Patent Application
20110316427
The present invention relates to a photodiode, a display device provided with the photodiode and methods of manufacturing the photodiode and the display device.
Liquid crystal display devices are used in a variety of devices. As the devices installed with liquid crystal display devices become increasingly diversified, the usage environment of liquid crystal display devices widens, which creates a demand for the comfortable operability in various environments as well as a strong need for less power consumption. Additionally, liquid crystal display devices themselves are having an increasing range of functions, and the increase of the functions further widens the field of application of liquid crystal display devices.
Patent Document 1 discloses a liquid crystal display device capable of capturing images as an example of an effort for the multi-functionality. The display device disclosed in Patent Document 1 is a display device having an optical sensor capable of capturing images mounted on an image element array substrate constituting the liquid crystal display device.
This display device provided with the image capturing feature has an optical sensor capable of capturing images directly mounted on an image element array substrate constituting the liquid crystal display device and performs image capturing by changing the amount of electric charge of a capacitor connected to the optical sensor in accordance with the amount of light received at the optical sensor and detecting the voltage across the capacitor.
This optical sensor is constituted by a photodiode, for example, and can be easily formed in each pixel because this photodiode can be simultaneously formed in a step of forming an active element such as a TFT for driving a pixel electrode of the display device.
Additionally, in a liquid crystal display device, because the visibility is largely affected by an environment in which the liquid crystal display device is used, especially ambient light (outside light), the display luminance is adjusted in accordance with ambient light of a place where it is used. For this reason, display devices are installed with an optical sensor for detecting ambient light, and in a liquid crystal display device, by utilizing a step of forming TFTs and the like, a photodiode as an optical sensor can be easily formed on an active element substrate where TFTs and the like are formed in the same step.
Additionally, on the substrate 41, in regions around the display region, data drivers 43 and gate drivers 44 are formed, and the active elements provided in the display region are connected to the data drivers and the gate drivers through not-shown data wiring and gate wiring, respectively. Further, in the regions around the display region of the substrate 41, a plurality of photodiodes 45 are provided.
The p-type semiconductor region 61 and the n-type semiconductor region 63 of the photodiode 60 are connected to source wiring films 58, 58 through wiring 57, 57 in contact holes provided in a gate insulating film 54, an interlayer insulating film 55, and a planarizing layer 56, and become lead-out terminals to the outside. 59 is a protection film which also has a function as a planarizing layer. 52 is a light shielding layer made of a metal film and the like and is provided when it is desired to shield light from the bottom in
Also, here, the gate insulating film 54 is an insulating layer to insulate a gate electrode of the TFT manufactured simultaneously with the photodiode 60. In
Additionally, in a manner similar to above, the source wiring films 58, 58 are formed by utilizing a conductive film made of metal or the like that is used as source wiring and the like of the TFT manufactured simultaneously with the photodiode 60, and are therefore referred to as source wiring films due to this manufacturing origin.
In
In the art shown in
The present invention was made in view of the above-described problem of the conventional art, and it is an object of the present invention to provide a photodiode that has less changes in output characteristics even with the prolonged use, to provide a display device having the photodiode, to provide a method of manufacturing the photodiode, and to provide a method of manufacturing the display device having the photodiode.
To solve the above-described problem, a photodiode of the present invention includes at least one conductive semiconductor film for junction formation formed on a substrate, an interlayer insulating film formed on the semiconductor film, a wiring film provided on the interlayer insulating film, and a protection film covering the wiring film, wherein the protection film has been removed at least at a light receiving portion of the photodiode.
A photodiode that has less changes in output characteristics even with the prolonged use can be thereby provided.
To solve the above-described problem, a display device of the present invention is characterized in that on the substrate, in addition to the above-mentioned photodiode, a pixel electrode for display and an active element for driving the pixel electrode are formed.
A display device having a photodiode that has less characteristic changes can be thereby obtained.
To solve the above-described problem, a manufacturing method of a photodiode of the present invention is a method to manufacture a photodiode that includes at least one conductive semiconductor film for junction formation formed on a substrate, an interlayer insulating film formed on the semiconductor film, a wiring film provided on the interlayer insulating film, and a protection film covering the wiring film, the method including a step of forming a junction on the substrate, a step of forming an interlayer insulating film on the junction, a step of connecting each region forming the junction to a wiring film, a step of forming a protection film on the wiring film and the interlayer insulating film, and a step of removing the protection film from a portion corresponding to at least a light receiving portion of the photodiode.
A photodiode that has less characteristic changes with a high degree of reliability can be thereby made.
To solve the above-describe problem, another manufacturing method of a photodiode of the present invention is a method to manufacture a photodiode that includes a semiconductor film having a p-type semiconductor region, an i-type semiconductor region and an n-type semiconductor region formed on a substrate in this order along the plane direction of the substrate, an interlayer insulating film formed on the semiconductor film, a wiring film provided on the interlayer insulating film, and a protection film covering the wiring film, the method including a step of forming a silicon film on the substrate, a step of forming a main body of the photodiode by forming a p-type semiconductor region, an i-type semiconductor region, and an n-type semiconductor region on the silicon film, a step of forming an interlayer insulating film on the main body of the photodiode, a step of connecting the p-type semiconductor region and the n-type semiconductor region of the photodiode to the wiring film, a step of forming a protection film on the wiring film and the interlayer insulating film, and a step of removing the protection film from a portion corresponding to at least a light receiving portion of the photodiode.
A photodiode that has less characteristic changes with a high degree of reliability can be thereby made simultaneously with an active element of a display device such as a TFT in the same manufacturing step.
Additional objects, features, and advantages of the present invention will be sufficiently clarified by the description which follows. Also, the benefits of the present invention will become apparent from the explanation hereinafter with reference to the attached figures.
As described above, a photodiode of the invention of the present application includes at least one conductive semiconductor film for junction formation formed on a substrate, an interlayer insulating film formed on the semiconductor film, a wiring film provided on the interlayer insulating film, and a protection film covering the wiring film, wherein the protection film has been removed at least at a light receiving portion of the photodiode.
Also, a manufacturing method of a photodiode of the invention of the present application is a method to manufacture a photodiode that includes at least one conductive semiconductor film for junction formation formed on a substrate, an interlayer insulating film formed on the semiconductor film, a wiring film provided on the interlayer insulating film, and a protection film covering the wiring film, the method including a step of forming a junction on the substrate, a step of forming an interlayer insulating film on the junction, a step of connecting each region forming the junction to the wiring film, a step of forming a protection film on the wiring film and the interlayer insulating film, and a step of removing the protection film from a portion corresponding to at least a light receiving portion of the photodiode.
This makes it possible to provide a photodiode that has less changes in output characteristics even with the prolonged use. Also, this makes it possible to provide a display device provided with such a photodiode and a manufacturing method thereof.
Before embodiments of the present invention are explained, findings of the inventor of the present invention and others that led to the present invention will be described.
As previously described, when a display device having a photodiode of the conventional structure shown in
Although there are various possible causes of the entrapment of the electric charge, it appears to be caused by a generation of leak current by ITO bias or bias applied to terminals, resulting in the electric charge to be accumulated.
When the protection film (corresponding to the protection film 59 in
Hereinafter, embodiments of the present invention are described. Although various limitations preferable for embodiments of the present invention are added in the description below, the technical scope of the present invention is not limited to the embodiments or the figures hereinafter.
All of the figures are schematically drawn to clarify structures, and therefore, they do not indicate actual dimensional relations. Also, in
In
3 is a base coat insulating film, and a photodiode 10 is disposed on this base coat insulating film 3. The photodiode 10 has at least one conductive semiconductor film for junction formation. In this embodiment, the photodiode 10 includes a p-type semiconductor region 11, an i-type semiconductor region 12, and an n-type semiconductor region 13, and is configured as a lateral PIN photodiode. The p-type semiconductor region 11, the i-type semiconductor region 12, and the n-type semiconductor region 13 are formed on the substrate 1 in this order along the plane direction of the substrate 1.
The p-type semiconductor region 11 and the n-type semiconductor region 13 of the photodiode 10 are connected to source wiring films 8, 8 through wiring 7, 7 disposed in contact holes formed through a gate insulating film 4, an interlayer insulating film 5, and a planarizing layer 6. The planarizing layer 6 is usually constituted of an insulating material and also has a function as an insulating layer. The source wiring films 8, 8 become lead-out electrodes for driving the photodiode 10.
Here, as explained in the description of the conventional art using
As shown in
A transparent electrode film 25 is disposed on the protection film 9 including a region on the front surface of the photodiode 10 where the protection film 9 is removed. The transparent electrode film 25 is a transparent electrode film provided when pixel electrodes of a display device are formed and is made of ITO or IZO.
According to the photodiode 10 of the structure shown in
Also, even when the transparent electrode film 25 is not provided, because there is no insulating layer (protection film 9) that causes the entrapment of electric charge, the characteristic changes of the photodiode 10 can be suppressed. However, the even better result can be expected when the transparent electrode film 25 is provided.
That is, because the same voltage as the voltage applied to pixel will be applied to the transparent electrode film 25, the transparent electrode film 25 will be maintained at a constant voltage. When a transparent electrode is not provided, if there is electric charge trapped in the top surface of the upper portion of the light receiving layer, the diode characteristics will change over time because of the change in capacitance between the top surface and the i-type semiconductor region (12) that forms a light receiving layer, which includes the gate insulating film 4, the interlayer insulating film 5, and the planarizing layer 6. By providing the transparent electrode film 25 over a light receiving portion, however, capacitance generated in the gate insulating film 4, the interlayer insulating film 5, and the planarizing layer 6 can be maintained constant and more stable diode characteristics can be thereby obtained.
The photodiode 10 may be used for detection of ambient light of a display device so as to adjust the brightness of the display device itself in accordance with the brightness of the ambient light. This makes it possible to provide the optimal viewing whether indoors or outdoors because the ambient light in which the display device is used is detected, and in accordance with the brightness thereof, the display brightness of the display device itself is adjusted. Also, because unnecessarily bright display can be avoided, the energy consumption can be reduced.
Additionally, the photodiode 10 may be provided outside of a display region of a display device. In this manner, because the ambient light in which a display device is used can be detected at a spot that is, although outside of a display region, very close to the display region, in a manner similar to above, the display brightness of a display device itself is displayed in accordance with the brightness of the ambient light, and the optimal viewing can be made possible whether indoors or outdoors. Also, because unnecessarily bright display can be avoided, the energy consumption can be reduced. In this case, there is no need to form a photodiode in a display region, therefore, the density of display elements in the display region can be enhanced, and also the aperture ratio as a display device can be improved as well.
Additionally, the photodiode 10 may be configured adjacent to each pixel in a display region of a display device to obtain a display device provided with a photodiode that can be used for image capturing or for a touch panel. With this structure, image capturing can be done by a plurality of photodiodes that have less characteristic changes with a high degree of reliability, and thereby, the high quality image capturing can be provided over a long period of time. Also, when it is used as a touch panel, because the stable detection of a finger or the like can be performed, a high quality touch panel capable of responding to complex movements and the like can be configured.
The photodiode may also be formed for each pixel adjacent to each pixel, or one photodiode may be formed for a plurality of pixels. Further, the photodiode may be formed in a certain region only, such as, for example, forming only display pixels in the upper half of a display device and forming a photodiode adjacent to each pixel in the lower half. It is apparent that one photodiode may be formed for a plurality of pixels in this case too.
Also, in
In
First, on one surface of the glass substrate 1 that becomes a base, an insulator made of Si or the like or a metal film made primarily of an element, such as Ta, Ti, W, Mo, or Al, which will become a light shielding film, is formed by a CVD (chemical vapor disposition) method, a sputtering method, or the like. The acceptable film thickness is 50 nm or more, for example. Next, a resist pattern is formed using photolithography in a portion that overlaps a formation region of a light shielding film on a silicon film used for a photodiode. Thereafter, the insulating film or the metal film is etched using the resist pattern as a mask to obtain a light shielding film 2. This light shielding film 2 needs to be provided when a back light and the like is placed below
Thereafter, a base coat insulating film 3 is formed so as to cover the light shielding film 2. The base coat insulating film 3 can be formed by forming a silicon oxide film or a silicon nitride film using the CVD method, for example. Also, the base coat insulating film 3 may be either single-layered or multiple-layered. The thickness is set in a range of about 100 nm to 500 nm, for example.
Further, on the base coat insulating film 3, a silicon film 20 that becomes a photodiode is formed by the CVD method or the like. The silicon film 20 is made of continuous grain silicon or low temperature polysilicon. The low temperature polysilicon film is formed by the following steps, for example. First, a silicon oxide film and an amorphous silicon film are formed on the base coat insulating film 3 in this order. Next, laser annealing is performed to the amorphous silicon film to promote the crystallization. The silicon film 20 formed of low temperature polysilicon is thereby obtained.
In this embodiment, the silicon film 20 made of low temperature polysilicon is also used as a silicon film that constitutes a TFT as an active element (not shown in the figure). That is, the formation of the above described silicon film 20 can be performed using a formation step of a silicon film that constitutes a TFT.
Next, patterning of the silicon film 20 is performed.
Next, a gate insulating film 4 that becomes an interlayer insulating film is formed on the patterned silicon film 21.
Next, in order to adjust dosage of the patterned silicon film 21, ion implantation is performed using impurities of p-type such as boron (B) or indium (In), and setting the implantation energy in a range of 10 keV to 80 KeV, and the dosage in a range of 5×1014 (ion) to 2×1016 (ion), for example. It is preferable to set the impurity concentration after implantation to be in a range of 1.5×1020 to 3×1021 (atom/cm3) approximately. In this manner, a silicon film 22, which has been patterned and whose dosage has been adjusted, can be obtained as shown in
Next, as shown in
a) and 3(b) are diagrams for explaining steps of performing requisite ion implantations to the patterned silicon film 22, which has been adjusted in dosage, in order to form the p-type semiconductor region 11 and the n-type semiconductor region 13, thereby forming the photodiode 10 of PiN configuration.
a) is a diagram for explaining a step of performing ion implantation to form a diffusion layer of p-type. First, a resist pattern 31 is formed on the gate insulating film 4 using a photolithography technique. The resist pattern 31 has an opening in a portion that overlaps the p-type semiconductor region 11 of the photodiode 10, which will be created eventually. Next, ion implantation is performed using p-type impurities, such as boron (B) or indium (In), with the implantation energy in a range of 10 keV to 80 KeV and the dosage in a range of 5×1014 (ion) to 2×1016 (ion), for example. It is preferable that the impurity concentration after implantation be in a range of 1.5×1020 to 3×1021 (atom/cm3) approximately. After the ion implantation, the resist pattern 31 is removed.
Next, ion implantation is performed to form a diffusion layer of n-type.
When this ion implantation is finished, the photodiode 10 having the p-type semiconductor region 11, the i-type semiconductor region 12, and the n-type semiconductor region 13 is formed as shown in
Next, as shown in
Wiring 7 is formed in the contact holes, and necessary etching is performed to a source wiring layer on the photodiode 10 formed simultaneously with a formation of a source wiring layer in a TFT region to form the source wiring films 8, 8. Specifically, first, a conductive layer is formed using a single element of tantalum (Ta), titanium (Ti), tungsten (W), molybdenum (Mo), aluminum (Al) or the like, or a metallic material made primarily of an aforementioned element by sputtering or vacuum evaporation. Next, a resist pattern of a desired shape is formed by photolithography, and using this resist pattern as a mask, the conductive layer is etched. Further, as shown in
In the protection film 9, an opening needs to be formed to electrically connect a pixel electrode, which will be formed later, to a TFT for driving the pixel electrode. At the same time of forming this opening, the protection film 9 in a region above the photodiode 10 is removed to form an opening as shown in
A photodiode that has less changes in its characteristics can be thereby obtained. Therefore, when a liquid crystal panel module with a touch panel incorporating such an optical sensor is made, for example, reliability of the optical sensor is ensured.
Although the above explanation has been made using an example of a photodiode of PiN configuration, the similar effect can be expected with not only the photodiode of PiN configuration, but also other configurations (such as PI Schottky, for example).
As described above, although the figures in the above description specifically show the photodiode areas only, it is apparent that the optical sensor can be manufactured simultaneously with the manufacturing process for a TFT and the like as an active element in a display region, and a photodiode can also be formed for each pixel.
Also, the present invention is not limited to each embodiment described above. Various modifications of the present invention may be made by those skilled in the art within the scope defined by the claims. That is, additional embodiments can be obtained by combining technical means which are appropriately modified without departing from the scope defined by the claims.
To solve the above-mentioned problem, another photodiode according to the present invention is characterized in that the photodiode is formed by a semiconductor film having a p-type semiconductor region, an i-type semiconductor region, and an n-type semiconductor region formed on a substrate in this order along the plane direction of the substrate.
This makes it possible to provide a PIN type photodiode having a p-type semiconductor region, an i-type semiconductor region and an n-type semiconductor region, which has less changes in output characteristics even with the prolonged use.
To solve the above-mentioned problem, another photodiode according to the present invention is characterized in that a transparent electrode film is formed on the protection film.
This makes it possible to provide a photodiode with more stable characteristics because the same voltage signal as that applied to a pixel can be sent onto the transparent electrode film, and therefore, the transparent electrode film can be maintained at a constant voltage.
To solve the above-mentioned problem, another photodiode according to the present invention is characterized in that a light receiving portion of the photodiode where the protection film is not provided is a portion corresponding to the i-type semiconductor region of the photodiode.
This leads to the effect of eliminating adverse effect to the planarization of the surface because the removed portion of the protection film can be kept to a minimum. Additionally, in this case, because an opening is provided adjacent to the light receiving portion of the photodiode, small reflection of light is generated from wall surfaces of the opening, resulting in another effect of the enhancement of light receiving efficiency.
To solve the above-mentioned problem, another display device according to the present invention is characterized in that the active element is a TFT, and the wiring film is a wiring film that is formed when source wiring of the TFT is formed.
This makes it possible to form a photodiode in the same process as a formation process of an active element, resulting in the effect of very easy manufacturing.
To solve the above-mentioned problem, another display device according to the present invention is characterized in that the photodiode detects ambient light of the display device, and the brightness of the display device is adjusted in accordance with the brightness of the ambient light.
This makes it possible to provide the optimal viewing whether indoors or outdoors because the display brightness of the display device itself can be adjusted in accordance with the ambient light in which the display device is used. Also, this makes it possible to avoid the display device being unnecessarily bright and thereby contributes to the reduction of energy consumption.
To solve the above-mentioned problem, a display device according to the present invention is characterized in that the photodiode is formed adjacent to a pixel in a display region and is used for image capturing or for a touch panel.
This makes it possible to install photodiodes over a wide area, and therefore, a display device that can capture images or can be used as a touch panel can be obtained.
The specific embodiments or examples described in the section of “Detailed Description Of Embodiments” are solely intended to clarify the technical aspects of the present invention, and shall not be interpreted narrowly to be limited to such specific embodiments, and accordingly, various modification may be made without departing from the spirit of the present invention as well as the scope defined by the claims below.
According to the present invention, a photodiode that has less changes in its characteristics even with the prolonged use can be obtained. Also, a display device provided with such a photodiode as an optical sensor that has less changes in its characteristics, which can be used as a touch panel, can be obtained. Applications of the display device are not limited to liquid crystal display devices, but include various display devices such as EL display devices. Because the display devices provided with such a photodiode are used in many fields, the industrial applicability is very high.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-049655 | Mar 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/000627 | 2/3/2010 | WO | 00 | 9/2/2011 |
