Patent Application
20090278236
This application claims priority to Japanese patent application serial No. 2008-122513, filed on May 8, 2008, the entire content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a semiconductor device, a wafer structure and a method for fabricating the semiconductor device and more specifically to the semiconductor device, the wafer structure and the method for fabricating the semiconductor device using compound semiconductors.
2. Description of the Photo-Resist Related Art
Conventionally, a WCSP (Wafer-Level Chip Size Packaging) technique is used in general in fabricating semiconductor devices to accommodate to semiconductor devices whose size and weight are reduced. The WCSP separates the semiconductor devices into individual chips by dicing the wafer after forming rewiring layers and passivation layers in a state of the wafer. In dicing the wafer, a trench whose width is wider than a dicing blade is formed along a scribing region that is a part to be cut and a bottom of the trench is cut by a dicer in an array direction as disclosed in Japanese Patent Application Laid-open No. Hei. 9-330891 for example. A silicon oxide film is used in general as a mask in forming the trench due to its easiness in forming the film and its cost.
In addition, semiconductor elements using various compound semiconductors such as III-V group semiconductors and II-VI group semiconductors are being developed lately because it has become possible to form various semiconductor elements and because it is required to operate and drive semiconductors more quickly at low voltage.
While the compound semiconductors described above are used to form semiconductor elements such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a HEMT (High Electron Mobility Transistor) and a SBD (Schottky Barrier Diode) for example, a metal film such as aluminum (Al) is normally used as an electrode material such as a gate electrode and others due to its low fabrication cost and its easiness of the fabrication process. However, because the metal film of this sort is soluble in etchant such as hydrofluoric acid used in etching a silicon oxide film used as a mask, the metal film causes problems that it complicates a fabrication process and limits a degree of freedom in selecting materials if the trench to be cut is formed in the scribing region after forming the various electrodes.
The prior art fabrication method is thus arranged to form the trench in the scribing region before forming the various electrodes from the reasons as described above. However, if the process (referred to as a microfabrication process hereinafter) that requires such a relatively fine fabrication process of forming the various electrodes is placed behind the process of forming the trench, there exists the trench whose width is larger than a thickness of the dicing blade or a diameter of a spot of a laser cutter for example at the time of the microfabrication process. This causes a problem that a photo-resist used in photolithography in the microfabrication process cannot be formed uniformly.
In view of the problem described above, the present invention seeks to provide a semiconductor device, a wafer structure and a method for fabricating the semiconductor device that allow the photo-resist used in the photolithography in the microfabrication process to be uniformly formed even if the trench for separating the semiconductor devices is created before the microfabrication process.
Accordingly, the invention provides a semiconductor device in which one or more semiconductor elements are formed in an element forming region on one or more compound semiconductor layers formed on a predetermined substrate, including a trench that divides the compound semiconductor layers is formed between a cut surface caused by separation and a side surface of the element forming region of the compound semiconductor layers.
Preferably, the trench is formed at least from the compound semiconductor layer to the predetermined substrate.
Preferably, the compound semiconductor contains at least one of GaN, AlGaN, BAlGaN, InGaN, GaAs, InP and SiGe.
Preferably, the semiconductor element contains at least one of a MOSFET, a HEMT and a SBD.
A wafer structure having one or more compound semiconductor layers including a plurality of element forming regions and scribing regions disposed between the element forming regions includes two trenches formed in the scribing regions that divide the neighboring element forming regions in the compound semiconductor layers.
A method for fabricating a semiconductor device of the invention includes steps of forming one or more compound semiconductor layers containing a plurality of element forming regions on a predetermined substrate, forming two trenches that divide the element forming regions in the compound semiconductor layers and forming semiconductor elements in the divided element forming regions.
Preferably, the step of forming the elements in the method includes a step of forming electrodes.
Preferably, the trenches are formed so as to reach the predetermined substrate in the trench forming step of the method.
The method further includes a step of separating the semiconductor devices into individual chips by cutting a convex portion located between the two trenches and a width of a top surface of the convex portion is larger than a thickness of a dicing blade or a spot diameter of a laser cutter used in the separating step.
Preferably, the trench is formed in the trench forming step of the method by means of etching.
Preferably, the compound semiconductor layer in the method contains at least one of GaN, AlGaN, BAlGaN, InGaN, GaAs, InP and SiGe.
Best modes for carrying out the invention will be explained in detail below with reference to the drawings. It is noted that the modes described below should not be construed as what limit the invention. Still more, each drawing merely schematically shows shapes, sizes and positional relationships of respective parts of a device to a degree that allows contents of the invention to be understood, so that the invention is not limited by the shapes, sizes and positional relationships illustrated in each drawing. Further, a part of hatching in a cross-section is omitted in each drawing in order to clearly show a structure of the device. In addition, numerical values described later are merely preferable exemplary values of the invention, so that the invention is not limited by the exemplified numerical values.
A semiconductor device 100 of a first embodiment of the invention will be explained below in detail with reference to the drawings. It is noted that the semiconductor device 100 in which one or more MOSFETs 100A are formed as semiconductor elements will be exemplified in the present embodiment.
(Structure)
As shown in
A scribing region SR that is a part to be cut in separating each semiconductor device 100 is set between the vertically or horizontally neighboring element forming regions AR1 and two parallel trenches TR are formed along a direction in which the scribing region SR extends. There exists a mesa-like convex portion 120 that extends along the direction in which the scribing region SR extends between the two trenches TR. The present embodiment separates the respective semiconductor devices 100 into individual chips by cutting the convex portion 120 between the two trenches TR by using a dicing blade or a laser cutter for example.
As shown in
The wafer 1 of the present embodiment before separating the semiconductor devices into individual chips has the two trenches TR formed along the scribing region SR between the neighboring element forming regions AR1 and the convex portion 120 between the trenches TR as described above. The convex portion 120 between the trenches TR is cut along the direction in which it extends in separating the semiconductor devices. Then, a width Wconv of a top surface of the convex portion 120 is set to be wider than a width to be removed during cutting that is determined by a thickness of the dicing blade or a spot diameter of the laser cutter for example. When the thickness of the dicing blade is around 100 μm for example, the width Wconv of the top surface of the convex portion 120 is set to be around 200 μm or more. It allows physical or thermal damages otherwise given to the element forming region AR1 during cutting to be reduced. However, the invention is not limited to such a case and the width Wconv of the top surface of the convex portion 120 may be set to be in the same range with or less than the thickness of the dicing blade or the spot diameter of the laser cutter. It allows an area to be used as the scribing region SR on the wafer 1 to be reduced, so that it becomes possible to increase an effective area usable as the element forming region AR1. It is noted that the mesa-like convex portion 120 formed between the two trenches TR includes a convex portion 101b that is an upper layer part of the silicon substrate 101 and part of various films 101a, 102a, 103a, 104a and 105a formed in fabricating the semiconductor element described above for example as shown in
Because the width Wconv of the top surface of the convex portion 120 is set to be wider than the thickness of the dicing blade or the spot diameter of the laser cutter used in separating the semiconductor devices in the present embodiment as described above, it is not necessary to widen a width WTR of each trench TR more than the thickness of the dicing blade or the spot diameter of the laser cutter. As a result, it becomes possible to fully narrow down the width WTR of the trench TR around to or less than 10 μm. It becomes also possible to uniformly form the photo-resist used in the photolithographic process in the microfabrication process by narrowing down the width as described above even if the step of forming the trench TR is placed before the microfabrication process. Still more, because it becomes unnecessary to place the step of forming the trench TR after the microfabrication process by this arrangement, it is also possible to avoid the fabrication process from being complicated.
Still more, the trench TR is formed down to an upper layer part of the silicon substrate 101 for example in the present embodiment. This structure allows the trench TR to function as a trench for separating the elements between the semiconductor devices 100 in the present embodiment. A depth of the trench may be around 9 μm from a top surface of the passivation film 111 for example. However, although the trench TR reaching the upper layer part of the silicon substrate 101 is exemplified in the present embodiment, the invention is not limited to that and it will do as long as the trench TR from the top of the p-type semiconductor layer 103 is formed along a cut surface (see a side surface S2 in
Still more, the trench TR as described above may be formed by anisotropic dry etching using chlorine gas for example in the present embodiment. Therefore, a side surface of the trench TR, i.e., a side surface S1 of the element forming region AR1, is a surface having less irregularities and less physical and thermal damages as compared to the surface (hereinafter referred to a dicer cut surface) created by using the dicing blade or the laser cutter for example. This structure allows a leak current otherwise leaked to the substrate (the silicon substrate 101 in the present embodiment) via the side surface S1 of the element forming region AR1 to be reduced, so that it becomes possible to realize the semiconductor device 100 having excellent characteristics by the present embodiment.
An interlayer insulating film 109 having contact holes for making electrical connection with the semiconductor elements is formed on the silicon substrate 101 on which the semiconductor elements, the trench TR and the convex portion 120 are formed as described above. It is noted that an inside of the trench TR and the convex portion 120 may be covered by an insulating film 106a formed in the same time when the gate insulating film 106 is formed for example as shown in
Various substrates such as a sapphire substrate for example may be applied as the substrate described above beside the silicon (111) substrate 101. The buffer layer 102 on the silicon substrate 101 is a layer for buffering an interaction caused by characteristic differences of the p-type semiconductor layer 103 to be grown above the buffer layer 102 and the silicon substrate 101 and for improving joint strength of the both layers. The buffer layer 102 as described above may be formed by forming an AlN (aluminum nitride) layer whose thickness is around 50 nm on the silicon substrate 101 and by laminating 20 to 80 layers of layered films each composed of a GaN layer whose thickness is around 5 to 100 nm for example and an AlN layer whose thickness is around 1 to 10 nm for example on the AlN layer previously formed. However, the invention is not limited to this structure and may be variously modified depending on materials and others of the semiconductor layer (the p-type semiconductor layer 103 in the present embodiment) formed on the buffer layer 102.
The p-type semiconductor layer 103 on the buffer layer 102 contains p-type impurities for example and forms a channel during operation as described above. The p-type semiconductor layer 103 described above may be formed by using various semiconductors such as III group nitride semiconductors like GaN, AlGaN, BAlGaN and InGaN and other compound semiconductors like GaAs, InP and SiGe. A case of forming the p-type semiconductor layer 103 by using the GaN layer will be illustrated in the present embodiment. Still more, a case of using magnesium (Mg) as the p-type impurity will be illustrated while setting its concentration (Mg concentration) at around 1×1017/cm3 for example in the present embodiment.
The carrier drifting layer 104 and the carrier supplying layer 105 on the p-type semiconductor layer 103 are layers that form a so-called HEMT structure and generate two-dimensional electron gas that may be utilized as carrier during the operation in the upper layer of the carrier drifting layer 104 near the interface by forming the hetero-junction interface as described above. In the present embodiment, an un-doped GaN (hereinafter referred to as un-GaN) layer for example is used as the carrier drifting layer 104 and an un-doped AlGaN (hereinafter referred to as un-AlGaN) layer for example is used as the carrier supplying layer 105. However, the invention is not limited to those layers and various compound semiconductor growth films capable of generating two-dimensional electron gas may be applied by forming the hetero-junction interface.
A part of the HEMT structure on the p-type semiconductor layer 103 (part of the carrier drifting layer 104 and the carrier supplying layer 105) is removed and the gate insulating film 106 and the gate electrode 107 are formed on the p-type semiconductor layer 103 in the removed part. This structure allows the MOSFET 100A of the present embodiment to have a MOS structure composed of the p-type semiconductor layer 103, the gate insulating film 106 and the gate electrode 107. In the present embodiment, a silicon oxide film for example is used for the gate insulating film 106 and a metal film having a deposited structure in which an aluminum (Al) film is sandwiched by upper and lower titanium (Ti) films for example is used for the gate electrode 107. However, the invention is not limited to them and the semiconductor element incorporated in the semiconductor device 100 may be a FET having a MIS (Metal Insulator Semiconductor) structure for example. Accordingly, various insulating films and conductive films may be used also for the gate insulating film 106 and the gate electrode 107.
The paired source and drain electrodes 108s and 108d are formed at two regions interposing the gate electrode 107 on the carrier supplying layer 105 as described above. In the present embodiment, a metal layer having a deposited structure composed of an underlying Ti film and an upper Al film for example for the source and drain electrodes 108s and 108d. However, the invention is not limited to them and those electrodes may be formed by using various conductors capable of ohmically junctioning with the carrier supplying layer 105 for example.
The interlayer insulating film 109 that covers the semiconductor elements may be formed by using insulating films such as a silicon oxide film for example. The metal layer 110 on the interlayer insulating film 109 and within the contact hole may be formed by using the metal film having the deposited structure composed of the Ti film and the Al film. Still more, the passivation film 111 covering them may be formed by using insulating films such as a silicon nitride film for example.
(Fabrication Method)
Next, a method for fabricating the semiconductor device 100 by the present embodiment will be explained in detail with reference to the drawings.
According to this method, a buffer layer 102A is formed on the silicon substrate 101 at first as shown in
Specifically, trimethyl aluminum (TMA) and ammonium (NH3) for example are introduced into a chamber of a MOCVD (Metal Organic Chemical Vapor Deposition) containing the silicon substrate 101 with flow rates of around 100 μmol/min and around 12 liters/min, respectively. Thereby, the AlN layer whose thickness is around 100 nm for example is epitaxially grown on the silicon substrate 101. Next, the GaN layer whose thickness is around 200 nm for example is epitaxially grown by introducing trimethyl gallium (TMG) and ammonium onto the grown AlN layer with flow rates of around 58 μmol/min and of around 12 liters/min, respectively. In succession, the AlN layer whose thickness is around 20 nm for example is epitaxially grown by introducing TMA and ammonium for example onto the grown GaN layer with the similar flow rates as described above. After that, the growth films each composed of the GaN layer whose thickness is around 200 nm and the AlN layer whose thickness is around 20 nm are superimposed by eight layers for example to form the buffer layer 102A having the growth structure whose total thickness from the undermost AlN layer is around 1860 nm for example on the silicon substrate 101.
Next, Bis(Cyclopentadienyl)Magnesium: CP2Mg) is introduced onto the buffer layer 102A beside the TMG and ammonium for example. Thereby, the GaN layer (p-GaN layer) 103A into which Mg is doped as the p-type impurity is epitaxially grown on the buffer layer 102A. It is noted that a thickness of the p-GaN layer 103A may be around 500 nm for example. Flow rates of the TMG and ammonium at this time may be around 19 μmol/min and 12 liters/min, respectively. A flow rate of the CP2Mg may be what achieves 1×1017/cm3 of Mg concentration in the grown p-GaN layer 103A. Where, the Mg concentration is a result measured by a second ion mass spectroscopy (SIMS) for example.
Next, the un-GaN layer 104A whose thickness is around 100 nm for example is epitaxially grown by introducing TMG and ammonium onto the p-GaN layer 103A with flow rates of around 19 μmol/min and of around 12 liters/min, respectively. In succession, the un-AlGaN layer 105A whose thickness is around 20 nm for example is epitaxially grown by introducing TMA, TMG and ammonium onto the un-GaN layer 104A with flow rates of around 125 μmol/min, 19 μmol/min and of 12 liters/min, respectively. It is noted that a composition of the un-AlGaN layer 105A may be AL0.25Ga0.75N for example. Growth temperature of each layer (the buffer layer 102A, the p-GaN layer 103A, the un-GaN layer 104A and the un-AlGaN layer 105A) in the abovementioned processes may be around 1050° C. for example.
After forming the growth laminate film composed of the buffer layer 102A, the p-GaN layer 103A, the un-GaN layer 104A and the un-AlGaN layer 105A on the silicon substrate 101 as described above, a part of the un-AlGaN layer 105A and the un-GaN layer 104A in the element forming region AR1 is removed by using photolithographic and etching technologies for example as shown in
Next, after removing the silicon oxide film M1 used as the mask, two parallel trenches TR are formed between the element forming regions AR1 as shown in
As a result of the process described above, the buffer layer 102A, the p-GaN layer 103A, the un-GaN layer 104A and the un-AlGaN layer 105A in the element forming region AR1 are shaped respectively as the buffer layer 102, the p-type semiconductor layer 103, the carrier drifting layer 104 and the carrier supplying layer 105 and the elements are separated between the element forming regions AR1. Still more, as a result of the process described above, the mesa-like convex portion 120 composed of the convex portion 101b that is the upper layer part of the silicon substrate 101, the buffer layer 102a that is a part of the buffer layer 102A, the p-GaN layer 103a that is a part of the p-GaN layer 103A, the un-GaN layer 104a that is a part of the un-GaN layer 104A and the un-AlGaN layer 105a that is a part of the un-AlGaN layer 105A is formed between the two trenches TR in each scribing region SR.
After forming the two trenches TR and the convex portion 120 in the scribing region SR as described above, the silicon oxide film M2 used as the mask is removed and a silicon oxide film whose thickness is around 60 nm for example and which covers the whole upper surface of the silicon substrate 101 on which the respective layers described above are formed is formed by using a CVD (Chemical Vapor Deposition) technique for example. In succession, the silicon oxide film is processed by using photolithographic and etching techniques to remove at least a part of the silicon oxide film on the carrier supplying layer 105 as shown in
Next, the source and drain electrodes 108s and 108d that ohmically contact with the carrier supplying layer 105 that is exposed by the aperture ap3 of the gate insulating film 106 are formed on the carrier supplying layer 105 as shown in
Next, a gate electrode 107 is formed on the gate insulating film 106 as shown in
After forming the semiconductor element containing the MOSFET 100A composed of the p-type semiconductor layer 103, the carrier drifting layer 104, the carrier supplying layer 105, the gate insulating film 106, the gate electrode 107, the source and drain electrodes 108s and 108d in the element forming region AR1 as described above, the interlayer insulating film 109 whose thickness is around 3000 nm for example and which cover the whole upper surface of the silicon substrate 101 on which the respective layers are formed is formed by depositing silicon oxide by using a CVD technique for example. In succession, the contact holes that expose each part of the source and drain electrodes 108s and 108d as well as that of the gate electrode 107 are created through the interlayer insulating film 109 by using the photolithographic and etching techniques. Next, the metal layer 110 including the upper layer wire on the interlayer insulating film 109 and the in-contact wire within the contact hole is formed as shown in
Next, the passivation film 111 whose thickness is around 800 nm for example is formed on the interlayer insulating film 109 and the metal layer 110 as shown in
Next, after pasting a dicing sheet DS having an adhesive surface for example on the back of the silicon substrate 101 on which the respective layers are formed and fixing it on a dicing table not shown, the convex portion 120 in the scribing region SR of the silicon substrate 101 is cut by using a dicing blade DB for example as shown in
The semiconductor device 100 after being separated has a convex portion 120a that is a part of the convex portion 120 around an outer edge and the trench TR formed between the convex portion 120a and the element forming region AR1 as shown in
It is noted that although the case of forming the trench TR on the top surface of the silicon substrate 101, i.e., on the element forming surface, has been illustrated in the embodiment described above, the invention is not limited to that and may be arranged so as to form the trench TR from the back of the silicon substrate 101 for example. In this case, the trench TR is formed so that it reaches at least to the carrier supplying layer 105 from the back of the silicon substrate 101.
Next, a semiconductor device 200 of the second embodiment of the invention will be explained in detail with reference to the drawings. It is noted that the semiconductor device 200 on which one or more HEMT 200A are formed as semiconductor elements will be exemplified in the present embodiment. It is also noted that in the explanation below, the same structures with those of the first embodiment will be denoted by the same reference numerals and their detailed explanation will be omitted.
(Structure)
A structure of a wafer 2, seen from its top, before the semiconductor devices 200 are separated into individual chips in the present embodiment is the same with the structure shown in
As it is apparent when
The gate electrode 207 is formed on the carrier supplying layer 205 and Schottky-contacts with it as described above. A metal film having a deposited structure composed of an underlying nickel (Ni) layer and an upper gold (Au) film for example may be used for the gate electrode 207. However, the invention is not limited to that and the gate electrode 207 may be formed by using various conductors capable of Schottky-contacting with the underlying carrier supplying layer 205 for example.
The carrier drifting layer 204 and the carrier supplying layer 205 may be formed by using the same material with the carrier traveling layer 104 and the carrier drifting layer 105 of the first embodiment of the invention, so that their detailed explanation will be omitted here.
(Fabrication Method)
Next, a method for fabricating the semiconductor device 200 of the present embodiment will be explained in detail with reference to the drawings.
According to this method, the buffer layer 102A, the p-GaN layer 103A, the un-GaN layer 104A and the un-AlGaN layer 105A are formed at first one after another on the silicon substrate 101 by using the same processes with those explained by using
Next, the two parallel trenches TR are formed between the element forming regions AR1 as shown in
Next, the source and drain electrodes 108s and 108d that ohmically contact with the carrier supplying layer 205 are formed on the carrier supplying layer 205 as shown in
Next, the gate electrode 207 is formed in the region interposed between the source and drain electrodes 108s and 108d on the carrier supplying layer 205 as shown in
After that, the interlayer insulating film 109, the passivation film 111 and the passivation film 111 are formed one after another by using the same processes with those explained by using
Even if the semiconductor device 200 is fabricated as described above by forming the trenches TR for separation before the microfabrication process in the same manner with the first embodiment, it becomes possible to uniformly form the photo-resist used in the photolithography in the microfabrication process. Still more, the side surface of the trench TR, i.e., the side surface S1 of the element forming region AR1 is a surface formed by etching with less irregularities and less physical and thermal damages than the surface cut by the dicer, so that it becomes possible to reduce a leak current otherwise leaked to the substrate (the silicon substrate 101 in the present embodiment) through the side surface S1 of the element forming region AR1 and to realize the semiconductor device 200 having the excellent characteristics.
Next, a semiconductor device 300 of a third embodiment of the invention will be explained in detail with reference to the drawings. It is noted that the semiconductor device 300 on which one or more SBDs 300A are formed as semiconductor elements will be exemplified in the present embodiment. It is also noted that the same or corresponding structures with those in the first or second embodiment will be denoted by the same reference numerals and their detailed explanation will be omitted here.
(Structure)
Skelton structures above a wafer 3 before separating into the individual semiconductor devices 300 of the present embodiment is the same with those shown in
As it is apparent when
The cathode electrode 308c is an electrode made of a metal film that ohmically contacts with the carrier supplying layer 205. A metal film having a deposited structure composed of an underlying Ti film and an upper Al film for example is used in the present embodiment. However, the invention is not limited to that and the cathode electrode 308c may be formed by using various conductors that are capable of ohmically contacting with the underlying carrier supplying layer 205.
The anode electrode 308a is an electrode made of a metal film that Schottky-contacts with the carrier supplying layer 205. A metal film having a deposited structure composed of an underlying Ni film and an upper Al film for example is used in the present embodiment. However, the invention is not limited to that and the anode electrode 308a may be formed by using various conductors that are capable of Schottky-contacting with the underlying carrier supplying layer 205.
(Fabrication Method)
A method for fabricating the semiconductor device 300 of the present embodiment will be explained in detail below with reference to the drawings.
In the method of the present embodiment, the buffer layer 102A, the p-GaN layer 103A, the un-GaN layer 104A and the un-AlGaN layer 105A are formed at first one after another on the silicon substrate 101 by using the same processes with those explained by using
Next, the two parallel trenches TR as shown in
Next, the cathode electrode 308c that ohmically contacts with the carrier supplying layer 205 is formed on the carrier supplying layer 205 as shown in
Next, an anode electrode 308a that Schottky-contacts with the carrier supplying layer 205 is formed on the carrier supplying layer 205 as shown in
After that, the interlayer insulating film 109, the passivation film 111 and the passivation film 111 are formed one after another by using the same processes with those explained by using
Even if the semiconductor device 300 is fabricated as described above by forming the trenches TR for separation before the microfabrication process in the same manner with the first or second embodiment, it becomes possible to uniformly form the photo-resist used in the photolithography in the microfabrication process. Still more, the side surface of the trench TR, i.e., the side surface S1 of the element forming region AR1 is a surface formed by etching with less irregularities and less physical and thermal damages than the surface cut by the dicer, so that it becomes possible to reduce a leak current otherwise leaked to the substrate (the silicon substrate 101 in the present embodiment) through the side surface S1 of the element forming region AR1 and to realize the semiconductor device 300 having the excellent characteristics.
Thus, the invention has the structure in which the trench whose width is relatively narrow may be formed between the separation surface and the element forming region, not the structure that requires a trench whose width is wider than the thickness of the dicing blade or the diameter of a laser spot across the whole scribing region, so that it becomes possible to realize the semiconductor device and the method for fabricating the wafer structure and the semiconductor device that allow the photo-resist used in the photolithography in the microfabrication process even if the trench for the separation is formed before the microfabrication process.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-122513 | May 2008 | JP | national |
