device, and may be one of other types of display devices.
The display device may be, for example, a personal digital assistant (PDA) or a portable phone unit.
In figures in the description above, only the area in the proximity of the photodiode 10 is shown. However, it is apparent that the fabrication can be done simultaneously with TFTs as active elements in the display region, in the same formation process. It is also apparent that the photodiode 10 can be formed for each individual pixel.
The present invention is not limited to the embodiments described below. Those skilled in the art can modify the present invention within the scope defined by the appended claims. That is, a new embodiment may be obtained by combining the technological means that were modified as appropriate within the scope defined by the appended claims.
The specific embodiments or examples described in the detailed explanation of the present invention are merely for an illustration of the technical contents of the present invention. The present invention shall not be narrowly interpreted by being limited to such specific examples. Various changes can be made within the spirit of the present invention and the scope as defined by the appended claims.
The present invention provides a display device equipped with a photodiode as an optical sensor, which photodiode may also be utilized for a touch panel. Display devices that the present invention may be applied to are not limited to liquid crystal display devices, but include various display devices such as EL display devices. Display devices equipped with such photodiodes are in use in a number of fields, which indicates a high industrial applicability of the present invention.
Number | Date | Country | Kind |
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2008-262746 | Oct 2008 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2009/060550 | 6/9/2009 | WO | 00 | 4/5/2011 |