Patent Application
20150255616
The present invention relates to a semiconductor device and a display device.
In order to respectively control the operation of the pixels, the liquid crystal panels of liquid crystal display devices have switching elements that are thin-film transistors (hereinafter, TFT) arranged in a matrix (rows and columns). Conventionally, silicon semiconductors such as amorphous silicon were generally used as semiconductor films for TFTs. However, the usage of oxide semiconductors having high electron mobility as semiconductor films has been proposed recently. Patent Documents 1 to 3 disclose liquid crystal display devices adopting TFTs using these types of oxide semiconductors as switching elements. The usage of oxide semiconductors having high electron mobility can provide improvements such as size reduction of the TFTs compared to conventional products and improvement in the aperture ratio of the liquid crystal panel.
Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2004-103957
Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2006-165528
Patent Document 3: Japanese Patent Application Laid-Open Publication No. 2007-73705
The electrical characteristics of oxide semiconductors are susceptible to degradation when the oxide semiconductors come into contact with moisture. Therefore, there is a risk that the switching elements will not operate properly if moisture enters the TFTs using oxide semiconductors from outside, other films, and the like.
The object of the present invention is to provide a semiconductor device and a display device including the semiconductor device, in which the semiconductor device has a feature that suppresses foreign materials such as moisture from entering an oxide semiconductor film.
A semiconductor device of the present invention, having: a semiconductor film made of an oxide semiconductor film and having a channel region; a protective film formed on the semiconductor film so as to cover the channel region; a first inorganic insulating film formed on the protective film and having a portion overlapping the channel region; and an organic insulating film made of a resin film and formed on the first inorganic insulating film, the organic insulating film having a first opening to expose the first inorganic insulating film in an area overlapping the channel region.
In the semiconductor device, the semiconductor film formed of an oxide semiconductor film has a channel region, and a protective film is formed on the semiconductor film so as to cover the channel region. In addition, the first inorganic insulating film having a portion overlapping the channel region is formed on the protective film. Furthermore, the organic insulating film formed of a resin film is formed on the first inorganic insulating film. This organic insulating film has a first opening that exposes the first inorganic insulating film in an area overlapping the channel region. In other words, the organic insulating film is not formed in an area that overlaps with the channel region. If the organic insulating film has a first opening in an area that overlaps the channel region, then foreign materials such as moisture are suppressed from moving towards the semiconductor film from outside through the organic insulating film. Even if foreign materials such as moisture move toward the semiconductor film, the channel region of the semiconductor film is covered by the protective film and the channel region of the semiconductor film is protected from foreign materials such as moisture. Thus, by the semiconductor device having the configuration mentioned above, the electrical characteristics of the semiconductor film are suppressed from degrading due to foreign materials such as moisture coming into contact therewith.
The semiconductor device may have: a first electrode formed of a conductive film and overlapping the organic insulating film, the first electrode being electrically connected to the semiconductor film through a second opening formed through the first inorganic insulating film and the organic insulating film in a location that does not overlap the channel region.
The semiconductor device may have: a substrate; a second electrode provided on the substrate; and a second electrode side insulating film formed on the substrate so as to cover the second electrode, wherein the semiconductor film is formed on the second electrode side insulating film.
The semiconductor device may have: a second inorganic insulating film between the organic insulating film and the first electrode such that the second inorganic insulating film fills the first opening. If the first opening is filled by the second inorganic insulating film, then foreign materials such as moisture become less likely to move towards the semiconductor film through the first opening. As a result, water resistance (moisture transmittance resistance) of the semiconductor film (channel region, in particular) improves.
The semiconductor device may have: a third electrode between the organic insulating film and the second inorganic insulating film such that the third electrode fills the first opening, the third electrode being made of a conductive film and facing the first electrode. If the third electrode formed of the conductive film is in the first opening, then foreign materials such as moisture become less likely to move towards the semiconductor film through the first opening. As a result, water resistance (moisture transmittance resistance) of the semiconductor film (channel region, in particular) improves.
The semiconductor device may have: a pair of fourth and fifth electrodes each having a contact portion in direct contact with a surface of the semiconductor film, the fourth and fifth electrodes facing each other across the channel region, wherein the protective film is formed so as to cover a portion of a surface of the semiconductor film that is not in contact with the contact portions. In the semiconductor device, the channel region of the semiconductor film is more reliably protected from moisture and the like, because the protective film covers a portion of the surface of the semiconductor film that is not in contact with the contact portion. In addition, the semiconductor film including the channel region can be protected from moisture and the like even when the fourth electrode and the fifth electrode are being formed and the like.
The organic insulating film of the semiconductor device may be formed of an acrylic resin. Although acrylic resin has a characteristic of easily acquiring moisture and thus has a risk of oxidizing the semiconductor film, because the first opening is formed in the organic insulating film (in other words the organic insulating film is not formed in an area overlapping the channel region), moisture is suppressed from moving towards the semiconductor film from outside through the organic insulating film. As a result, even if the acrylic resin is used as the organic insulating film, the electrical characteristics of the semiconductor film are suppressed from changing (degrading).
The semiconductor film of the semiconductor device may be formed of an oxide including at least one element selected from a group having indium (In), gallium (Ga), aluminum (Al), copper (Cu), zinc (Zn), and tin (Sn). If the semiconductor film of the semiconductor device has the above-mentioned configuration, the electron mobility of the semiconductor film is high even if the semiconductor film is amorphous, and the ON resistance of the switching element can be increased.
The semiconductor film of the semiconductor device may be formed of indium gallium zinc oxide. If the semiconductor film of the semiconductor device is formed of indium gallium zinc oxide, then excellent characteristics of high mobility and low OFF current can be obtained.
The protective film of the semiconductor device may be formed of silicon oxide. Compared to silicon nitride, organic insulating material, and the like, silicon oxide is a material that is less likely to oxidize or reduce the semiconductor film and can suppress the electrical characteristics of the semiconductor film from changing (degrading), for example.
The semiconductor film of the semiconductor device may be formed on the second electrode side insulating film so as to overlap the second electrode.
The semiconductor device, wherein the protective film may fits inside the first opening in a plan view. If the first opening is formed such that the protective film fits inside the opening in a plan view, then, because foreign materials such as moisture are farther away from the protective film, the foreign materials such as moisture are suppressed from moving towards the semiconductor film through the organic insulating layer and entering the semiconductor film from the periphery of the protective film by moving along the surface thereof.
The semiconductor device, wherein the second electrode side insulating film may have a multilayer structure having a bottom layer second electrode side insulating film formed of silicon nitride and a top layer second electrode side insulating film formed of silicon oxide disposed between the bottom layer second electrode side insulating film and the semiconductor film. Silicon oxide is a material that is less likely to oxidize or reduce the semiconductor film compared to silicon nitride, organic insulating material, and the like, for example. The electrical characteristics of the semiconductor film are suppressed from changing (degrading) by disposing the top layer second electrode side insulating film formed of silicon oxide between the bottom layer second electrode side insulating film and the semiconductor film.
A display device according to the present invention has: the semiconductor device; an opposite substrate facing the semiconductor device; and a liquid crystal layer disposed between the semiconductor device and the opposite substrate. If the display device has the configuration mentioned above, the electrical characteristics of the semiconductor film are suppressed from changing (degrading) and the display device has excellent operational reliability and the like.
The object of the present invention is to provide a semiconductor device that suppresses foreign materials such as moisture from entering a semiconductor film formed of an oxide semiconductor, and a display device including the semiconductor device.
Embodiment 1 of the present invention will be explained below with reference to
As shown in
The backlight device 12 is a device for supplying light to the liquid crystal panel 11 of the liquid crystal module LM and is attached to the rear surface (back side) side of the liquid crystal module LM (liquid crystal panel 11). The backlight device 12 mainly includes a chassis 12a having a substantially box shape that is open towards the front side (liquid crystal panel 11 side), a light source (not shown) housed in the chassis 12a, and an optical sheet (not shown) that is provided so as to cover the opening of the chassis 12a and that emits planar light by transmitting the light from the light source. An LED, a cold cathode fluorescent lamp, or the like is used as the light source, for example. In addition, the optical sheet adjusts the light emitted from the light source into a uniform and planar light.
The backlight device 12 and the liquid crystal panel 11 that are attached to each other are housed and held by a pair of front and back exterior members (case) 16 and 17. The front exterior member 16 has a substantially frame shape when seen in a plan view from the front side and an opening 16a is provided in the central portion thereof. The display area AA of the liquid crystal panel 11 is exposed through this opening 16a such that the display area AA is seen by the user.
The flexible substrate 15 has a resin base material formed of a synthetic resin material (polyimide resin or the like, for example) that is insulating and flexible, and has a plurality of wiring patterns (not shown) formed on the resin base material. The flexible substrate 15 has a belt-shape as a whole and a control circuit substrate 14 is connected to an edge portion thereof. Furthermore, an edge portion of the liquid crystal panel 11 is connected to another edge portion of the flexible substrate 15. The input signal supplied from the control circuit substrate 14 side is transmitted to the liquid crystal panel 11 side by the flexible substrate 15. The flexible substrate 15 is housed within the liquid crystal display device 10 in a bent state such that the cross-section of the flexible substrate 15 is in a substantially U shape.
The driver 13 is formed of an LSI chip having a driving circuit therein, and the driver 13 is activated based on a signal supplied from the control circuit substrate 14, which is a signal supplying source. If the driver 13 is activated in this manner, then the driver 13 processes the input signal supplied by the control circuit substrate 14 and generates an output signal. Then, the output signal is outputted towards the liquid crystal panel 11. The driver 13 is directly mounted onto the non-display area NAA of the rear surface side substrate (array substrate 11b mentioned later) of the liquid crystal panel 11 using a so-called COG (chip on glass) method.
The liquid crystal display device 10 of the present embodiment is used in various electronic devices such as a mobile information device (including electronic books, PDAs, and the like), mobile telephones (including smartphones), laptops (including tablet PCs and the like), digital photo frames, portable gaming devices, and electronic ink papers. The liquid crystal panel 11 used in the liquid crystal display device 10 of the present embodiment is usually categorized as small or medium small, and the screen size thereof ranges between several inches to several dozen inches.
The liquid crystal panel 11 will be described here in detail. As shown in
The operation mode of the liquid crystal panel 11 of the present embodiment is commonly known as the FFS (fringe field switching) mode, which is a lateral electric field mode in which a pair of electrodes are provided on one substrate 11b and an electric field is applied to the liquid crystal molecules in a direction parallel (horizontal) to the substrate surface. Therefore, the array substrate (an example of a semiconductor device) 11b of the present embodiment has a pair of electrodes (pixel electrode 19 and common electrode 30 mentioned later) formed thereon.
The CF substrate 11a and the array substrate 11b both have substantially transparent glass substrates with high light-transmissive characteristics, and are formed of various films that are stacked on the glass substrate in a prescribed pattern. As shown in
In addition, alignment films (not shown) for aligning the liquid crystal molecules included in the liquid crystal layer 11c are respectively formed on the inner surface side of the two substrates 11a and 11b. Furthermore, polarizing plates (not shown) are bonded on the respective outer surfaces of the two substrates 11a and 11b.
The CF substrate 11a has respective colored portions (CF, not shown) of R (red), G (green), and B (blue) arranged in a matrix. The colored portions are respectively allotted to the pixels and overlap the respective pixel electrodes of the array substrate 11b (described later) in a plan view. Furthermore, the respective colored portions of the CF substrate 11a are separated by the grid shaped black matrix (not shown) having light-shielding characteristics. The black matrix overlaps the gate wiring lines and the source wiring lines on the array substrate 11b (mentioned later) in a plan view. The alignment film is formed on the respective colored portions and the black matrix. In addition, in the CF substrate 11a of the present embodiment, one display pixel (picture element) that is a display unit of the liquid crystal panel 11 is formed of a group of three colored portions: R (red), G (green), and B (blue).
Next, with reference to
The TFT 18 has a gate electrode (second electrode) 18a that extends from the gate wiring line 20, a semiconductor film 23 having a channel region 18b, a source electrode (fourth electrode) 18c extending from the source wiring line 21, and a drain electrode (fifth electrode) 18d. The source electrode 18c and the drain electrode 18d are disposed on the semiconductor film 23 while sandwiching the channel region 18b such that the source electrode 18c and the drain electrode 18d face each other with a gap therebetween. The source electrode 18c and the drain electrode 18d are both electrically connected to the semiconductor film 23.
A substrate 22 is formed of a glass substrate, a silicon substrate, or an insulating substrate having heat resistance such as a plastic substrate. It is preferable that a transparent substrate such as a glass substrate that transmits light be used as the substrate 22 for the liquid crystal display device 10 of the present embodiment. A glass substrate is used as the substrate 22 in the present embodiment.
Gate wiring lines 20 formed of a first metal film M1, a gate electrode 18a, and the like are formed on the surface of the substrate 22 facing inward (liquid crystal layer 11c side). Furthermore, a gate insulating film (second electrode side insulating film) 24 is formed on the substrate 22 such that the gate insulating film 24 covers the gate wiring lines 20 and the like formed of a first metal film M1. Furthermore, the semiconductor film 23 formed of an oxide semiconductor film, source wiring lines 21 formed of a second metal film M2, the source electrode 18c, the drain electrode 18d, and the like are formed on the gate insulating film 24.
A protective film (etch stop film) 31 is formed on the semiconductor film 23 so as to cover at least the channel region 18b. In the present embodiment, the protective film 31 is mainly formed between the source electrode 18c and the drain electrode 18d (in other words, on the channel region 18b) that are on the semiconductor film 23 and facing each other. As shown in
A first interlayer insulating film (first non-organic insulating film) 25 is formed on the gate insulating film 24 so as to cover the semiconductor film 23 that has the protective film 31 formed thereon, the source wiring line 21, and the like. An organic insulating film 26 is formed on the first interlayer insulating film 25, and a common electrode (third electrode) 30 formed of a transparent conductive film is formed on the organic insulating film 26. In addition, the second interlayer insulating film (second inorganic insulating film) 27 is formed so as to cover the common electrode 30, and the pixel electrode (first electrode) 19 made of a transparent conductive film is formed on the second interlayer insulating film 27. The first interlayer insulating film (first inorganic insulating film) 25, the common electrode (third electrode) 30, the second interlayer insulating film (second inorganic insulating film) 27, and the pixel electrode (first electrode) 19 are all formed on the array substrate 11b so as to cover the TFT 18 (in other words, includes a portion that covers the channel region 18b of the TFT 18). However, the organic insulating film 26 has an opening 26a that overlaps the channel region 18b of the TFT 18 in a plan view. This opening 26a is a hole penetrating the organic insulating film 26 in the thickness direction.
This first metal film M1 is formed of a layered film of titanium (Ti) and copper (Cu). The first metal film M1 is configured such that a film M1a formed of titanium (Ti) is disposed on the bottom layer side and a film M1b formed of copper (Cu) is disposed on the top layer side. The first metal film M1 is formed on the substrate 22 by sputtering or the like. Then, the gate wiring line 20 formed of the first metal film M1 having a prescribed pattern, the gate electrode 18a, and the like are formed on the substrate 22 by performing photolithography and wet etching the copper (Cu) film M1b, and by also performing dry etching, removal and washing of the resist, and the like to the titanium (Ti) film M1a.
The gate insulating film (second electrode side insulating film) 24 is formed as a layered film having a bottom layer gate insulating film (bottom layer second electrode side insulating film) 24a formed of silicon nitride (SiNx) and a top layer gate insulating film (top layer second electrode side insulating film) 24b formed of silicon oxide (SiOx, x=2, for example). The gate insulating film 24 is formed using the CVD method or the like as appropriate.
The semiconductor film 23 is formed of a film of indium gallium zinc oxide, which is a type of an oxide semiconductor. The indium gallium zinc oxide film that forms the semiconductor film 23 is amorphous or crystalline, and especially if the film is crystalline, then the film has a crystalline structure known as a c-axis aligned crystal. The semiconductor film 23 forms the channel region 18b and the like of the TFTs 18. Meanwhile, the semiconductor film 23 is not only used for TFTs that are for display, but also for the TFTs that are not for display (not shown) and the like disposed in the non-display area NAA. The semiconductor film 23 is formed with a prescribed pattern on the gate insulating film 24 by forming the indium gallium zinc oxide film by sputtering and then performing photolithography, wet etching, resist removal and washing, and the like on the indium gallium zinc oxide film.
The protective film 31 is formed of silicon oxide (SiOx, in which x=2, for example). This protective film 31 is formed by performing photolithography, etching, resist removal and cleaning, and the like on the silicon oxide film formed by the plasma CVD method or the like. If the protective film 31 is formed on the array substrate 11b such that the protective film 31 at least covers the channel region 18b of the semiconductor film 23, then the channel region 18b is protected from foreign material such as moisture during the production of the array substrate 11b (in particular, during the processing of a second metal film M2 of the source electrode 18c and the like). In addition, after the array substrate 11b is manufactured, even when the array substrate is mounted on the display device, if the protective film 31 is formed so as to cover the channel region 18b of the semiconductor film 23, then foreign materials such as moisture are suppressed from entering the channel region 18b of the semiconductor film 23 and the degradation of the semiconductor film 23 is suppressed. Compared to silicon nitride, organic insulating material, and the like, silicon oxide is a material that is less likely to oxidize or reduce the semiconductor film 23, and can suppress the change (degradation) of the electrical characteristics of the semiconductor film 23.
The second metal film M2 is formed of a layered film of titanium (Ti) and copper (Cu). The second metal film M2 has a film M2a formed of titanium (Ti) disposed on the bottom layer side and a film M2b formed of copper (Cu) disposed on the top layer side. The second metal film M2 is formed on the gate insulating film 24 by sputtering or the like. In addition, the source wiring line 21 formed of the second metal film M2 having a prescribed pattern, the source electrode 18c, the drain electrode 18d, and the like are formed on the gate insulating film 24 by performing photolithography and wet etching to the copper (Cu) film M2b while performing dry etching, resist removal and washing, and the like to the titanium (Ti) film M2a. Then, the channel region 18b of the semiconductor film 23 that is covered by the protective film 31 is formed between the source electrode 18c and the drain electrode 18d.
The channel region 18b of the TFT 18 is mainly formed of a portion (region) of the semiconductor film 23 that is sandwiched between the source electrode 18c and the drain electrode 18d, and electrons can move between the source electrode 18c and the drain electrode 18d. As mentioned above, the semiconductor film 23 of the present embodiment is an indium gallium zinc oxide film and the electron mobility thereof, when compared to conventional amorphous silicon films and the like, is approximately twenty to fifty times higher. As a result, the TFTs 18 that use an indium gallium zinc oxide film (semiconductor film 23) can be reduced in size compared to conventional TFTs and the aperture ratio of the display region (pixel P) can be increased. The TFT 18 on the substrate 22 has the gate electrode 18a provided on the bottom layer and the channel region 18b of the semiconductor film 23 stacked on the gate electrode 18a through the gate insulating film 24. In other words, the TFT 18 is a so-called inverse staggered type (bottom gate type).
The opening (contact hole, second opening) 29 for exposing a portion of the drain electrode 18d is formed in the first interlayer insulating film (first inorganic insulating film) 25, the organic insulating film 26, and the second interlayer insulating film (second inorganic insulating film) 27. The opening 29 penetrates the first interlayer insulating film 25, the organic insulating film 26, and the second interlayer insulating film 27. Furthermore, the opening (contact hole) 29 is provided in a location that does not overlap the semiconductor film 23 and the channel region 18b.
The first interlayer insulating film (first inorganic insulating film) 25 is made of silicon oxide (SiOx, in which x=2, for example), and is formed by the plasma CVD method or the like so as to cover the source electrode 18c, the drain electrode 18d, the semiconductor film 23, and the like. It is preferable that the first interlayer insulating film (first inorganic insulating film) 25 be formed of the same material as the protective film 31. If the first interlayer insulating film (first inorganic insulating film) 25 and the protective film 31 are formed of the same material (silicon oxide, for example), then the first interlayer insulating film (first inorganic insulating film) 25 and the protective film 31 can closely adhere to each other with ease, and thereby suppress foreign materials such as moisture from entering between the first interlayer insulating film (first inorganic insulating film) 25 and the protective film 31.
The organic insulating film 26 is formed of an acrylic resin material that is an organic material (polymethyl methacrylate (PMMA) or the like, for example) and functions as a planarizing film. It is preferable that the acrylic resin material be photosensitive. The organic insulating film 26 is formed so as to cover substantially the entire display area AA of the array substrate 11b. However, in an area that overlaps the channel region 18b of the semiconductor film 23 (TFT 18) in a plan view, the organic insulating film 26 has an opening (first opening) 26a that is a hole penetrating the organic insulating film 26. The opening 26a is provided for each TFT 16 (semiconductor film 23) of each pixel P. As shown in
In particular, in the case of the present embodiment, the opening 26a is configured to be larger than the protective film 31 formed on the semiconductor film 23 in a plan view. As a result, the protective film 31 fits inside the opening 26a in a plan view. The organic insulating film 26 is applied on the first interlayer insulating film 25 by spin coating, slit coating, or the like, for example. In addition, the organic insulating film 26 having the opening 26a in a prescribed location is formed on the first interlayer insulating film 25 using known photolithography techniques or the like. When the array substrate 11b is being formed (in other words, before the common electrode 30 and the like is formed), the first interlayer insulating film 25 is exposed through the opening 26a of the organic insulating film 26.
The common electrode (third electrode) 30 is formed of a transparent conductive film such as ITO (indium tin oxide) and ZnO (zinc oxide). The common electrode 30 is formed on the organic insulating film 26 so as to cover a plurality of pixels P such that the plurality of pixels P share the common electrode 30. The common electrode P is formed on the organic insulating film 26 so as to cover substantially the entire display area AA of the array substrate 11b. Meanwhile, the common electrode 30 is formed so as to cover the tube-shaped inner surface of the opening 26a of the organic insulating film 26, and also cover the surface of the first interlayer insulating film 25 that is exposed from the bottom side of the opening 26a. In addition, a portion of the common electrode 30 that is formed in the opening 26a is formed so as to cover the channel region 18b of the TFT 16 (semiconductor film 23). The common electrode 30 formed in the opening 26a has a recessed shape. In other words, the opening 26a is buried under the common electrode 30 with some remaining air gaps inside.
In addition, the common electrode 30 has an opening 30a that is a hole penetrating the common electrode 30 in the thickness direction. The opening (contact hole) 29 is formed inside the opening 30a such that the opening (contact hole) 29 penetrates the first interlayer insulating film 25, the organic insulating film 26, and the second interlayer insulating film 27 in a plan view. As a result, one opening is formed by the opening 29 provided on the first interlayer insulating film (first inorganic insulating film) 25, the organic insulating film 26, and the second interlayer insulating film (second inorganic insulating film) 27 and the opening 30a provided on the common electrode (third electrode) 30.
The transparent conductive film used for the common electrode 30 is formed on the second interlayer insulating film 27 by sputtering, for example. Then, a common electrode 30 having a prescribed pattern is formed by performing photolithography, wet etching, resist removal and washing, and the like on the transparent conductive film. The common electrode (third electrode) 30 is sandwiched between the organic insulating film 26 and the second interlayer insulating film (second inorganic insulating film) 27. However, the portion of the common electrode 30 that is disposed on the opening (first opening) 26a is sandwiched between the first interlayer insulating film (first inorganic insulating film) 25 and the second interlayer insulating film (second inorganic insulating film) 27.
The second interlayer insulating film (second inorganic insulating film) 27 is made of a silicon nitride (SiNx) that is an inorganic insulating film, and is formed on the common electrode 30 using the plasma CVD method or the like so as to cover the channel region 18b. The second interlayer insulating film 27 is formed on the common electrode 30 so as to cover substantially the entire display area AA of the array substrate 11b. Meanwhile, the second interlayer insulating film 27 is provided in the opening 26a of the common electrode 30 having a recessed shape so as to bury the recessed shape portion.
The pixel electrode (first electrode) 19 is formed of a transparent conductive film such as ITO (indium tin oxide) and ZnO (zinc oxide) in a similar manner to the common electrode 30. The pixel electrode 19 is disposed so as to fit in the rectangular region (pixel P) surrounded by the gate wiring lines 20 and the source wiring lines 21 when the array substrate 11b is seen in a plan view. Furthermore, the pixel electrode 19 is mainly formed on the second interlayer insulating film (second inorganic insulating film) 27. When seeing the array substrate 11b in a plan view, the pixel electrode 19 has a rectangular main body 19a covering the pixel P region, an overlapping portion 19b that overlaps the TFT 18, and a connecting portion 19c that connects with the drain electrode 18d through the opening (contact hole) 29. The pixel electrode 19 is electrically connected to the semiconductor film 23 of the TFT 18 by being connected to the drain electrode 18d through the opening 29 of the connecting portion 19c.
The main body 19a has a plurality of slits 19d extending with a narrow shape along the alignment direction (Y axis direction) of the source wiring lines 21. Three slits 19d are provided in the present embodiment. The slits 19d are arranged on the main body 19a at even intervals.
The overlapping portion 19b is a portion of the pixel electrode 19 and is formed of a transparent conductive film such as ITO. When the array substrate 11b is seen in a plan view, the TFT 18 is inside the overlapping portion 19b. Thus, in a plan view, the overlapping portion 19b overlaps the semiconductor film 23 (channel region 18b) of the TFT 18 such that the semiconductor film 23 is inside the overlapping portion 19b.
The pixel electrode 19 is formed by performing photolithography, wet etching, resist removal and washing, and the like on a transparent conductive film such as ITO formed by sputtering, for example.
The main body 19a and the overlapping portion 19b of the pixel electrode 19 face the common electrode 30 through the second interlayer insulating film 27. A common potential (reference potential) is applied to the common electrode 30 from a common wiring line (not shown). In addition, by controlling the potential applied to the pixel electrode 19 by the TFTs 18, a prescribed difference in potential is generated between the pixel electrode 19 and the common electrode 30.
If a prescribed difference in potential is generated between the pixel electrode 19 and the common electrode 30, then in the liquid crystal layer 11c between the array substrate 11b and the CF substrate 11a, the pixel electrode 19 having the slits 19d applies a fringe electric field (diagonal electric field) along a surface of the array substrate 11b and along a direction normal to the surface of the array substrate 11b. By controlling this electric field as appropriate, the alignment of the liquid crystal molecules within the liquid crystal layer 11c can be switched as appropriate.
As mentioned above, the array substrate (semiconductor device) 11b used in the liquid crystal display device 10 of the present embodiment is formed of an oxide semiconductor film, and includes the semiconductor film 23 having the channel region 18b, the protective film 31 formed on the semiconductor film 23 so as to cover the channel region 18b, the first interlayer insulating film (first inorganic insulating film) 25 formed on the protective film 31 so as to overlap the channel region 18b of the semiconductor film 23 from above, and the organic insulating film 26 made of a resin film and formed on the first interlayer insulating film (first inorganic insulating film) 25, in which the first opening 26a is formed in a portion of the first interlayer insulating film (first inorganic insulating film) 25 that overlaps the channel region 18b so as to expose the first interlayer insulating film (first inorganic insulating film) 25.
If the organic insulating film 26 has the first opening 26a in a portion overlapping the channel region 18b (in other words, if the organic insulating film 26 is formed in an area overlapping the channel region 18b), then foreign materials from outside (air and liquid crystal layer 11c, for example) such as moisture is suppressed from moving towards the semiconductor film 23 through the organic insulating film 26. Even if foreign materials such as moisture move towards the semiconductor film 23, the channel region 18b of the semiconductor film 23 is protected from foreign materials such as moisture because the channel region 18b of the semiconductor film 23 is covered by the protective film 31 having water resistance (moisture transmission resistance). Therefore, by having the configuration mentioned above, the array substrate (semiconductor device) 11b suppresses the electrical characteristics of the semiconductor film 23 from degrading due to contacting foreign materials such as moisture.
In addition, the array substrate 11b of the present embodiment has a first electrode 19 that is formed of a conductive film overlapping the organic insulating film 26, and has the first electrode 19 electrically connected to the semiconductor film 23 through the opening (second opening) 29 formed so as to penetrate the first interlayer insulating film (first inorganic insulating film) 25 and the organic insulating film 26 in a location that does not overlap the channel region 18b.
Furthermore, the array substrate 11b of the present embodiment has the substrate 22, the gate electrode (second electrode) 18a formed on the substrate 22, and the gate insulating film (second electrode side insulating film) 24 formed so as to cover the gate electrode (second electrode) 18a, in which the semiconductor film 23 is formed on the gate insulating film (second electrode side insulating film) 24.
In addition, the array substrate 11b of the present embodiment fills in the opening (first opening) 26a and has the second interlayer insulating film (second inorganic insulating film) 27 disposed between the organic insulating film 26 and the pixel electrode (first electrode) 19. If the opening (first opening) 26a is filled in by the second interlayer insulating film (second inorganic insulating film) 27, then foreign materials such as water is less likely to move towards the semiconductor film 23 through the opening (first opening) 26a. As a result, water resistance (moisture transmittance resistance) of the semiconductor film 23 (channel region 18b, in particular) improves.
Additionally, the array substrate 11b of the present invention has the common electrode (third electrode) 30 formed of a conductive film that is in the opening (first opening) 26a and that is disposed between the organic insulating film 26 and the second interlayer insulating film (second inorganic insulating film) 27 such that the common electrode 30 faces the pixel electrode (first electrode) 19. If the common electrode (third electrode) 30 formed of the conductive film is in the opening (first opening) 26a, then foreign materials such as water is less likely to move towards the semiconductor film 23 through the opening (first opening) 26a. As a result, water resistance (moisture transmittance resistance) of the semiconductor film 23 (channel region 18b, in particular) improves.
Also, the organic insulating film 26 of the array substrate 11b of the present embodiment is formed of an acrylic resin. Acrylic resin has characteristics of easily acquiring moisture, and thereby has a risk of causing oxidization or the like to the semiconductor film 23 with the moisture, but because the organic insulating film 26 has the opening (first opening) 26a, moisture moving to the semiconductor film 23 from outside (outer atmosphere and the liquid crystal layer 11c, for example) or the like through the organic insulating film 26 is suppressed. As a result, even if an acrylic resin is used for the organic insulating film 26, the change (degradation) of the electrical characteristics of the semiconductor film 23 is suppressed.
In addition, the semiconductor film 23 of the array substrate 11b of the present embodiment is formed of an oxide having at least one of an element in a group including indium (In), gallium (Ga), aluminum (Al), copper (Cu), zinc (Zn), and tin (Sn). If the semiconductor film 23 of the array substrate 11b of the present embodiment has this type of structure, even if the semiconductor film 23 is amorphous, the electron mobility is high, and the ON resistance of the switching element can be increased.
In addition, it is preferable that the semiconductor film 23 of the array substrate 11b in the present embodiment be formed of indium gallium zinc oxide. In particular, it is preferable that the semiconductor film 23 be an indium gallium zinc oxide film having the c-axis aligned crystal structure. If the semiconductor film 23 is formed of this type of indium gallium zinc oxide film, then excellent characteristics of high mobility and low OFF current can be obtained. The electrical characteristics of the semiconductor film 23 formed of an indium gallium zinc oxide and having the c-axis aligned crystal structure are particularly susceptible to changing (degrading) when foreign material such as moisture enters therein. As a result, if the array substrate 11b of the present embodiment has a group of inorganic films 28, the electrical characteristics of the semiconductor film 23 can, in particular, be effectively suppressed from degrading.
Also, in the array substrate 11b of the present embodiment, the protective film 31 of the array substrate 11b of the present embodiment is formed of a silicon oxide. Compared to silicon nitride, organic insulating material, and the like, silicon oxide is a material that is less likely to oxidize or reduce the semiconductor film 23, and can suppress the change (degradation) of the electrical characteristics of the semiconductor film 23.
In addition, in the array substrate 11b of the present embodiment, the semiconductor film 23 is formed on the gate insulating film (second electrode side insulating film) 24 so as to overlap the gate electrode (second electrode) 18a.
Also, if the opening (first opening) 26a of the array substrate 11b of the present embodiment fits inside the protective film 31 in a plan view, then, because foreign materials such as moisture that moves towards the semiconductor film 23 through the organic insulating film 26 is farther away from the protective film 31, the moisture and the like is suppressed from entering the semiconductor film 23 from the periphery of the protective film 31 by moving along the surface of the protective film 31.
In addition, the array substrate 11b of the present embodiment has a multilayer structure in which the gate insulating film (second electrode side insulating film) 24 has a bottom layer gate insulating film (bottom layer second electrode side insulating film) 24a formed of silicon nitride, and a top layer gate insulating film (top layer second electrode side insulating film) 24b formed of silicon oxide disposed between the bottom layer gate insulating film (bottom layer second electrode side insulating film) 24a and the semiconductor film 23. Silicon oxide is a material that is less likely to oxidize or reduce the semiconductor film 23 compared to silicon nitride, an organic insulating material, and the like, for example. By disposing this top layer gate insulating film (top layer second electrode side insulating film) 24b between the bottom layer gate insulating film (bottom layer second electrode side insulating film) 24a and the semiconductor film 23, the electrical characteristics of the semiconductor film 23 can be suppressed from changing (degrading).
In addition, the liquid crystal display device 10 according to the present embodiment includes the array substrate (semiconductor device) 11b, the CF substrate (opposite substrate) 11a disposed so as to face the array substrate (semiconductor device) 11b, and the liquid crystal layer 11c disposed between the array substrate (semiconductor device) 11b and the CF substrate (opposite substrate) 11a. If the liquid crystal display device 10 has the above-mentioned configuration, the electrical characteristics of the semiconductor film 23 is suppressed from changing (degrading) and has excellent operation reliability.
Next, Embodiment 2 of the present invention will be described using
The basic structure of the array substrate 111B of the present embodiment is similar to the structure in Embodiment 1. However, the array substrate 111b of the present embodiment is different from Embodiment 1 in that the array substrate 111b has a protective film (etch stop film) 31 disposed between the semiconductor film 23 and the first interlayer insulating film (first inorganic insulating film) 25. In other words, in a similar manner to Embodiment 1, the array substrate 111b of the present embodiment has the protective film 31 formed on the semiconductor film 23, but in the case of the present embodiment, the area in which the protective film 31 is formed is set to be wider than in Embodiment 1. In addition, the protective film 31 is also formed of silicon oxide (SiOx, in which x=2, for example) in a similar manner to Embodiment 2.
In the case of the present embodiment, the protective film 31 is provided so as to cover a portion of the surface of the semiconductor film 23 that is not in contact with the source electrode 18c or the drain electrode 18d. For convenience of explanation, the portion of the source electrode 18c that contacts the semiconductor film 23 is referred to as a contact portion 18c1, and the portion of the drain electrode 18d that contacts the semiconductor film 23 is referred to as a contact portion 18d1. The protective film 31 has an opening 31a to make the contact portion 18c1 contact the semiconductor film 23 and has an opening 31b to make the contact portion 18d1 contact the semiconductor film 23. In the case of the present embodiment, the protective film 31 is formed so as to cover the entire gate insulating film (second electrode side insulating film) 24 (excluding portions other than openings 31a and 31b). In a similar manner to Embodiment 2, the protective film 31 of the present embodiment is also formed by performing photolithography, etching, resist removal and cleaning, and the like to the silicon oxide formed by the plasma CVD method or the like.
A source electrode (fourth electrode) 18c and a drain electrode (fifth electrode) 18d form a pair over the semiconductor film 23 on the array substrate 111b of the present embodiment such that the electrodes 18c and 18d face each other with the channel region 18b therebetween. The electrodes 18c and 18d respectively have the contact portion 18c1 and 18d1 that come into direct contact with the surface of the semiconductor film 23. In addition, the protective film 31 formed on the array substrate 111b so as to cover a portion of the surface of the semiconductor film 23 other than the portion in contact with the contact portion 18c1 and 18d1. In this manner, the protective film 31 more reliably protects the semiconductor film 23 (in particular, channel region 18b) from moisture and the like by covering the surface of the semiconductor film 23 that does not contact the contact portions 18c1 and 38d1. In addition, the semiconductor film 23 having the channel region 18b can be protected from moisture and the like even when the source electrode 18c and the drain electrode 18d are being formed.
By having an organic insulating film 26 with an opening (first opening) 26a in a location that overlaps the channel region 18b of the semiconductor film 23 protected by the protective film 31, the electrical characteristics of the semiconductor film 23 of the array substrate 111b of the present embodiment is suppressed from degrading caused by foreign materials such as moisture entering the channel region 18b of the semiconductor film 23 through the organic insulating film 26.
Next, Embodiment 3 of the present invention will be described using
The basic structure of the array substrate 211B of the present embodiment is similar to the structure in Embodiment 1. However, for the array substrate 211b of the present embodiment, a gate electrode (second electrode) 118a having TFTs 118 is configured to be narrower in the X axis direction (alignment direction of gate wiring line 20) than the gate electrode 18a of Embodiment 1. As a result, both edge portions of the semiconductor film 123 in the X axis direction (alignment direction of gate wiring line 20) overlaps the gate electrode 118a through a gate insulating film 24 while extending beyond the gate electrode 118a in a plan view. In addition, as shown in
The array substrate 211b of the present embodiment is similar to Embodiment 1 and has a protective film 131 to protect the channel region 118b of the semiconductor film 123. This protective film 131 is formed of silicon oxide (SiOx, x=1, for example) in a similar manner to the protective film 31 of Embodiment 1. In short, the array substrate 211b of the present embodiment uses a TFT 118 instead of the TFT 18 of Embodiment 1.
By having an organic insulating film 26 with an opening (first opening) 26a in a location that overlaps the channel region 118b of the semiconductor film 123 protected by the protective film 131, the electrical characteristics of the semiconductor film of the array substrate 211b of the present embodiment is suppressed from degrading caused by foreign materials such as moisture entering the channel region 118b of the semiconductor film 123 through the organic insulating film 26.
Also, if the opening (first opening) 26a of the array substrate 211b of the present embodiment fits inside the protective film 131 in a plan view, then, because foreign materials such as moisture that moves towards the semiconductor film 123 through the organic insulating film 26 is farther away from the protective film 131, the moisture and the like is suppressed from entering the semiconductor film 123 from the periphery of the protective film 131 by moving along the surface of the protective film 131.
Next, Embodiment 4 of the present invention will be explained with reference to
However, the array substrate 311b of the present embodiment is different from Embodiment 3 in that the array substrate 311b has a protective film 131 disposed between a semiconductor film 123 and a first interlayer insulating film (first inorganic insulating film) 25 such that the protective film 131 covers substantially the entire surface of the semiconductor film 123. In other words, the array substrate 311b of Embodiment 4 has the protective film 131 formed on the semiconductor film 123 in a similar manner to Embodiment 3, but in the case of the present embodiment, the area in which the protective film 131 is formed is configured to be wider than in Embodiment 3.
In the present embodiment, the protective film 131 is formed so as to cover a portion of the surface of the semiconductor film 123 that is not in contact with the source electrode 118c or the drain electrode 118d. For convenience of explanation, the portion of the source electrode 118c that contacts the semiconductor film 123 is referred to as a contact portion 118c1, and the portion of the drain electrode 118d that contacts the semiconductor film 123 is referred to as a contact portion 118d1. The protective film 131 has an opening 131a to make the contact portion 118c1 contact the semiconductor film 123 and has an opening 131b to make the contact portion 118d1 contact the semiconductor film 123. In the case of the present embodiment, the protective film 131 is formed so as to cover the entire gate insulating film (second electrode side insulating film) 24 (excluding portions other than openings 131a and 131b). In a similar manner to Embodiment 2 and the like, the protective film 131 of the present embodiment is also formed by performing photolithography, etching, resist removal and cleaning, and the like on the silicon oxide film formed by a plasma CVD method or the like.
By having an organic insulating film 26 with an opening (first opening) 26a in a location that overlaps the channel region 118b of the semiconductor film 123 protected by the protective film 131, the electrical characteristics of the semiconductor film of the array substrate 311b of the present embodiment is suppressed from degrading caused by foreign materials such as moisture entering the channel region 118b of the semiconductor film 123 through the organic insulating film 26.
The present invention is not limited to the embodiments shown in the drawings and described above, and the following embodiments are also included in the technical scope of the present invention, for example.
(1) In the respective embodiments above, an example of an array substrate for an FFS mode liquid crystal display device was shown, but in other embodiments, as long as the objective of the present invention is not hindered, an array substrate for a liquid crystal display device using other operation modes such as an IPS (in-plane switching) mode liquid crystal display device or a VA (vertical alignment) mode liquid crystal display device may be used.
(2) In the respective embodiments above, the common electrode was formed so as to be in the opening (first opening) of the organic insulating film, but in other embodiments, the common electrode (third electrode) may be formed in a location that does not overlap the channel region of the TFT.
(3) In the respective embodiments above, the third electrode is used as a common electrode of the liquid crystal display device (array substrate), but in other embodiments, the third electrode may be used as a capacitance electrode formed of a transparent conductive film in the VA mode, for example.
(4) In the respective embodiments above, the first interlayer insulating film (first inorganic insulating film) is formed of silicon oxide (SiOx), but in other embodiments, other inorganic materials such as silicon nitride (SiNx), silicon oxynitride (SiNxOy, x>y), and silicon oxynitride (SiOxNy, y>x) may be used.
(5) In the respective embodiments above, the second interlayer insulating film (second inorganic insulating film) is formed of silicon oxide (SiOx), but in other embodiments, other inorganic materials such as silicon nitride (SiNx), silicon oxynitride (SiNxOy, x>y), and silicon oxynitride (SiOxNy, y>x) may be used.
(6) In the respective embodiments above, the first metal film used for the gate wiring line, the gate electrode, and the like, and the second metal film used to form the source wiring line, the source electrode, the drain electrode, and the like were both layered structures having two layers (two types) of metal films, but in other embodiments, these metal films may be formed of one layer (one type), for example.
(7) In the respective embodiments above, the first metal film and the second metal film both have a bottom layer side that is a titanium (Ti) film, and a copper (Cu) film is formed on the titanium (Ti) film as the top layer side. In other embodiments, the bottom layer side may be formed of a metal film other than a titanium (Ti) film such as molybdenum (Mo), molybdenum nitride (MoN), titanium nitride (TiN), tungsten (W), niobium (Nb), tantalum (Ta), molybdenum titanium (MoTi), and molybdenum tungsten (MoW).
(8) In the respective embodiments above, the gate insulating film (second electrode side insulating film) had a two layer structure, but in other embodiments, the gate insulating film may have one layer or more than two layers. In addition, the gate insulating film (second electrode side insulating film) may be formed of materials other than silicon nitride (SiNx) and silicon oxide (SiOx) such as silicon nitride (SiNx), silicon oxynitride (SiNxOy, x>y), silicon oxynitride (SiOxNy, y>x), and the like.
(9) In the respective embodiments above, a capacitance wiring line was not provided on the array substrate, but in other embodiments, a capacitance wiring line may be provided as necessary.
(10) In the respective embodiments above, the opening (contact hole) for connecting the pixel electrode to the drain electrode was provided in a location that is relatively far from the TFT, but in other embodiments, the opening may be provided in a location closer to the TFT than in the respective embodiments above.
(11) In the respective embodiments above, a transparent inorganic conductive film such as ITO was used as a material of the pixel electrode, but in other embodiments (for reflective liquid crystal display devices, for example), a conductive film such as titanium, tungsten, nickel, gold, platinum, silver, aluminum, magnesium, calcium, lithium, and alloys of these may be used, for example.
(12) In the respective embodiments mentioned above, an array substrate used as a semiconductor device of a liquid crystal panel was shown as an example, but in other embodiments, the semiconductor device may be used in an organic EL device, inorganic EL device, electrophoretic device, or the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-221198 | Oct 2012 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/076497 | 9/30/2013 | WO | 00 |
