JP2008-016717A翻译.doc

PATENT ABSTRACTS OF JAPAN(11)Publication number : 2008-016717(43)Date of publication of application : 24.01.2008(51)Int.CI.8 H01L 21/20 2H01L 21/268 2H01L 21/336 2H01L 29/786 2(21)Application number : 2006-187963(71)Applicant : MITSUBISHI ELECTRIC CORP(22)Date of filing : 07.07.2006(72)Inventor : YURA SHINSUKESONO ATSUHIROOKAMOTO TATSUKISUGAHARA KAZUYUKIYAMAYOSHI ICHIJI(54) MANUFACTURING METHOD OF POLYCRYSTALLINE SILICON FILM(57)Abstract:PROBLEM TO BE SOLVED: To provide a method for manufacturing a polycrystalline silicon film by which uniformity can be improved in crystal grain size of the polycrystalline silicon film formed by laser annealing.SOLUTION: The polycrystalline silicon film is formed by crystallizing an amorphous silicon film of 60 nm or more in thickness which is formed on a substrate by laser annealing, whereby laser with wavelengths of 390 nm to 640 nm (YAG2 laser, for example) is applied in an atmosphere under an oxygen partial pressure of 2 Pa or less. In this case, an irradiation energy density (for example, within a range Rg of 0.366 to 0.378 J/cm2) of laser is selected so that the average crystal grain size of the polycrystalline silicon film formed by laser annealing may be within a range of 0.28 m0.03 m. The polycrystalline silicon film is manufactured from the amorphous silicon film by performing laser annealing at the selected irradiation energy density. In this way, the polycrystalline silicon film which exhibits a small standard deviation relative value of crystal grain size can be formed and the uniformity of its crystal grain size can be improved.CLAIM + DETAILED DESCRIPTION Claim(s) Claim 1 It is how to manufacture a polycrystalline silicon film, A process of forming an amorphous silicon film of not less than 60 nm of thickness on a substrate, A crystallization stage which crystallizes said amorphous silicon film and forms a polycrystalline silicon film by laser annealing which oxygen tension irradiates with laser with a wavelength of 390 nm - 640 nm in atmosphere of 2 Pa or less, A preparation, Said crystallization stage, A selection process of selecting irradiation energy density of laser which becomes within the limits whose mean particle diameter of a crystal of a polycrystalline silicon film formed of said laser annealing is 0.28micrometer*0.03micrometer, A manufacturing process which performs said laser annealing with irradiation energy density of laser selected at said selection process, and manufactures said polycrystalline silicon film, A manufacturing method of a *(ing) polycrystalline silicon film. Claim 2 In a manufacturing method of the polycrystalline silicon film according to claim 1, A specific process of specifying a lower limit of irradiation energy density of laser which unevenness of the shape of a muscle which met in the direction vertical to a scanning direction of laser on the surface of a polycrystalline silicon film formed of said laser annealing produces, It prepares for a pan, A manufacturing method of a polycrystalline silicon film selecting said irradiation energy density in said selection process in a range to a lower limit to 95% of the lower limits concerned of irradiation energy density of laser specified at said specific process. Claim 3 In a manufacturing method of the polycrystalline silicon film according to claim 1, A measuring process which measures intensity of the scattered light which irradiates with a predetermined light which contained visible light to each surface of a polycrystalline silicon film formed by performing said laser annealing, changing said irradiation energy density, and are scattered about on each surface concerned, It prepares for a pan, While specifying an extremum of 4 which graph-izes intensity of said scattered light to said irradiation energy density based on a measurement result obtained by said measuring process, and becomes order with said low irradiation energy density from the 1st maximal value, 1st minimal value, 2nd maximal value, and 2nd minimal value, A manufacturing method of a polycrystalline silicon film characterized by selecting said irradiation energy density from the range of *10 mJ/cm2 centering on irradiation energy density corresponding to said 1st minimal value in said selection process. Claim 4 In a manufacturing method of the polycrystalline silicon film according to claim 3, A manufacturing method of a polycrystalline silicon film, wherein said predetermined light is white light. Claim 5 It is how to manufacture a polycrystalline silicon film, A process of forming an amorphous silicon film of not less than 60 nm of thickness on a substrate, A crystallization stage which crystallizes said amorphous silicon film and forms a polycrystalline silicon film by laser annealing which oxygen tension irradiates with laser with a wavelength of 390 nm - 640 nm in atmosphere of 2 Pa or less, A measuring process which measures intensity of the scattered light which irradiates with a predetermined light which contained visible light to each surface of a polycrystalline silicon film formed by performing said laser annealing, changing irradiation energy density of said laser, and are scattered about on each surface concerned, A preparation, While specifying an extremum of 4 which graph-izes intensity of said scattered light to said irradiation energy density based on a measurement result obtained by said measuring process, and becomes order with said low irradiation energy density from the 1st maximal value, 1st minimal value, 2nd maximal value, and 2nd minimal value, Said crystallization stage, A manufacturing process which performs said laser annealing with irradiation energy density selected from the range of *10 mJ/cm2 centering on irradiation energy density corresponding to said 2nd minimal value, and manufactures said polycrystalline silicon film, A manufacturing method of a *(ing) polycrystalline silicon film. Detailed Description of the Invention Field of the Invention 0001 This invention relates to the method of irradiating an amorphous silicon film with laser and obtaining a polycrystalline silicon film. Background of the Invention 0002 Now, the picture element part of a liquid crystal panel or an organic electroluminescence (electro luminescence) panel Switching by the thin film transistor (TFT:Thin Film Transistor) on glass or the substrate made from synthetic quartz which was amorphous or was formed in the silicone film of polycrystal constitutes the picture. Although mainly installed outside independently now, if the driver circuit which drives a picture element transistor to this liquid crystal panel can be constituted simultaneously, a fast merit can be obtained in respect of the manufacturing cost of a liquid crystal panel or an organic EL panel, reliability, etc. Now, since the crystallinity of the silicone film which constitutes the active layer of TFT is bad, the performance of TFT represented by the mobility of a carrier is low, and production of the integrated circuit in which rapidity and highly efficient nature are demanded is difficult. In order to improve the crystallinity of a silicone film for the purpose of realizing TFT which has a carrier of high mobility, generally heat treatment (laser annealing) by laser radiation is performed. 0003 The relation between the crystallinity of a silicone film and the carrier mobility in TFT is explained as follows. Generally the silicone film obtained by carrying out laser annealing of the amorphous silicon film is a polycrystal. The crystal defect is carrying out localization to the grain boundary of the polycrystal, and this checks carrier movement of the active layer of TFT. Therefore, what is necessary is to lessen the number of times of crossing the grain boundary, while a carrier moves an active layer, and just to make crystal defect density small, in order to make carrier mobility in TFT high. A crystal grain diameter is large and the purpose of laser annealing has a crystal defect in the grain boundary in forming few polycrystalline silicon films. 0004 Next, the manufacturing method of the conventional TFT is explained. First, for example, silicon oxide is formed on a glass substrate by plasma CVD (Chemical Vapor Deposition: chemicals gaseous phase vacuum deposition). An amorphous silicon film is deposited by plasma CVD on this silicon oxide. Subsequently, the excimer laser (XeCl (wavelength: 308 nm) or Nd: The 2nd harmonics of an YAG laser (wavelength: 532 nm.) The following YAG2omega laser is called. It glares on an amorphous silicon film. The silicon which carried out melting crystallizes and a polycrystalline silicon film is formed as the portion with which this laser was irradiated carries out melting of the amorphous silicon film and temperature falls after that. 0005 Then, a polycrystalline silicon film is patterned, silicon oxide is formed on the polycrystalline silicon film after patterning, and the metal membrane of low electric resistance, such as Ta, Cr, and Mo, is further formed on it. And a gate electrode is formed by patterning the metal membrane concerned. 0006 Subsequently, by performing ion doping which uses as a mask the resist used for patterning of a gate electrode or the gate electrode concerned, the impurity of N type or P type is introduced into a polycrystalline silicon film, and a source/drain area is formed in self align. That is, TFT of an n channel type MOS (NMOS) transistor is formed in the portion which introduced the impurity of N type, and TFT of a p channel type MOS (PMOS) transistor is formed in the portion into which the P type impurity was introduced. 0007 Then, silicon oxide is deposited and a contact hole is formed on the source / drain area of TFT, and a gate electrode. And metal membranes (for example, aluminum, W, Mo, etc.) are deposited, and wiring of a source/drain, and a gate is performed by patterning it. A TFT-liquid-crystal display panel (TFT panel) is completed by furthermore forming films, such as an insulator layer, a transparent electrode, a liquid crystal, a polarization film, and a light filter, one by one on this TFT. 0008 Laser annealing by the above-mentioned excimer laser (wavelength of 308 nm) is performed by scanning an amorphous silicon film by a laser beam (scan) (for example, patent documents 1). At this time, a laser beam is linear spot form perpendicular to a scanning direction (scanning direction), and it is common to be fabricated so that that irradiation energy density may become a profile of top flat distribution. Specifically, for example, the laser beam of 0.4 mm in width, and 250 mm in length a line spot It glares as a 300-Hz pulse, piles up toward the cross direction of the line spot, and scans by 95% of scan pitch (feed pitch) (that is, it scans so that the pulse of two continuous laser beams may lap 95% mutually). In the case of 95% of a pile, a scan pitch will be set to 20 micrometers if the width of a linear laser beam is 0.4 mm. 0009 In a excimer laser annealing, the irradiation-energy-density profile of laser. (A profile may only be called hereafter) is top flat distribution, and also light with a wavelength of 308 nm is one with short (about 7 nm) osmosis length that it is easy to be absorbed within amorphous silicon and polycrystalline silicon, and only the surface of a silicone film is heated and it can tend to do the temperature gradient in a thickness direction. Then, the pars basilaris ossis occipitalis is irradiated with laser with the irradiation energy density which is a grade in which a crystal nucleus remains, without the whole silicone film carrying out melting, and growing up a crystal from the crystal nucleus of the pars basilaris ossis occipitalis concerned is performed. If the irradiation energy density of laser is temporarily high, it will become with a supercooling state in the case of cooling if the whole silicone film carries out melting and a crystal nucleus is lost, and it becomes the temperature in which a crystal nucleus is formed automatically, in order to make many crystal nuclei and to solidify at a stretch, it will be an aggregate of micro crystallite. 0010 308-nm light with polycrystalline silicon and melted silicon Since the absorptivity is almost the same, If the irradiation energy beyond a threshold is received as a result of irradiating laser in piles after that even if a once big crystal is formed of laser radiation, it will micro-crystallite-ize according to the above-mentioned mechanism. Therefore, there is a problem that the formation technique of the polycrystalline silicon by a excimer laser annealing has a narrow margin of the irradiation energy density of laser. 0011 Usually, if irradiation energy density of laser is made high, the crystal grain diameter of silicon can be enlarged. However, when the margin of the irradiation energy density of laser is narrow, with dispersion in irradiation energy density, it is easy to reach the irradiation energy beyond the above-mentioned threshold, and micro crystallite-ization of silicon arises as mentioned above. That is, in a excimer laser annealing, it is easy to generate micro crystallite-ization by dispersion in irradiation energy density, and a crystal grain diameter can seldom be enlarged. 0012 The ultraviolet rays which make discharge the discharge gas of XeCl gas and are emitted as excimer laser are used. However, since it is necessary to perform a gas exchange frequently and also and reactivity is high, the discharge gas is short-life and a discharge electrode is also corroded, a periodical discharge chamber also needs to be exchanged. The quartz window which it is easy to produce the affix decomposed by ultraviolet rays in an optical system, and is exposed to the open air needs to be exchanged. Thus, a excimer laser annealer requires a labor great for its maintenance and maintenance, and expense. 0013 In YAG2omega laser, although the energy per pulse is small under the single figure of excimer laser, repeat frequency is higher than excimer laser a single figure. Then, it crystallizes by narrowing down a beam to the half breadth of about 40 micrometers, raising irradiation energy density beyond the threshold in which silicon carries out melting, and making a laser beam scan by a narrow scan pitch of 3 micrometers or less. YAG2omega laser enables it to narrow down a beam to the half breadth of 40 micrometers that beam quality is good. 0014 On the other hand, in the laser annealing by YAG2omega laser, the wavelength of YAG2omega laser is 532 nm, and the osmosis length of polycrystalline silicon is excellent in perviousness for a long time with 830 nm. Therefore, there is little attenuation within a silicone film, and since a silicone film is heated uniformly, it is hard to produce the temperature gradient of the thickness direction. For this reason, the whole film tends to carry out melting also of the depth direction thoroughly. Therefore, in the boundary part of the fusion part in which silicon carried out melting thoroughly by laser radiation, and the non-fusion part which is not so, there is the feature in which a crystal grows up to be a transverse direction easily toward the inside of a fusion part from a non-fusion part in the case of cooling after laser radiation. 0015 Since the absorptivity in polycrystalline silicon is low as compared with melted silicon, YAG2omega laser with a wavelength of 532 nm differs in the rate of an endothermic the grain boundary part which melting starts early by laser radiation, and inside which are started late a crystal. Therefore, even if it is hard to remelt even if laser is irradiated in piles by the once crystallized polycrystalline silicon, and irradiation energy density varies somewhat, itis micro-crystallite- hard toize the once formed big crystal in YAG2omega laser annealing after that. Therefore, the formation technique of the polycrystalline silicon by YAG2omega laser annealing has the advantage that the margin of the irradiation energy density of laser is larger than the case of a excimer laser annealing. 0016 the expandable part in YAG2omega laser annealing equipment Nd3+ with a wavelength of 1064 nm: It is only a wavelength changing crystal for changing an YAG laser into YAG2omega laser with a wavelength of 532 nm, and since generating of the affix to an optic does not take place easily, either, its maintenance and maintenance are far easy as compared with a excimer laser annealer. 0017 By the way, generally, if excimer laser or an YAG laser is irradiated with a silicone film, the surface roughness will increase it. This is for a projection to occur in a grain boundary part, and the projection becomes so large that a crystal grain diameter is large. As a cause that a projection is possible, it is possible that the density of melted silicon is larger than the density of solid silicon. Namely, since volume increases silicon when volume decreases when carrying out melting by laser radiation, and solidifying after that (crystallization), If the silicon which carried out melting crystallizes a crystal nucleus, growing up as a starting point, the melted silicon extruded by originating in the increase in volume by the grain boundary part solidified at the end can gather up, and it will form a projection. 0018 The increase in the surface roughness of the silicone film by this projection becomes a cause which causes the fall of the reliability of TFT formed in it. Although TFT serves as the structure of having the gate electrode formed via the insulator layer on the silicone film, if a projection is on the surface of a silicone film, when voltag