Detailed description will be given below on the best aspect of the embodiment of the present invention.
In
An insulator film INS2 is formed to cover the source-drain electrodes SD, and a protective insulator film PAS is arranged on the uppermost layer. In the pixel area shown in
As shown in
By designing the thin-film transistor and the storage capacitor in the structure as described above, the number of the processes can be reduced by one process each in the photolithographic process and ion implantation process. As a result, the active matrix substrate of the image display unit can be manufactured in shorter time and at lower cost. By using this active matrix substrate, an image display unit to give higher image quality can be manufactured at lower cost.
Next, description will be given on a method for manufacturing the active matrix substrate of the Embodiment 1 of the image display unit of the present invention as explained in connection with
First, on a glass substrate SUB, which is a transparent insulator substrate, a silicon oxide film SiO2 is deposited with the thickness of 100 nm as an underlying film BUF. (A silicon nitride film SiN may be deposited in the same thickness under it and may be used as a laminated underlying film.) On the underlying film BUF, an amorphous silicon layer (a-Si) is deposited in thickness of 50 nm by the plasma CVD method. XeCl excimer layer is projected to the amorphous silicon layer to crystallize it, and a polysilicon film (p-Si) PSI is prepared. By a first photolithographic process and dry etching, the polysilicon film PSI is formed in island-like shape by patterning. On it, a silicon oxide film is deposited in thickness of 100 nm as the gate insulator film GI by the plasma CVD method.
For threshold adjustment of NMOSTFT, boron ions are implanted by low density ion implantation on the entire surface with implantation energy of 30 keV and implantation quantity of 1×1012/cm2 (formation of LDP region) (
As the bottom layer metal (lower gate layer) GMB of the gate electrode GT, titanium (Ti) is deposited in thickness of 30 nm. As the top layer metal (upper gate layer) GMT, molybdenum-tungsten (MoW) is continuously deposited in thickness of 150 nm by the sputtering method. As the material of the bottom layer metal GMB, titanium nitride (TiN) or other adequate metal may be used instead of titanium. The thickness of the bottom layer metal GMB is preferably thinner because it is used as a through-film at the time of ion implantation. However, if it is too thin, disconnection of the line or the increase of resistance may occur, and the thickness is preferably in the range of about 20-60 nm. If the bottom layer metal GMB is thin, the light partially passes through it, and brighter pixel can be obtained. By using a transparent metal such as ITO (indium tin oxide) or ZnO as the bottom layer metal, the light can pass through much easier. As the top layer metal GMT, molybdenum (Mo), tungsten (W), chromium (Cr) or other type of metal may be used instead of MoW. However, a material to give adequate selection ratio at the time of etching of the top layer metal GMT should be used as the bottom layer metal GMB. The thickness of the top layer metal GMT is preferably in the range of 120-200 nm. By the second photolithographic process and wet etching, the top layer metal GMT is processed. In this case, it is processed so that side etching of 1 μm can be made for the subsequent formation of LDD region. The width of side etching is preferably in the range of 0.5-2 μm. The storage capacitor Cst should be laid out so that the top layer metal GMT is removed. In so doing, ion implantation of the bottom electrode of the storage capacitor can be performed after the preparation of the gate electrode. Also, the storage line (storage capacitor line) CL is left as it is laminated to prevent the increase of resistance.
Leaving the resist remaining as it is, high density n-type ion implantation is performed with phosphorus ions of 8×1014 cm−2 at 75 keV (formation of HDN region). As a result, ion implantation can be performed on the source and the drain. At the same time, ions can be implanted to the bottom electrode of the storage capacitor Cst. That is, one process can be reduced in the ion implantation process. To alleviate electric field at the end of the drain, phosphorus ion implantation with low implantation quantity is carried out with 1×1013/cm−2 at 80 keV, and LDD region is prepared. The ion implantation for LDD region may be carried out after the processing of the next bottom layer metal GMB (
By the third photolithographic process and dry etching, the bottom layer metal GMB is processed. In this case, the NMOSTFT and the PMOSTFT are processed by using the top layer metal GMT of the gate electrode GT as a mask, and the storage capacitor Cst is processed by using the resist RST as a mask. The bottom layer metal GMB may be processed by wet etching (
By the fourth photolithographic process, the NMOSTFT and the storage capacitor Cst are covered with the resist RST, and high density p-type ion implantation is performed with boron ions of 1.5×1015 cm−1 at 30 keV, and ion implantation is carried out on the source-drain of the PMOSTFT (
Leaving the resist RST remaining as it is, the top layer metal GMT of the PMOSTFT is removed. The gate electrode of the PMOSTFT has the bottom layer metal GMB only. The contact region and the line region are left under laminated condition. Then, by leaving the resist RST remaining as it is, phosphorus ions of 1×1012 cm−2 are implanted at 80 keV via the bottom layer metal GMB for threshold adjustment of MOSTFT (formation of LDN region).
As a result, one process in the photolithographic process can be reduced (
As the interlayer insulator film INS1, a SiO2 film is deposited by the plasma CVD method. By the fifth photolithographic process and wet etching, a contact hole is formed. A laminated film of MoW/Al/MoW is deposited as a wiring layer by the sputtering method. By the sixth photolithographic process and wet etching, the source-drain SD and the wiring are prepared (
As the insulator layer INS2, a SiN film is deposited by the plasma CVD method. Further, a photosensitive organic film is coated as the protective insulator film PAS. By the seventh photolithographic process and etching, a contact hole is formed. As the transparent metal for the pixel electrode, ITO film is deposited by the sputtering method. By the eighth photolithographic process and wet etching, the pixel electrode PX is prepared (
By the manufacturing process as described above, one process each can be reduced in the photolithographic process, which requires the longest time, and in implantation process, and the active matrix substrate can be manufactured in shorter time and at lower cost. Because the light passes through the storage capacitor, an image display unit to give brighter image can be obtained.
In the active matrix substrate in the Embodiment 1 as described above, the bottom electrode to make up the storage capacitor is made of n-type polysilicon. In the active matrix substrate in the Embodiment 2 of the image display unit of the present invention, the storage capacitor has the bottom electrode of n-type polysilicon and the bottom electrode of p-type polysilicon.
Now, referring to
First, by the same manufacturing process as the process in
Next, when the NMOSTFT and the storage capacitor are covered by the resist in the fourth photolithographic process, an opening is formed on a region where the bottom electrode of p-type polysilicon is to be made. High density p-type ion implantation is performed by using boron ions of 1.5×1015 cm−2 at 30 keV. Ion implantation is performed on the source-drain of the PMOSTFT, and HDP region is prepared. At the same time, doping is carried out on the bottom electrode GMB of the storage capacitor Cst (ion implantation) (
Then, in the same manner as the manufacturing process in the Embodiment 1, by leaving the resist RST remaining as it is, the top layer metal GMT of the PMOSTFT is removed. The gate electrode of the PMOSTFT has now only the bottom layer metal GMB. The contact region and the line region are left under laminated condition. By leaving the resist RST remaining as it is, phosphorus ions are implanted with 1×1012 cm−2 at 80 keV via the bottom layer metal GMB for threshold adjustment of the PMOSTFT. As a result, one process can be reduced in the photolithographic process (
As the interlayer insulator film INS1, a SiO2 film is prepared by the plasma CVD method. By the fifth photolithographic process and wet etching, a contact hole is formed. As a wiring layer, a laminated film of MoW/Al/MoW is deposited by the sputtering method. By the sixth photolithographic process and wet etching, the source-drain SD and the wiring are prepared (
As the insulator layer INS2, a SiN film is deposited by the plasma CVD method. Further, a photosensitive organic film is coated as a protective insulator film PAS. By the seventh photolithographic process and etching, a contact hole is formed. As a transparent metal for pixel electrode, ITO film is deposited by the sputtering method. By the eighth photolithographic process and wet etching, the pixel electrode PX is prepared (
In the manufacturing process as described above, one process each can be reduced in the photolithographic process requiring the longest time and in the implantation process, and the active matrix substrate can be produced in shorter time and at lower cost. Because the light passes through the storage capacitor, an image display unit to provide brighter image can be obtained.
In the active matrix substrate in the Embodiment 1, the NMOSTFT has LDD structure. In the Embodiment 3, the NMOSTFT of LDD structure and GOLD (Gate Overlapped LDD) structure are adopted. Referring to
The GOLD structure has higher hot carrier tolerance (endurance) than the LDD structure, while it is higher in leakage current and adding capacity than the LDD structure.
In this respect, the LDD structure is adopted for the NMOSTFT of the pixel area where lower leakage current and lower adding capacity are required, and the GOLD structure is adopted for the NMOSTFT of peripheral circuit region where hot carrier is most likely to occur.
First, by the same manufacturing process used in
Next, in the photolithographic process for the processing of the lower gate for the NMOSTFT of the circuit region, resist patterning is prepared with a width by 1 μm wider than the upper gate (
In the processes similar to those of the Embodiment 1, by the fourth photolithographic process, the NMOSTFT and the storage capacitor Cst are covered by the resist RST. High density p-type ion implantation is performed with boron ions of 1.5×1015 cm−2 at 30 keV, and ions are implanted in the source-drain of the PMOSTFT (formation of HDP region) (
By leaving the resist remaining as it is, the top layer metal GMT of the PMOSTFT is removed. The gate electrode of the PMOSTFT has only the bottom layer metal GMB. The contact region and the wiring region are left under laminated condition. Next, by leaving the resist RST remaining as it is, phosphorus ions of 1×1012 cm−2 are implanted via the bottom layer metal GMB at 80 keV for threshold adjustment of the PMOSTFT. As a result, one process can be reduced in the photolithographic process (
As the interlayer insulator film INS1, a SiO2 film is deposited by the plasma CVD method. By the fifth photolithographic process and wet etching, a contact hole is formed. As the wiring layer, a laminated film of MoW/Al/MoW is deposited by the sputtering method. By the sixth photolithographic process and wet etching, the source-drain SD and the wiring are prepared (
As the insulator film INS2, a SiN film is deposited by the plasma CVD method. Further, as the protective insulator film PAS, a photosensitive organic film is coated. By the seventh photolithographic process and etching, a contact hole is formed. As the transparent metal for pixel electrode, ITO film is deposited by the sputtering method. By the eighth photolithographic process and wet etching, the pixel electrode PX is prepared (
In the Embodiment 3, the NMOSTFT of the LDD structure and the NMOSTFT of the GOLD structure can be obtained at the same time without increasing the number of processes. Hot carrier tolerance (endurance) of the NMOSTFT of the peripheral circuit region can be improved. Without decreasing image display performance, an image display unit with longer service life can be manufactured.
In
The pixel PXL comprises the NMOSTFT, the PMOSTFT, the storage capacitor Cst, an organic EL element OLE, and a pixel electrode PX. It also comprises a signal line SL, a gate line GL, an on-off switch line SWL, and a voltage (power source) line VL. The pixel PXL is selected by a scanning signal sent via a gate line GL from a gate line driving circuit GDR, and display data sent from a data line driving circuit DDR via a data line DL is maintained at the storage capacitor Cst. The PMOSTFT is turned on by an on-off control signal sent via the on-off switch line SWL, and electric current to match the size of the display data maintained at the storage capacitor Cst is delivered from the power source line VL to the organic EL element OLE. The organic EL element OLE emits a light to match the value of the flowing electric current.
The storage capacitor Cst uses high density n-type polysilicon layer and the gate electrode layer as the bottom electrode and the top electrode. The thin-film transistor TFT of the gate line driving circuit of the peripheral circuit includes NMOSTFT and PMOSTFT. The procedure of the processing of the active matrix substrate of the organic EL display unit is the same as the procedure in the Embodiment 1 as explained in connection with
In case of the active matrix substrate of the organic EL display unit, after the processes as described above, a SiN film INS3 is deposited by the plasma CVD method as a protective insulator film. Then, the protective insulator film above the pixel electrode is removed by photolithographic process, and an opening is formed (AP). By mask deposition method, an organic EL layer is deposited. Further, a common electrode made of aluminum, for instance, is prepared. Therefore, this organic EL display unit is of bottom emission type to emit the light on the active matrix substrate. In case of top emission type, by which the light is emitted on opposite side of the active matrix substrate, a reflective metal film such as aluminum is used as the pixel electrode, and a transparent electrode such as ITO is used as the common electrode.
By the Embodiment 4, one process each can be reduced in the photolithographic process requiring the longest time and in the implantation process, and an active matrix substrate for the organic EL display unit can be manufactured in shorter time and at lower cost.
The insulating substrate in the Embodiment 1 to the Embodiment 4 as described above may be made of quartz or plastics instead of glass. When a laminated film of SiO2 film and SiN film is used instead of the SiO2 film as the underlying film layer, adverse effect of unnecessary ions on the liquid crystal layer or the like can be prevented by the SiN film, which has the effects to suppress the diffusion of impurities.
Also, the method for crystallizing the amorphous silicon is not limited to the excimer laser annealing. Solid-state laser annealing or solid-state growth by heat annealing or a combination of these may be used. The semiconductor film may be microcrystal silicon. Or, compounds of Si and Ge or other types of semiconductor of oxide already known may be used.
On the active matrix substrate SUB1 with an arrangement of one of the Embodiment 1 to 3 as described above, a liquid crystal orientation film layer is prepared, and a force to control orientation is applied on it by the means such as rubbing. After a sealing agent is put on the periphery of a pixel area AR, a counter substrate SUB2 with an orientation film layer formed on it is placed at opposed position with a certain gap. A liquid crystal is sealed into this gap, and sealing site of the sealing agent is closed with a sealing material. On front and rear surfaces of a liquid crystal cell PNL thus prepared, polarizers POLL and POL2 are laminated. A liquid crystal display unit is manufactured by mounting a backlight or the like on it, which comprises a light guide plate GLB and a cold cathode fluorescent lamp CFL. To the driving circuit around the liquid crystal cell, data and timing signals are sent via flexible printed boards FPC1 and FPC2. On the component referred by the reference symbol PCB, a timing controller or the like is mounted, which converts a display signal inputted from the external signal source to a signal mode to display on the liquid crystal display unit between the external signal source and each of the flexible printed boards FPC1 and FPC2.
This organic EL display unit supplies a display signal from an external signal source to the driving circuit regions DDR and GDR via the printed board PLB. An interface circuit chip CTL is mounted on the printed board PLB. This is integrated with the shield frame SHD, i.e. an upper case, and with a lower case CAS to make up the organic EL display unit.
Number | Date | Country | Kind |
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2006-286235 | Oct 2006 | JP | national |