JP4526764B2 - Semiconductor device and semiconductor device production system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device configured using a semiconductor film having a crystal structure, and more particularly to a semiconductor device using a thin film transistor having a crystalline semiconductor film grown on an insulating surface as an active layer. Further, the present invention relates to a semiconductor device production system using laser light.
[0002]
[Prior art]
In recent years, a technology for forming a TFT on a substrate has greatly advanced, and application development to an active matrix semiconductor display device has been advanced. In particular, a TFT using a polycrystalline semiconductor film (polysilicon TFT) has higher field effect mobility (also referred to as mobility) than a TFT using a conventional amorphous semiconductor film, and thus can operate at high speed. For this reason, it is possible to perform control of a pixel, which has been conventionally performed by a drive circuit provided outside the substrate, with a drive circuit formed on the same substrate as the pixel.
[0003]
By the way, as a substrate used for a semiconductor device, a glass substrate is considered promising rather than a single crystal silicon substrate in terms of cost. A glass substrate is inferior in heat resistance and easily deforms by heat. Therefore, in the case where a polysilicon TFT is formed on a glass substrate, using laser annealing for crystallization of the semiconductor film is very effective for avoiding thermal deformation of the glass substrate.
[0004]
The characteristics of laser annealing are that the processing time can be greatly shortened compared to annealing methods using radiation heating or conduction heating, and the substrate or semiconductor film is selectively and locally heated to cause almost thermal damage to the substrate. Is not given.
[0005]
The laser annealing method here refers to a technique for recrystallizing a damaged layer formed on a semiconductor substrate or a semiconductor film, or a technique for crystallizing a semiconductor film formed on a substrate. Moreover, the technique applied to planarization and surface modification of a semiconductor substrate or a semiconductor film is also included. The laser oscillation device to be applied is a gas laser oscillation device typified by an excimer laser, or a solid-state laser oscillation device typified by a YAG laser, and a semiconductor surface layer is irradiated with laser light for several tens of nano to several tens of microseconds. It is known to be crystallized by heating for a very short time.
[0006]
Lasers are roughly classified into two types, pulse oscillation and continuous oscillation, depending on the oscillation method. Pulsed lasers have a relatively high output energy, so the size of the laser beam is several centimeters. ² As described above, mass productivity can be improved. In particular, when the shape of a laser beam is processed using an optical system to form a linear shape having a length of 10 cm or more, the substrate can be efficiently irradiated with laser light, and mass productivity can be further improved. For this reason, it has become the mainstream to use a pulsed laser for crystallization of the semiconductor film.
[0007]
However, in recent years, it has been found that the crystal grain size formed in a semiconductor film is larger when a continuous wave laser is used than when a pulsed laser is used for crystallization of a semiconductor film. As the crystal grain size in the semiconductor film increases, the mobility of TFTs formed using the semiconductor film increases. For this reason, continuous wave lasers are starting to attract attention.
[0008]
Note that attempts to form a single crystal semiconductor film on an insulating surface have been made for a long time, and a technique called graphoepitaxy has been devised as a more aggressive attempt. Graphoepitaxy forms a step on the surface of a quartz substrate, forms an amorphous semiconductor film or a polycrystalline semiconductor film on it, and then heats it with a laser beam or heater to form the step shape formed on the quartz substrate. This is a technique of forming an epitaxial growth layer with nuclei as a nucleus. This technique is disclosed in Non-Patent Document 1, for example.
[0009]
[Non-Patent Document 1]
J. Vac. Sci. Technol., "Grapho-epitaxy of silicon on fused silica using surface micropatterns and laser crystallization", 16 (6), 1979, pp1640-1643.
[0010]
Further, for example, Non-Patent Document 2 also discloses a semiconductor film crystallization technique called graphoepitaxy. This was an attempt to epitaxially grow a semiconductor film by induction of a surface relief grating on the surface of an artificially produced amorphous substrate. In Non-Patent Document 2, the technique of graphoepitaxy is to provide a step on the surface of the insulating film and to perform a treatment such as heating or laser light irradiation on the semiconductor film formed on the insulating film, It is disclosed that the crystal of the semiconductor film is epitaxially grown.
[0011]
[Non-Patent Document 2]
MW Geis, et al., "CRYSTALLINE SILICON ON INSULATORS BY GRAPHOEPITAXY" Technical Digest of International Electron Devices Meeting, 1979, pp.210.
[0012]
[Problems to be solved by the invention]
A crystalline semiconductor film manufactured using a laser annealing method roughly divided into pulse oscillation and continuous oscillation is generally formed by aggregating a plurality of crystal grains. The position and size of the crystal grains are random, and it is difficult to form a crystalline semiconductor film by specifying the position and size of the crystal grains. Therefore, an interface (grain boundary) of crystal grains may exist in the active layer formed by patterning the crystalline semiconductor film into an island shape.
[0013]
Unlike crystal grains, there are innumerable recombination centers and trap centers due to amorphous structures and crystal defects at grain boundaries. It is known that when carriers are trapped in this trapping center, the grain boundary potential increases and becomes a barrier against the carriers, so that the current transport characteristics of the carriers decrease. Therefore, if there is a grain boundary in the active layer of the TFT, particularly in the channel formation region, the mobility of the TFT is significantly reduced, the on-current is reduced, and the current flows at the grain boundary, so that the off-current increases. However, it has a significant effect on the TFT characteristics. In addition, in a plurality of TFTs manufactured on the assumption that the same characteristics can be obtained, the characteristics vary depending on the presence or absence of grain boundaries in the active layer.
[0014]
The reason why the position and size of the obtained crystal grains are random when the semiconductor film is irradiated with laser light is as follows. It takes a certain amount of time for solid-phase nucleation to occur in a liquid semiconductor film completely melted by laser light irradiation. As time passes, innumerable crystal nuclei are generated in the complete melting region, and crystals grow from the crystal nuclei. Since the positions where the crystal nuclei are generated are random, the crystal nuclei are unevenly distributed. Then, since crystal growth ends when the crystal grains collide with each other, the position and size of the crystal grains are random.
[0015]
Therefore, it is ideal to form the channel formation region having a significant influence on the characteristics of the TFT with a single crystal grain by eliminating the influence of the grain boundary, but a crystalline silicon film having no grain boundary is formed. It was almost impossible to form by laser annealing. Therefore, a TFT having an active layer made of a crystalline silicon film crystallized using a laser annealing method has not been obtained until now, which is equivalent to the characteristics of a MOS transistor manufactured on a single crystal silicon substrate.
[0016]
In view of the above-described problems, the present invention prevents the formation of grain boundaries in the channel formation region of the TFT, and the grain boundary significantly reduces the mobility of the TFT, reduces the on-current, and increases the off-current. It is an object of the present invention to provide a semiconductor device production system using a laser crystallization method that can prevent the occurrence of the problem.
[0017]
[Means for Solving the Problems]
The inventors of the present invention formed a semiconductor film on an uneven insulating film and irradiated the laser beam with the semiconductor film, thereby generating crystal nuclei in the vicinity of the concave bottom portion of the concave portion of the insulating film or the convex top portion of the convex portion. The inventors have found that crystal growth proceeds from the crystal nucleus toward a direction parallel to the insulating film. In addition, a recessed part points out the recessed area | region in which the convex part is not formed.
[0018]
This mechanism will be described with reference to FIG. FIG. 1A shows a state where the semiconductor film 11 is formed over the insulating film 10 having the convex portions 10a. After the semiconductor film 11 is melted by the laser light irradiation, the heat in the semiconductor film 11 is radiated to the insulating film 10. At this time, heat is efficiently radiated in a portion having a larger area in contact with the insulating film. For example, in FIG. 1A, the portions 14 and 15 where the contacting surfaces intersect each other are the insulating films rather than the portions 12 and 13 where the surfaces where the semiconductor film 11 and the insulating film 10 are in contact are flat. The heat dissipation is efficient, and crystal nuclei are formed faster. In addition, heat is radiated more efficiently in the portion where the heat capacity of the insulating film is larger. For example, since the heat capacity is larger in the vicinity of the edge 14 of the concave portion than in the vicinity of the edge 15 of the convex portion because the volume of the insulating film in a certain range is larger, the escaped heat is less likely to be trapped and heat is efficiently dissipated. . Therefore, near the edge 14 of the concave portion, the crystal nucleus can be formed faster than near the edge 15 of the convex portion.
[0019]
As time elapses, crystal growth proceeds from the crystal nucleus generated in the vicinity 14 of the recess edge toward the direction parallel to the insulating film. With reference to FIG. 1B, the crystal growth direction of the semiconductor film will be described. FIG. 1B shows a state where the semiconductor film 11 is formed over the insulating film 10 having the two convex portions 10a and 10b. In the semiconductor film 11, crystal growth proceeds in the direction indicated by the arrow from near the edge 14 of the recess. Then, the crystal growth proceeding from the vicinity of the edge 14 of the adjacent recess collides with each other in the vicinity of the middle, and forms a grain boundary 16 to stop the crystal growth.
[0020]
As described above, when the insulating film provided with the convex portion is crystallized by irradiation with laser light, the position where the grain boundary is formed can be controlled to some extent. Therefore, at the stage where the shape of the insulating film is designed, the position where the grain boundary of the semiconductor film is formed can be predicted to some extent. That is, according to the present invention, the position where the grain boundary is formed can be selectively determined, so that it is possible to lay out the active layer so that the grain boundary is not included in the active layer, more preferably the channel formation region. Become.
[0021]
Specifically, the insulating film is provided with stripes (stripes) or rectangular unevenness. Then, the semiconductor film formed on the insulating film is irradiated with continuous oscillation laser light along the unevenness of the stripes of the insulating film, or along the major axis or minor axis direction of the rectangle. At this time, it is most preferable to use a continuous wave laser beam, but a pulsed laser beam may be used. Note that the cross section of the convex portion in the direction perpendicular to the scanning direction of the laser beam may be a rectangle, a triangle, or a trapezoid.
[0022]
In the vicinity of the center between the edges of the adjacent protrusions of the semiconductor film and the vicinity of the center between the edges of the recesses, there are grain boundaries formed by the crystals that have grown. Therefore, in the present invention, the portion 17 between the vicinity of the edge of the recess and the vicinity of the center between the edges of the recess is relatively free from the formation of a grain boundary and has excellent crystallinity as the active layer or channel formation region. Alternatively, a portion 18 between the vicinity of the edge of the convex portion and the vicinity of the center between the edges of the convex portion, in which the grain boundary is relatively hardly formed and has excellent crystallinity, is used as the active layer or the channel formation region. The portions 17 and 18 having excellent crystallinity do not necessarily include a grain boundary, but the crystallinity is relatively excellent because the crystal grain is large even if a grain boundary exists.
[0023]
In the present invention, it is possible to prevent the formation of grain boundaries in the channel formation region of the TFT by actively using the portions 17 and 18 having excellent crystallinity as the active layer of the TFT. It is possible to prevent the mobility of the TFT from being significantly lowered, the on-current is reduced, and the off-current is increased. It should be noted that the designer can appropriately determine how far is removed by patterning in the vicinity of the edge of the convex portion or the concave portion.
[0024]
Note that the energy density in the vicinity of the edge of the laser beam of the laser light is generally lower than that in the vicinity of the center, and the crystallinity of the semiconductor film is often poor. For this reason, when scanning with laser light, it is desirable that the portion that will later become the channel formation region of the TFT and the edge of the locus do not overlap.
[0025]
Therefore, in the production system of the present invention, the data (pattern information) of the shape of the insulating film or the semiconductor film viewed from the upper surface of the substrate obtained at the design stage is first stored in the storage means. Then, from the pattern information and the width of the laser beam in the direction perpendicular to the scanning direction of the laser beam, at least the portion that becomes the channel formation region of the TFT and the edge of the laser beam trajectory do not overlap. Determine the scan path. Then, the position of the substrate is aligned with the marker as a reference, and the semiconductor film on the substrate is irradiated with laser light according to the determined scanning path.
[0026]
With the above-described configuration, it is possible to scan the laser beam only at least indispensable portions, instead of irradiating the entire substrate with the laser beam. Accordingly, it is possible to save time for irradiating the unnecessary portion with the laser beam, thereby shortening the time required for the laser beam irradiation and improving the processing speed of the substrate. Further, unnecessary portions can be irradiated with laser light to prevent the substrate from being damaged.
[0027]
Note that the marker may be formed by directly etching the substrate with a laser beam or the like, or the marker may be formed on a part of the insulating film at the same time when the insulating film having unevenness is formed. . In addition, the shape of the actually formed insulating film or semiconductor film is read using an imaging device such as a CCD, stored as data in the first storage means, and the insulation obtained at the design stage in the second storage means. The pattern information of the film or semiconductor film is stored, and the substrate is aligned by collating the data stored in the first storage unit with the pattern information stored in the second storage unit Anyway.
[0028]
By forming a marker on a part of the insulating film or using the shape of the insulating film as a marker, the marker mask can be reduced by one, and more accurate than forming with a laser beam on the substrate. A marker can be formed at a position, and the alignment accuracy can be improved.
[0029]
In general, the energy density of laser light is not completely uniform, and the height varies depending on the position in the laser beam. In the present invention, it is necessary to irradiate a laser beam having a constant energy density to a portion which becomes a channel forming region at least, more preferably, the entire flat surface of the concave portion or the entire flat surface of the convex portion. Therefore, in the present invention, by scanning with laser light, a region having a uniform energy density is completely overlapped with at least a portion that becomes a channel formation region, more preferably, the entire flat surface of the concave portion or the entire flat surface of the convex portion. It is necessary to use a laser beam having an energy density distribution. In order to satisfy the above energy density condition, it is desirable that the shape of the laser beam be rectangular or linear.
[0030]
Further, a portion of the laser beam having a low energy density may be shielded through a slit. By using the slit, a laser beam having a relatively uniform energy density can be applied to the entire flat surface of the concave portion or the entire flat surface of the convex portion, and crystallization can be performed uniformly. Further, by providing the slit, the width of the laser beam can be partially changed depending on the pattern information of the insulating film or the semiconductor film, and the restrictions on the layout of the channel formation region and the active layer of the TFT can be reduced. The width of the laser beam means the length of the laser beam in the direction perpendicular to the scanning direction.
[0031]
A single laser beam obtained by synthesizing laser beams oscillated from a plurality of laser oscillation devices may be used for laser crystallization. With the above configuration, it is possible to compensate for the weak energy density of each laser beam.
[0032]
In the insulating film having unevenness, in the direction perpendicular to the scanning direction of the laser beam, the restriction on the layout of the semiconductor film used as the active layer of the TFT becomes smaller when the width of the concave bottom portion is wider than the width of the convex top portion. So desirable. Specifically, in the direction perpendicular to the longitudinal direction of the unevenness of the insulating film, it is desirable that the width of the concave bottom portion is three times or more the width of the convex top portion.
[0033]
In addition, after the semiconductor film is formed, laser light irradiation is performed so that the semiconductor film is not crystallized so that the semiconductor film is not exposed to the air (for example, a specified gas atmosphere such as a rare gas, nitrogen, oxygen, or a reduced pressure atmosphere). Also good. With the above configuration, contaminants at the molecular level in the clean room, such as boron contained in a filter for increasing the cleanliness of air, can be prevented from being mixed into the semiconductor film during crystallization by laser light. it can.
[0034]
The conventional semiconductor film crystallization technology called graphoepitaxy is an attempt to epitaxially grow a semiconductor film by inducing a surface relief grating on the surface of an artificially produced amorphous substrate. Met. The technology related to the graphoepitaxy is described in Non-Patent Document 2 and the like. In the above papers and the like, the graphoepitaxy technique is a technique in which a step is provided on the surface of an insulating film, and the semiconductor film formed on the insulating film is subjected to a treatment such as heating or laser light irradiation. Epitaxial growth of film crystals is disclosed. However, the temperature required for the epitaxial growth is required to be at least about 700 ° C. When the epitaxial growth is performed on the glass substrate, a grain boundary is formed in the semiconductor film in the vicinity of the edge of the concave portion or the convex portion of the insulating film. In the present invention, the shape of the concave portion or convex portion of the insulating film and the position of the edge are designed in accordance with the layout of the island so that the island mask is laid out and the crystallinity in the portion to be the island can be improved. Specifically, the shape, size, and the like of the concave portion or the convex portion are determined so that the edge of the concave portion or the convex portion and the center between the edges of the concave portion or the convex portion do not overlap with the island. Then, using the insulating film designed in accordance with the island layout, the position of the grain boundary is selectively determined intentionally. Then, a part where the selectively formed grain boundary exists in the semiconductor film is removed by patterning, and a part with relatively excellent crystallinity is used as an island. Therefore, the technique disclosed in the present invention is the same as conventional graphoepitaxy in that a semiconductor film is formed on an insulating film provided with a step, and the semiconductor film is crystallized using the step. This grapho epitaxy does not include the concept of controlling the position of grain boundaries using steps and reducing the grain boundaries in the island, and is similar to the present invention.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
Next, the laser light irradiation method used in the present invention will be described with reference to FIG.
[0036]
First, the insulating film 101 is formed over the substrate 100 as illustrated in FIG. The insulating film 101 includes striped convex portions 101a. The method for forming the unevenness will be described in detail later. As the insulating film 101, a silicon oxide film, a silicon oxynitride film, a silicon nitride film, or the like can be used. Note that an impurity such as an alkali metal can be prevented from being taken into a semiconductor film to be formed later, an insulating film that can withstand a subsequent processing temperature, and unevenness can be formed. These other insulating films may be used. Alternatively, a stacked structure of two or more films may be used.
[0037]
At this time, the marker may be formed using a part of the insulating film simultaneously with the insulating film 101.
[0038]
The substrate 100 may be made of any material that can withstand the processing temperature of the subsequent process. For example, a quartz substrate, a silicon substrate, a glass substrate such as barium borosilicate glass or alumino borosilicate glass, a metal substrate, or a stainless steel substrate is provided with an insulating film. A substrate on which is formed can be used. Further, a plastic substrate having heat resistance enough to withstand the processing temperature may be used.
[0039]
Next, the semiconductor film 102 is formed so as to cover the insulating film 101. The semiconductor film 102 can be formed by a known means (a sputtering method, an LPCVD method, a plasma CVD method, or the like). Note that the semiconductor film may be an amorphous semiconductor film, a microcrystalline semiconductor film, or a crystalline semiconductor film. In addition to silicon, silicon germanium may be used.
[0040]
At this time, unevenness appears in the semiconductor film 102 along the unevenness of the insulating film 101. Note that the size of the convex portion 101a of the insulating film 101 can be set as appropriate by the designer, but it is necessary to set the thickness so that a semiconductor film to be formed later does not cause film breakage in the vicinity of the edge of the convex portion. There is. In the case where the active layer is laid out in the concave portion, the width of the concave portion is made wider than the width of the convex portion, so that the restriction on the layout of the active layer can be reduced. When the active layer is laid out in the convex portion, the width of the convex portion is made wider than the width of the concave portion, thereby making it possible to reduce the restrictions on the layout of the active layer. In the present embodiment, in the direction perpendicular to the scanning direction of the laser beam, for example, the width of the flat portion of the concave portion is set to be twice or more the width of the flat portion of the convex portion, and the width of the convex portion is 300 to It was 3000 nm. Furthermore, the height of the convex portion was set to 30 to 300 nm.
[0041]
Next, as shown in FIG. 2A, the semiconductor film 102 is irradiated with laser light to form a semiconductor film 103 (after LC) with improved crystallinity. The energy density of the laser beam is low in the vicinity of the edge of the laser beam 104. Therefore, the crystal grain is small in the vicinity of the edge, and a protruding portion (ridge) appears along the crystal grain boundary. Therefore, the edge of the locus of the laser beam 104 of the laser beam and the portion that becomes the channel formation region are not overlapped.
[0042]
The scanning direction of the laser light is determined so as to be parallel to the direction of the convex portion 101a as indicated by an arrow.
[0043]
In the present invention, a known laser can be used. Although it is desirable that the laser light is continuous oscillation, it is considered that the effect of the present invention can be obtained to some extent even if it is pulse oscillation. As the laser, a gas laser or a solid laser can be used. There are excimer laser, Ar laser, Kr laser, etc. as gas laser, and YAG laser, YVO as solid laser. _Four Laser, YLF laser, YAlO _Three Laser, glass laser, ruby laser, alexandride laser, Ti: sapphire laser, Y ₂ O _Three A laser etc. are mentioned. Solid lasers include YAG, YVO doped with Cr, Nd, Er, Ho, Ce, Co, Ti, Yb or Tm. _Four , YLF, YAlO _Three Lasers using crystals such as are applied. The fundamental wave of the laser differs depending on the material to be doped, and a laser beam having a fundamental wave of about 1 μm can be obtained. The harmonic with respect to the fundamental wave can be obtained by using a nonlinear optical element.
[0044]
Furthermore, after converting infrared laser light emitted from a solid-state laser into green laser light by a nonlinear optical element, ultraviolet laser light obtained by another nonlinear optical element can also be used.
[0045]
Note that the cross-sectional view taken along the line AA ′ in FIG. 2A before crystallization corresponds to FIG. 2B, and the cross-sectional view taken along the line BB ′ after crystallization is shown in FIG. ). In the semiconductor film 103 (after LC) crystallized by laser light irradiation, a grain boundary 105 is likely to occur in the vicinity of the center of the recess of the insulating film 101. In FIG. 2, a portion 106 between the vicinity of the edge of the recess and the vicinity of the center between the edges of the recess is relatively free from the formation of a grain boundary and has excellent crystallinity as the active layer or channel formation region. The portion 106 having excellent crystallinity does not necessarily include a grain boundary, but the crystallinity is relatively excellent because the crystal grain is large even if there is a grain boundary. In addition, a portion between the vicinity of the convex portion edge and the central portion between the convex portion edges that is relatively hard to form a grain boundary and excellent in crystallinity is used as an active layer or a channel formation region. Also good.
[0046]
Next, as shown in FIG. 3A, do not use the vicinity of the center between the edges of the recesses, which are considered to have many grain boundaries, and the semiconductor film in the vicinity of the projections as channel formation regions. Then, the crystallized semiconductor film 103 is patterned, and an island-shaped semiconductor film (island) 108 is formed using a portion having excellent crystallinity between the vicinity of the edge of the recess and the vicinity of the center between the edges of the recess. Form.
[0047]
In this embodiment, the semiconductor film 103 is patterned so as to leave a portion near the edge of the convex portion or near the edge of the concave portion, and the vicinity of the convex portion and the vicinity of the center of the concave portion, as shown in FIG. In this manner, the island 108 used as a slit-like active layer separated only in the channel formation region was formed. A cross-sectional view taken along the line AA ′ of the island 108 is shown in FIG. 3B, and a cross-sectional view taken along the line BB ′ is shown in FIG. The portion that becomes the source region or the drain region is less affected by the crystallinity of the semiconductor film on the TFT characteristics than the channel formation region. Therefore, even if a portion of the semiconductor film having poor crystallinity is used as the source region or the drain region, it does not matter so much.
[0048]
Next, as illustrated in FIG. 4A, a gate insulating film 110 is formed so as to cover at least a portion to be a channel formation region of the island 108. Note that in FIG. 4A, the source region or the drain region is exposed, but the entire island 108 may be covered with the gate insulating film 110.
[0049]
Next, a gate electrode 111 is formed by forming and patterning a conductive film. Note that FIG. 4B is a cross-sectional view taken along line AA ′ in FIG. The gate electrode 111 overlaps with all channel formation regions.
[0050]
Through the above manufacturing process, a TFT having a plurality of channel formation regions separated from each other is completed. With such a structure, it is possible to efficiently dissipate heat generated by driving the TFT while ensuring on-current by increasing the channel width of the channel formation region.
[0051]
Next, the production system of the present invention will be described. FIG. 5 shows a flowchart of the production system of the present invention. First, an island mask is designed, and then the shape of the insulating film is designed to have striped or rectangular irregularities. At this time, one or more of the islands are laid out on the flat surface of the concave or convex portion of the insulating film. Furthermore, it is desirable that the island be laid out so as to avoid a portion near the center between the edges of the concave or convex portions where the grain boundary is relatively easily formed. When the island is used as the active layer of the TFT, it is desirable to align the carrier direction of the channel formation region with the direction of the stripe of the insulating film or the long side or the short side of the rectangle. Accordingly, the directions may be intentionally not aligned.
[0052]
At this time, the shape of the insulating film may be designed so that a marker is formed on a part of the insulating film.
[0053]
And the information (pattern information) regarding the shape of the designed insulating film is input into the computer which a laser irradiation apparatus has, and is memorize | stored in the memory | storage means. In the computer, the scanning path of the laser beam is determined based on the inputted pattern information of the insulating film and the width in the direction perpendicular to the scanning direction of the laser beam. At this time, it is important to determine the scanning path so that the edge of the locus of the laser beam does not overlap the flat surface of the concave or convex portion of the insulating film. In addition to the insulating film pattern information, the island pattern information is stored in the storage means of the computer so that the scanning path is determined so that the edge of the laser beam trajectory does not overlap the island or the channel formation region of the island. Anyway.
[0054]
Note that when the width of the laser beam is controlled by providing a slit, the computer grasps the width of the concave portion or the convex portion of the insulating film in the direction perpendicular to the scanning direction based on the input insulating film pattern information. In consideration of the width of the concave or convex portion of the insulating film, the edge of the laser beam trajectory and the flat surface of the concave or convex portion of the insulating film do not overlap with each other in the direction perpendicular to the scanning direction. Set the slit width.
[0055]
On the other hand, an insulating film is formed on the substrate in accordance with the designed pattern information, and then a semiconductor film is formed on the insulating film. And after forming a semiconductor film, a board | substrate is installed in the stage of a laser irradiation apparatus, and alignment of a board | substrate is performed. FIG. 5 shows an example in which a marker is detected using a CCD camera and the substrate is aligned. The CCD camera means a camera using a CCD (charge coupled device) as an image sensor.
[0056]
In addition, the pattern information of the insulating film or semiconductor film on the substrate placed on the stage is detected by a CCD camera or the like, and the pattern information of the insulating film or semiconductor film designed by CAD in the computer and obtained by the CCD camera are actually The substrate may be aligned by comparing the pattern information of the insulating film or semiconductor film formed on the substrate.
[0057]
Then, the semiconductor film is crystallized by irradiating laser light according to a predetermined scanning path.
[0058]
Next, after irradiation with laser light, the semiconductor film whose crystallinity is enhanced by laser light irradiation is patterned to form islands. Thereafter, a process of manufacturing a TFT from the island is performed. A specific manufacturing process of the TFT differs depending on the shape of the TFT, but typically, a gate insulating film is formed and an impurity region is formed in the island. Then, an interlayer insulating film is formed so as to cover the gate insulating film and the gate electrode, a contact hole is formed in the interlayer insulating film, and a part of the impurity region is exposed. Then, a wiring is formed on the interlayer insulating film so as to be in contact with the impurity region through the contact hole.
[0059]
Next, the structure of the laser irradiation apparatus used in the present invention will be described with reference to FIG. Reference numeral 151 denotes a laser oscillation device. Although four laser oscillation devices are used in FIG. 6, the number of laser oscillation devices included in the laser irradiation device is not limited to this number.
[0060]
Note that the laser oscillation device 151 may use a chiller 152 to keep the temperature constant. The chiller 152 is not necessarily provided, but by keeping the temperature of the laser oscillation device 151 constant, it is possible to suppress the energy of the output laser light from varying depending on the temperature.
[0061]
Reference numeral 154 denotes an optical system which can focus the laser beam by changing the optical path output from the laser oscillation device 151 or processing the shape of the laser beam. Further, in the laser irradiation apparatus of FIG. 6, the laser beams of the laser beams output from the plurality of laser oscillation apparatuses 151 can be combined by the optical system 154 by overlapping each other.
[0062]
Note that an AO modulator 153 that changes the traveling direction of the laser light in an extremely short time may be provided in the optical path between the substrate 156 that is an object to be processed and the laser oscillation device 151. Further, instead of the AO modulator, an attenuator (light quantity adjustment filter) may be provided to adjust the energy density of the laser light.
[0063]
Further, a means (energy density measuring means) 165 for measuring the energy density of the laser beam output from the laser oscillation device 151 is provided in the optical path between the substrate 156 that is the object to be processed and the laser oscillation device 151, and the measurement is performed. The computer 160 may monitor the change in energy density over time. In this case, the output from the laser oscillation device 160 may be increased so as to compensate for the attenuation of the energy density of the laser beam.
[0064]
The combined laser beam is applied to the substrate 156 that is an object to be processed through the slit 155. The slit 155 is preferably formed of a material that can block the laser beam and that is not deformed or damaged by the laser beam. The slit 155 has a variable width, and the width of the laser beam can be changed according to the width of the slit.
[0065]
Note that the shape of the laser beam on the substrate 156 of the laser light oscillated from the laser oscillation device 151 when not passing through the slit 155 differs depending on the type of laser, and can also be formed by an optical system.
[0066]
The substrate 156 is placed on the stage 157. In FIG. 6, the position control means 158 and 159 correspond to means for controlling the position of the laser beam on the workpiece, and the position of the stage 157 is controlled by the position control means 158 and 159.
[0067]
In FIG. 6, the position control means 158 controls the position of the stage 157 in the X direction, and the position control means 159 controls the position of the stage 157 in the Y direction.
[0068]
Further, the laser irradiation apparatus of FIG. 6 has a computer 160 having both storage means such as a memory and a central processing unit. The computer 160 controls the position control means 158 and 159 so as to control the oscillation of the laser oscillating device 151, determine the scanning path of the laser light, and scan the laser beam of the laser light according to the determined scanning path. The substrate can be moved to a predetermined position.
[0069]
In FIG. 6, the position of the laser beam is controlled by moving the substrate, but it may be moved using an optical system such as a galvanometer mirror, or both.
[0070]
Further, in FIG. 6, the width of the slit 155 can be controlled by the computer 160 and the width of the laser beam can be changed according to the mask pattern information. Note that the slit is not necessarily provided.
[0071]
Further, the laser irradiation apparatus may include a means for adjusting the temperature of the object to be processed. Further, since the laser light is light having high directivity and energy density, a damper may be provided to prevent the reflected light from being irradiated to an inappropriate place. The damper desirably has a property of absorbing reflected light, and cooling water may be circulated in the damper to prevent the temperature of the partition wall from rising due to absorption of the reflected light. Further, the stage 157 may be provided with means for heating the substrate (substrate heating means).
[0072]
When the marker is formed by a laser, a marker laser oscillation device may be provided. In this case, the oscillation of the marker laser oscillation device may be controlled by the computer 160. Further, in the case where a marker laser oscillation device is provided, an optical system for condensing the laser beam output from the marker laser oscillation device is separately provided. The laser used for forming the marker is typically a YAG laser or CO. ₂ A laser or the like can be mentioned, but it is of course possible to form using other lasers.
[0073]
Further, one CCD camera 163 may be provided for positioning using a marker, and in some cases, several CCD cameras 163 may be provided. The CCD camera means a camera using a CCD (charge coupled device) as an image sensor.
[0074]
Note that the substrate may be aligned by recognizing the pattern of the insulating film or the semiconductor film by the CCD camera 163 without providing the marker. In this case, the pattern information of the insulating film or semiconductor film by the mask input to the computer 160 is compared with the actual insulating film or semiconductor film pattern information collected by the CCD camera 163 to grasp the position information of the substrate. can do. In this case, it is not necessary to provide a marker separately.
[0075]
In addition, the laser light incident on the substrate is reflected by the surface of the substrate and returns to the same optical path as the incident light, which is so-called return light, but the return light is a change in laser output and frequency, rod breakage, etc. Adverse effects. Therefore, an isolator may be installed in order to remove the return light and stabilize the oscillation of the laser.
[0076]
Although FIG. 6 shows the configuration of the laser irradiation apparatus provided with a plurality of laser oscillation apparatuses, the number of laser oscillation apparatuses may be one. FIG. 7 shows a configuration of a laser irradiation apparatus having one laser oscillation apparatus. In FIG. 7, 201 is a laser oscillation device, and 202 is a chiller. Reference numeral 215 denotes an energy density measuring device, 203 denotes an AO modulator, 204 denotes an optical system, 205 denotes a slit, and 213 denotes a CCD camera. The substrate 206 is placed on the stage 207, and the position of the stage 207 is controlled by the X direction position control means 208 and the Y direction position control means 209. As in the case shown in FIG. 6, the operation of each means of the laser irradiation apparatus is controlled by the computer 210. The difference from FIG. 6 is that there is one laser oscillation apparatus. Further, unlike the case of FIG. 6, the optical system 204 only needs to have a function of condensing one laser beam.
[0077]
Thus, in the present invention, after crystallization by laser light, the vicinity of the center between the edges of the recesses or protrusions of the semiconductor film is removed by patterning, and the vicinity of the edges of the recesses or protrusions and the edges of the recesses or protrusions Grain boundaries are formed in the channel formation region of the TFT by positively using a portion having relatively high crystallinity, which is relatively difficult to form a grain boundary between the center and the center, as the TFT active layer. It is possible to prevent the TFT mobility from being significantly lowered, the on-current is reduced, and the off-current is increased due to the grain boundaries. It should be noted that the designer can appropriately determine the extent to be removed by patterning as the vicinity of the edge of the concave portion or convex portion.
[0078]
Also, instead of scanning and irradiating the entire semiconductor film with laser light, the semiconductor film is crystallized and removed by patterning by scanning the laser light so that at least the indispensable part can be crystallized at least. The time for irradiating the portion to be irradiated with laser light can be saved, and the processing time per substrate can be greatly shortened.
[0079]
【Example】
Examples of the present invention will be described below.
[0080]
Example 1
In this embodiment, a method for forming an insulating film having unevenness will be described.
[0081]
First, as shown in FIG. 8A, a first insulating film 251 is formed over a substrate 250. In this embodiment, silicon oxynitride is used for the first insulating film 251; however, the first insulating film 251 is not limited thereto, and may be an insulating film having a high selectivity in etching with respect to the second insulating film. In this embodiment, the first insulating film 251 is formed by using a CVD apparatus with SiH. _Four And N ₂ O was used to form a thickness of 50 to 200 nm. Note that the first insulating film may be a single layer or a structure in which a plurality of insulating films are stacked.
[0082]
Next, as illustrated in FIG. 8B, a second insulating film 252 is formed so as to be in contact with the first insulating film 251. When the second insulating film 252 is patterned in a later step to form unevenness, the second insulating film 252 needs to have such a thickness that the unevenness appears on the surface of the semiconductor film to be formed thereafter. In this embodiment, 30 nm to 300 nm of silicon oxide is formed as the second insulating film 252 by a plasma CVD method.
[0083]
Next, as shown in FIG. 8C, a mask 253 is formed, and the second insulating film 252 is etched. In this embodiment, ammonium hydrogen fluoride (NH _Four HF ₂ ) 7.13% and ammonium fluoride (NH _Four Wet etching is performed at 20 ° C. using a mixed solution (product name: LAL500, manufactured by Stella Chemifa Co.) containing 15.4% of F) as an etchant. By this etching, a rectangular or striped convex portion 254 is formed. In this specification, the first insulating film 251 and the convex portion 253 are regarded as one insulating film.
[0084]
Next, a semiconductor film is formed so as to cover the first insulating film 251 and the convex portion 253. In this embodiment, since the thickness of the convex portion is 30 nm to 300 nm, the thickness of the semiconductor film is desirably 50 to 200 nm, and here, 60 nm. Note that if an impurity is mixed between the semiconductor film and the insulating film, the crystallinity of the semiconductor film may be adversely affected, which may increase variations in characteristics of TFTs to be manufactured and variations in threshold voltage. The semiconductor film is preferably formed continuously. Therefore, in this embodiment, after the formation of the insulating film composed of the first insulating film 251 and the convex portion 253, the silicon oxide film 255 is thinly formed on the insulating film and then continuously exposed not to the atmosphere. Then, a semiconductor film 256 is formed. The thickness of the silicon oxide film can be set as appropriate by the designer, but in this embodiment, the thickness is about 5 nm to 30 nm.
[0085]
Note that when the second insulating film 252 is etched, the convex portion may be etched into a tapered shape. By forming the convex portion into a tapered shape, the semiconductor film, the gate insulating film, the gate electrode, and the like formed over the insulating film can be prevented from being cut at the edge of the convex portion.
[0086]
Next, a method for forming an insulating film different from that in FIG. 8 will be described. First, as shown in FIG. 9A, a first insulating film 261 is formed over a substrate 260. The first insulating film 261 is formed using a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or the like.
[0087]
In the case where a silicon oxide film is used, tetraethyl orthosilicate (TEOS) and O 2 are formed by plasma CVD. ₂ The reaction pressure is 40 Pa, the substrate temperature is 300 to 400 ° C., and the high frequency (13.56 MHz) power density is 0.5 to 0.8 W / cm. ² And can be formed by discharging. When a silicon oxynitride film is used, SiH is formed by plasma CVD. _Four , N ₂ O, NH _Three Silicon oxynitride film made from SiH or SiH _Four , N ₂ A silicon oxynitride film formed from O may be used. The production conditions in this case are a reaction pressure of 20 to 200 Pa, a substrate temperature of 300 to 400 ° C., and a high frequency (60 MHz) power density of 0.1 to 1.0 W / cm. ² Can be formed. SiH _Four , N ₂ O, H ₂ A silicon oxynitride silicon film manufactured from the above may be applied. Similarly, the silicon nitride film is formed by SiH by plasma CVD. _Four , NH _Three It is possible to make from.
[0088]
The first insulating film is formed to a thickness of 20 to 200 nm (preferably 30 to 60 nm) over the entire surface of the substrate, and then a mask 262 is formed using a photolithography technique as shown in FIG. 9B. Then, unnecessary portions are removed by etching, and a stripe-shaped or rectangular convex portion 263 is formed. For the first insulating film 261, a dry etching method using a fluorine-based gas may be used, or a wet etching method using a fluorine-based aqueous solution may be used. When the latter method is selected, for example, ammonium hydrogen fluoride (NH _Four HF ₂ ) 7.13% and ammonium fluoride (NH _Four F) may be etched with a mixed solution containing 15.4% (product name: LAL500, manufactured by Stella Chemifa).
[0089]
Next, a second insulating film 264 is formed so as to cover the convex portion 263 and the substrate 260. This layer is formed with a thickness of 50 to 300 nm (preferably 100 to 200 nm) using a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or the like, like the first insulating film 261.
[0090]
Through the manufacturing process, an insulating film including the convex portion 263 and the second insulating film 264 is formed. Note that after the second insulating film 264 is formed, impurities in the air are mixed between the semiconductor film and the insulating film by continuously forming the semiconductor film so as not to be exposed to the air. Can be prevented.
[0091]
(Example 2)
In this embodiment, after the semiconductor film formed on the stripe-shaped insulating film is crystallized by laser light irradiation, islands separated from each other are formed on a surface parallel to the substrate of the recess, and the islands are formed. An example in which a TFT is manufactured using the TFT will be described.
[0092]
FIG. 10A shows the structure of the TFT of this example. In FIG. 10A, an insulating film 152 having a stripe-shaped convex portion 151 is formed over a substrate 150. A plurality of islands 153 separated from each other are formed on the upper surface of the recesses between the protrusions 151. The plurality of islands 153 are formed using a portion of the semiconductor film between the vicinity of the edge of the recess and the vicinity of the center between the edges of the recess that is relatively difficult to form a grain boundary and has excellent crystallinity. . A gate insulating film 154 is formed so as to be in contact with the island 153. Note that although the gate insulating film 154 is formed so as to expose a portion to be an impurity region of the island in FIG. 10A, the gate insulating film 154 may be formed so as to cover the entire island 153.
[0093]
A plurality of gate electrodes 155 are formed on the gate insulating film 154 so as to overlap the plurality of islands 153. The plurality of gate electrodes 155 may be connected to each other depending on the circuit configuration.
[0094]
Note that a cross-sectional view taken along a line AA ′ in FIG. 10A corresponds to FIG. 10B, and a cross-sectional view taken along a line BB ′ in FIG. 10A corresponds to FIG. As shown in FIG. 10C, each gate electrode 155 overlaps with the channel formation region 156 of the island 153 with the gate insulating film 154 interposed therebetween. The channel formation region 156 is sandwiched between two impurity regions 157 that are also included in the island 153.
[0095]
In this embodiment, the TFT is formed using the island formed on the concave bottom portion, but the TFT may be formed using the island formed on the convex top portion.
[0096]
This embodiment can be implemented in combination with the first embodiment.
[0097]
(Example 3)
In this embodiment, variations in the shape of the insulating film will be described.
[0098]
FIG. 11A shows an example of the shape of the insulating film of the present invention. In FIG. 11A, an insulating film 171 is formed over a substrate 170, and the insulating film 171 has a plurality of convex portions 172. Each convex portion 172 has a rectangular shape as viewed from above. In all the convex portions, the long side direction or short side direction of the rectangle is parallel to the scanning direction of the laser beam indicated by the arrow.
[0099]
In addition, the widths of the convex portions 172 in the scanning direction of the laser light and the width in the direction perpendicular to the scanning direction are not all the same. It is desirable to design the shape of the insulating film in accordance with the desired island shape.
[0100]
Note that in the insulating film used in the present invention, the shape of the convex portion does not have to be completely rectangular or striped, and a part of the insulating film may be rectangular or striped. FIG. 11B shows an example of the shape of the insulating film of the present invention. In FIG. 11B, an insulating film 181 is formed over a substrate 180, and the insulating film 181 is formed with a rectangular convex portion 182 having a slit-like opening as viewed from above. The convex portion 182 has the long side direction or the short side direction of the slit parallel to the scanning direction of the laser beam indicated by the arrow.
[0101]
Next, an example of a structure of a TFT formed using an insulating film having a slit-like opening as shown in FIG. 11B will be described.
[0102]
FIG. 12A shows a top view of the TFT of this embodiment. As shown in FIG. 12A, in this embodiment, an insulating film having a rectangular convex portion 760 having a slit-like opening inside is used. A semiconductor film is formed so as to cover the convex portion 760, and laser light is scanned in the direction indicated by the arrow along the major axis direction of the slit-shaped opening to crystallize the semiconductor film. Then, the semiconductor film is patterned to form an island 761 having an opening in which a channel formation region is formed on the upper surface of the concave portion surrounded by the convex portion. Note that the channel formation region of the island 761 avoids the vicinity of the center between the edges of the recess, and uses a portion having excellent crystallinity between the vicinity of the edge of the recess and the vicinity of the center between the edges of the recess. To do.
[0103]
Then, a gate insulating film 762 is formed so as to be in contact with the island 761. 12A is a cross-sectional view taken along the line AA ′ in FIG. 12A, FIG. 12C is a cross-sectional view taken along the line BB ′, and FIG. 12D is a cross-sectional view taken along the line CC ′. ).
[0104]
A gate electrode 763 is formed by forming a conductive film over the gate insulating film 762 and patterning the conductive film. Note that the gate electrode 763 overlaps with the channel formation region 764 of the island 761 with the gate insulating film 762 interposed therebetween, and the channel formation region 764 is sandwiched between two impurity regions 765 included in the island 761.
[0105]
A first interlayer insulating film 766 is formed so as to cover the gate electrode 763, the island 761, and the gate insulating film 762. The first interlayer insulating film 766 is made of an inorganic insulating film and has an effect of preventing the island 761 from being mixed with a substance that adversely affects the characteristics of the TFT such as an alkali metal.
[0106]
Then, a second interlayer insulating film 767 made of an organic resin is formed on the first interlayer insulating film 766. The second interlayer insulating film 767, the first interlayer insulating film 766, and the gate insulating film 762 have openings formed by etching, and two impurity regions 765, a gate electrode 763, and the like are formed through the openings. Wirings 768 and 769 respectively connected to are formed on the second interlayer insulating film 767.
[0107]
In this embodiment, since a plurality of channel formation regions 764 are formed and the plurality of channel formation regions are separated from each other, the channel width of the channel formation region is increased to ensure the on-current, and the TFT The heat generated by driving can be efficiently radiated.
[0108]
In this embodiment, the TFT having the channel formation region formed in the concave bottom portion has been described. However, the TFT may be formed using the channel formation region formed in the convex top portion.
[0109]
Example 4
In this embodiment, a method for manufacturing an active matrix substrate using the laser crystallization method of the present invention will be described with reference to FIGS. In this specification, a substrate in which a pixel portion having a CMOS circuit, a driver circuit, a pixel TFT, and a storage capacitor is formed over the same substrate is referred to as an active matrix substrate for convenience.
[0110]
First, in this embodiment, a substrate 600 made of glass such as barium borosilicate glass or alumino borosilicate glass is used. Note that as the substrate 600, a quartz substrate, a silicon substrate, a metal substrate, or a stainless steel substrate on which an insulating film is formed may be used. Further, a plastic substrate having heat resistance that can withstand the processing temperature of this embodiment may be used.
[0111]
Next, an insulating film made of an insulating film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film is formed on the substrate 600 by a known means (sputtering method, LPCVD method, plasma CVD method, etc.) to a thickness of 100 to 300 nm. Form with.
[0112]
Next, in order to form a thick portion and a thin portion in this insulating film, in this embodiment, a resist mask 693 is formed by a photolithography technique, and an etching process is performed. Although the level difference is determined by the etching amount, in this embodiment, it is approximately 50 to 100 nm. For example, in order to etch a 150 nm silicon oxynitride film by 75 nm, wet etching using a solution containing hydrofluoric acid may be used, or CF _Four It is possible to apply dry etching or the like using In this manner, the insulating film 601 having a convex shape is formed. At this time, the width of the convex region in the direction perpendicular to the scanning direction of the laser beam may be appropriately determined in consideration of the size of the TFT to be manufactured. However, for the purpose of controlling the number of crystal nuclei generated, A size of about 6 μm (diameter or diagonal length) is preferable (FIG. 13A).
[0113]
Next, an amorphous semiconductor film 692 is formed on the insulating film 601 with a thickness of 25 to 80 nm (preferably 30 to 60 nm) by a known means (sputtering method, LPCVD method, plasma CVD method, or the like) (FIG. 13). (B)). Note that although an amorphous semiconductor film is formed in this embodiment, a microcrystalline semiconductor film or a crystalline semiconductor film may be used. Alternatively, a compound semiconductor film having an amorphous structure such as an amorphous silicon germanium film may be used.
[0114]
Next, the amorphous semiconductor film 692 is crystallized by a laser crystallization method. The scanning direction of the laser light is set to be parallel to the extending direction of the stripe-shaped convex portion in the insulating film 601. Note that in the case where the convex portion in the insulating film 601 is rectangular when viewed from above the substrate, the scanning direction of the laser light is determined so as to be parallel to the long side direction or the short side direction of the rectangle. Specifically, laser light is selectively irradiated according to mask information input to the computer of the laser irradiation apparatus. Of course, not only the laser crystallization method but also other known crystallization methods (thermal crystallization method using RTA or furnace annealing furnace, thermal crystallization method using metal element for promoting crystallization, etc.) You may go. Note that this embodiment shows an example in which the width of the laser beam is changed using a slit in accordance with the width in the direction perpendicular to the scanning direction of the insulating film, but the present invention is not limited to this, and the slit is not necessarily provided. There is no need to use it.
[0115]
When the amorphous semiconductor film is crystallized, a crystal having a large grain size can be obtained by using a solid-state laser capable of continuous oscillation and using the second to fourth harmonics of the fundamental wave. Typically, Nd: YVO _Four It is desirable to use the second harmonic (532 nm) or the third harmonic (355 nm) of the laser (fundamental wave 1064 nm). Specifically, continuous wave YVO _Four Laser light emitted from the laser is converted into a harmonic by a non-linear optical element to obtain laser light with an output of 10 W. Also, YVO in the resonator _Four There is also a method of emitting harmonics by inserting a crystal and a nonlinear optical element. Preferably, the laser beam is shaped into a rectangular or elliptical shape on the irradiation surface by an optical system, and the object to be processed is irradiated. The energy density at this time is 0.01 to 100 MW / cm. ² Degree (preferably 0.1-10 MW / cm ² )is required. Then, irradiation is performed by moving the semiconductor film relative to the laser light at a speed of about 10 to 2000 cm / s.
[0116]
Note that pulsed or continuous wave gas laser or solid-state laser can be used for laser irradiation. There are excimer laser, Ar laser, Kr laser, etc. as gas laser, and YAG laser, YVO as solid laser. _Four Laser, YLF laser, YAlO _Three Laser, glass laser, ruby laser, alexandride laser, Ti: sapphire laser, Y ₂ O _Three A laser etc. are mentioned. Solid lasers include YAG, YVO doped with Cr, Nd, Er, Ho, Ce, Co, Ti, Yb or Tm. _Four , YLF, YAlO _Three Lasers using crystals such as can also be used. A slab laser can also be used. The fundamental wave of the laser differs depending on the material to be doped, and a laser beam having a fundamental wave of about 1 μm can be obtained. The harmonic with respect to the fundamental wave can be obtained by using a nonlinear optical element.
[0117]
Through the above-described laser crystallization, a crystalline semiconductor film 694 with improved crystallinity is formed (FIG. 13C). In the crystalline semiconductor film, a grain boundary 695 is easily formed in the vicinity of the center between the edges.
[0118]
Next, the crystalline semiconductor film 694 with improved crystallinity is patterned into a desired shape to form crystallized islands 602 to 606 (FIG. 13D). At this time, the number of grain boundaries in the islands 602 to 606 can be reduced by removing the vicinity of the center between the edges where the grain boundaries 695 are easily formed.
[0119]
Further, after the islands 602 to 606 are formed, a small amount of impurity element (boron or phosphorus) may be doped in order to control the threshold value of the TFT.
[0120]
Next, a process of manufacturing a TFT using the islands 602 to 606 is performed. A specific manufacturing process of the TFT differs depending on the shape of the TFT, but typically, a gate insulating film is formed and an impurity region is formed in the island. Then, an interlayer insulating film is formed so as to cover the gate insulating film and the gate electrode, a contact hole is formed in the interlayer insulating film, and a part of the impurity region is exposed. Then, a wiring is formed on the interlayer insulating film so as to be in contact with the impurity region through the contact hole.
[0121]
FIG. 14 is a cross-sectional view of the semiconductor device of this example. The islands 602 to 606 include a channel formation region, a first impurity region that exists across the channel formation region, and a second impurity region formed between the first impurity region and the channel formation region. have. The concentration of the impurity imparting one conductivity type in the first impurity region is higher than that in the second impurity region. A gate insulating film 607 is formed to cover the islands 602 to 606, and gate electrodes 608 to 613 and a source signal line 614 are formed on the gate insulating film 607 so as to overlap the channel formation region. ing. Further, an interlayer insulating film 615 is formed over the gate insulating film 607 so as to cover the gate electrodes 608 to 613 and the source signal line 614.
[0122]
In the driving circuit 686, wirings 663 to 667 that are electrically connected to the impurity regions are formed over the interlayer insulating film 615. In the pixel portion 687, a pixel electrode 670, a gate wiring 669, and a wiring 668 are formed. The source signal line 614 is electrically connected to the pixel TFT 684 through the wiring 668.
[0123]
Although not shown, the gate wiring 669 is electrically connected to the gate electrodes 611 and 612 of the pixel TFT 684. In addition, the pixel electrode 670 is electrically connected to the first impurity region of the pixel TFT, and is further electrically connected to an island 606 that functions as one electrode forming the storage capacitor 685. In this application, the pixel electrode and the wiring are formed of the same material. However, a highly reflective material such as a film containing Al or Ag as a main component or a laminated film thereof may be used as the pixel electrode 670. .
[0124]
As described above, the CMOS circuit including the n-channel TFT 681 and the p-channel TFT 682, the driving circuit 686 having the n-channel TFT 683, and the pixel portion 687 having the pixel TFT 684 and the storage capacitor 685 are formed over the same substrate. can do. Thus, the active matrix substrate is completed. The storage capacitor 685 is formed of an electrode 613 and an island 606 using the gate insulating film 607 as a dielectric.
[0125]
In the pixel of this embodiment, the end portion of the pixel electrode overlaps with the source signal line so as to shield the gap between the pixel electrodes without using a shielding film.
[0126]
Note that although the structure of the active matrix substrate used in the liquid crystal display device is described in this embodiment, a light-emitting device can be manufactured using the manufacturing process of this embodiment. The light emitting device is a general term for a display panel in which a light emitting element formed on a substrate is sealed between the substrate and a cover material, and a display module in which a TFT or the like is mounted on the display panel. Note that the light-emitting element includes a layer (light-emitting layer) containing an organic compound from which luminescence (Electro Luminescence) generated by applying an electric field is obtained, an anode layer, and a cathode layer.
[0127]
Note that the light-emitting element has a mode in which a hole injection layer, an electron injection layer, a hole transport layer, an electron transport layer, or the like is formed of an inorganic compound alone or a material in which an inorganic compound is mixed with an organic compound. I can take it. These layers may be partially mixed with each other.
[0128]
Note that the present invention can also be applied to semiconductor devices in submicron units. In this embodiment, an example in which the active layer is formed in the concave bottom portion is shown. However, the active layer may be formed in the convex upper portion.
[0129]
This embodiment can be implemented in combination with the first to third embodiments.
[0130]
(Example 5)
In this embodiment, an example in which a laser light irradiation process and a semiconductor film crystallization process using a catalyst are combined in crystallization of a semiconductor film will be described. In the case of using a catalyst element, it is desirable to use the techniques disclosed in Japanese Patent Application Laid-Open Nos. 7-130652 and 8-78329.
[0131]
First, as illustrated in FIG. 15A, an insulating film 501 having a convex portion 502 is formed over a substrate 500. Then, a semiconductor film 503 is formed over the insulating film 501.
[0132]
Next, the semiconductor film 503 is crystallized using a catalyst element (FIG. 15B). For example, in the case of using the technique disclosed in Japanese Patent Laid-Open No. 7-130652, a nickel-containing layer 504 is formed by applying a nickel acetate salt solution containing 10 ppm of nickel in terms of weight to the semiconductor film 503, After the time dehydrogenation step, heat treatment is performed at 500 to 650 ° C. for 4 to 12 hours, for example, 550 ° C. for 8 hours, so that the semiconductor film 505 with improved crystallinity is formed. In addition to nickel (Ni), usable catalyst elements include germanium (Ge), iron (Fe), palladium (Pd), tin (Sn), lead (Pb), cobalt (Co), platinum ( Elements such as Pt), copper (Cu), and gold (Au) may be used.
[0133]
Then, a semiconductor film 506 with further improved crystallinity is formed from the semiconductor film 505 crystallized by NiSPC by laser light irradiation. The semiconductor film 506 obtained by laser light irradiation contains a catalytic element, and after the laser light irradiation, a step (gettering) of removing the catalytic element from the semiconductor film 506 is performed. For the gettering, a technique described in JP-A-10-135468 or JP-A-10-135469 can be used.
[0134]
Specifically, a region 507 in which phosphorus is added to part of the semiconductor film 506 obtained after laser irradiation is formed. Heat treatment is performed in a nitrogen atmosphere at 550 to 800 ° C. for 5 to 24 hours, for example, 600 ° C. for 12 hours. Then, the region 507 to which phosphorus is added in the semiconductor film 506 functions as a gettering site, and the catalytic element present in the semiconductor film 506 can be segregated to the region 507 to which phosphorus is added (FIG. 15D). ).
[0135]
Thereafter, the concentration of the catalytic element is set to 1 × 10 by removing the phosphorus-added region 507 of the semiconductor film 506 by patterning. ¹⁷ atoms / cm ^Three Preferably 1 × 10 ¹⁶ atoms / cm ^Three An island 508 reduced to an extent can be obtained (FIG. 15E).
[0136]
Note that after applying a solution containing a catalytic element to the semiconductor film before crystallization, crystal growth may be performed by laser light irradiation instead of SPC.
[0137]
This embodiment can be implemented in combination with the first to fourth embodiments.
[0138]
(Example 6)
In this embodiment, the shape of a laser beam synthesized by superposing a plurality of laser beams will be described.
[0139]
FIG. 16A shows an example of the shape of the laser beam on the object to be processed when the laser light emitted from each of the plurality of laser oscillation devices does not pass through the slit. The laser beam shown in FIG. 16A has an elliptical shape. In the present invention, the shape of the laser beam of the laser light oscillated from the laser oscillation device is not limited to an ellipse. The shape of the laser beam varies depending on the type of laser and can also be shaped by an optical system. For example, the shape of a laser beam emitted from a Lambda XeCl excimer laser (wavelength 308 nm, pulse width 30 ns) L3308 is a rectangular shape of 10 mm × 30 mm (both half-value width in the beam profile). The shape of the laser light emitted from the YAG laser is circular if the rod shape is cylindrical, and rectangular if it is slab type. By further shaping such laser light with an optical system, laser light of a desired size can be produced.
[0140]
FIG. 16B shows the energy density distribution of the laser light in the long axis Y direction of the laser beam shown in FIG. The laser beam shown in FIG. 16A is 1 / e of the peak value of the energy density in FIG. ² This corresponds to a region satisfying the energy density of. The energy density distribution of the laser beam having the elliptical laser beam becomes higher toward the center O of the ellipse. As described above, in the laser beam shown in FIG. 16A, the energy density in the central axis direction follows a Gaussian distribution, and a region where it can be determined that the energy density is uniform becomes narrow.
[0141]
Next, FIG. 16C illustrates the shape of a laser beam when the laser light having the laser beam illustrated in FIG. Note that FIG. 16C illustrates the case where one linear laser beam is formed by superimposing four laser beams, but the number of superposed laser beams is not limited thereto.
[0142]
As shown in FIG. 16C, the laser beams of the respective laser beams are synthesized by matching the major axes of the respective ellipses and overlapping a part of the laser beams to form one laser beam 360. Yes. Hereinafter, a straight line obtained by connecting the centers O of the ellipses will be referred to as a central axis of the laser beam 360.
[0143]
FIG. 16D shows the energy density distribution of the laser beam in the direction of the central axis y of the combined laser beam shown in FIG. Note that the laser beam illustrated in FIG. 16C is 1 / e of the peak value of the energy density in FIG. ² This corresponds to a region satisfying the energy density of. The energy density is added at the portion where the laser beams before synthesis are overlapped. For example, when the energy densities E1 and E2 of the overlapping beams are added as shown in the figure, the energy density peak value E3 is approximately equal, and the energy density is flattened between the centers O of the ellipses.
[0144]
Note that when E1 and E2 are added, it is ideally equal to E3, but in reality, it is not necessarily equal. The allowable range of deviation between the value obtained by adding E1 and E2 and the value of E3 can be appropriately set by the designer.
[0145]
When the laser beam is used alone, the energy density distribution follows a Gaussian distribution, so that the entire semiconductor film or island part in contact with the flat part of the insulating film can be irradiated with laser light with a uniform energy density. difficult. However, as can be seen from FIG. 16D, by superimposing a plurality of laser beams and complementing each other with a low energy density, energy can be obtained rather than using a plurality of laser beams without overlapping. A region having a uniform density is enlarged, and the crystallinity of the semiconductor film can be increased efficiently.
[0146]
FIG. 17 shows the distribution of energy density at BB ′ and CC ′ in FIG. 16C obtained by calculation. FIG. 17 shows 1 / e of the peak value of the laser beam before synthesis. ² The region that satisfies the energy density is used as a reference. The energy density at BB ′ and CC ′ when the length in the minor axis direction of the laser beam before synthesis is 37 μm, the length in the major axis direction is 410 μm, and the distance between the centers is 192 μm is The distributions are as shown in FIGS. 17A and 17B, respectively. Although BB ′ is weaker than CC ′, it can be regarded as almost the same size, and is 1 / e of the peak value of the laser beam before synthesis. ² The shape of the combined laser beam in the region satisfying the energy density can be expressed as a linear shape.
[0147]
FIG. 18A is a diagram showing the energy distribution of the combined laser beam. A region indicated by 361 is a region having a uniform energy density, and a region indicated by 362 is a region having a low energy density. In FIG. 18, the length of the laser beam in the direction of the central axis is W _TBW And the length in the central axis direction in the region 361 having a uniform energy density is W _max And W _TBW Is W _max The larger the ratio is, the larger the ratio of the region 362 having a non-uniform energy density that cannot be used for crystallization of the semiconductor film to the region 361 having a uniform energy density that can be used for crystallization. In the semiconductor film irradiated only with the region 362 where the energy density is not uniform, crystallites are generated and the crystallinity is not good. Therefore, it is necessary to determine the layout of the scanning path and the unevenness of the insulating film so that only the region 362 does not overlap with the region to be the island of the semiconductor film, and the restriction becomes even greater as the ratio of the region 362 to the region 361 increases. . Therefore, using the slits to prevent the semiconductor film formed on the concave portion or the convex portion of the insulating film from being irradiated only with the region 362 where the energy density is not uniform can prevent the layout of the scanning path and the concave and convex portions of the insulating film. This is effective in reducing the constraints that occur in the process.
[0148]
This embodiment can be implemented in combination with the first to fifth embodiments.
[0149]
(Example 7)
In this embodiment, the optical system of the laser irradiation apparatus used in the present invention and the positional relationship between each optical system and the slit will be described.
[0150]
FIG. 19 shows an optical system in the case where four laser beams are combined into one laser beam. The optical system shown in FIG. 19 has six cylindrical lenses 417 to 422. The four laser beams incident from the direction of the arrows are incident on the four cylindrical lenses 419 to 422, respectively. The two laser beams molded by the cylindrical lenses 419 and 421 are shaped again by the cylindrical lens 417 and irradiated to the object 423 through the slit 424. On the other hand, the two laser beams formed by the cylindrical lenses 420 and 422 are shaped again by the cylindrical lens 418 and irradiated to the object 423 through the slit 424.
[0151]
The laser beams of the respective laser beams on the object to be processed 423 are combined by overlapping each other to form one laser beam.
[0152]
The focal length and incident angle of each lens can be appropriately set by the designer, but the focal lengths of the cylindrical lenses 417 and 418 closest to the object 423 are smaller than the focal lengths of the cylindrical lenses 419 to 422. To do. For example, the focal lengths of the cylindrical lenses 417 and 418 closest to the object to be processed 423 are set to 20 mm, and the focal lengths of the cylindrical lenses 419 to 422 are set to 150 mm. In this embodiment, the incident angle of laser light from the cylindrical lenses 417 and 418 to the object 423 is 25 °, and the incident angle of laser light from the cylindrical lenses 419 to 422 to the cylindrical lenses 417 and 418 is 10 °. Install each lens as you want. In order to prevent return light and perform uniform irradiation, it is desirable to keep the incident angle of the laser light on the substrate larger than 0 °, preferably 5 to 30 °.
[0153]
FIG. 19 shows an example of synthesizing four laser beams. In this case, there are four cylindrical lenses respectively corresponding to the four laser oscillation devices and two cylindrical lenses corresponding to the four cylindrical lenses. ing. The number of laser beams to be combined is not limited to this, and the number of laser beams to be combined may be 2 or more and 8 or less. When synthesizing n (n = 2, 4, 6, 8) laser beams, n cylindrical lenses corresponding to the n laser oscillation devices, and n / 2 cylindrical lenses corresponding to the n cylindrical lenses, have. When synthesizing n (n = 3, 5, 7) laser beams, n cylindrical lenses respectively corresponding to the n laser oscillation devices, and (n + 1) / 2 cylindrical lenses corresponding to the n cylindrical lenses, have.
[0154]
Then, when superposing five or more laser beams, considering the place where the optical system is arranged and interference, it is desirable to irradiate the fifth and subsequent laser beams from the opposite side of the substrate. It must also be provided on the opposite side. Further, the substrate needs to have transparency.
[0155]
In order to prevent the return light from returning along the original optical path, it is desirable to keep the incident angle with respect to the substrate larger than 0 and smaller than 90 °.
[0156]
Also, in order to realize uniform laser light irradiation, a plane or long side that is a plane perpendicular to the irradiation surface and includes a short side when the shape of each beam before synthesis is regarded as a rectangle is obtained. If any one of the surfaces to be included is defined as an incident surface, the incident angle θ of the laser light is set such that the length of the short side or the long side included in the incident surface is W, and is set on the irradiation surface, and It is desirable that θ ≧ arctan (W / 2d) is satisfied when the thickness of the substrate having translucency with respect to the laser beam is d. This argument needs to hold for each laser beam before synthesis. When the locus of the laser beam is not on the incident surface, the incident angle obtained by projecting the locus onto the incident surface is defined as θ. If the laser light is incident at this incident angle θ, the reflected light from the surface of the substrate and the reflected light from the back surface of the substrate do not interfere with each other, and uniform laser light irradiation can be performed. In the above discussion, the refractive index of the substrate was considered as 1. Actually, in many cases, the refractive index of the substrate is around 1.5, and if this value is taken into consideration, a calculated value larger than the angle calculated in the above discussion can be obtained. However, since the energy at both ends in the longitudinal direction of the beam spot is attenuated, the influence of interference in this portion is small, and the effect of interference attenuation can be sufficiently obtained with the above calculated value. The above inequality for θ does not apply to anything other than the substrate being translucent to the laser beam.
[0157]
The optical system of the laser irradiation device used in the present invention is
The configuration is not limited to the example shown.
[0158]
This embodiment can be implemented in combination with the first to sixth embodiments.
[0159]
(Example 8)
A laser beam having an elliptical laser beam has a Gaussian distribution of energy density in a direction perpendicular to the scanning direction. Therefore, a laser beam having a rectangular or linear laser beam accounts for the ratio of the low energy density region to the entire region. Higher than light. Therefore, in the present invention, it is desirable that the laser beam of the laser beam is rectangular or linear with a relatively uniform energy density distribution.
[0160]
A typical gas laser capable of obtaining a rectangular or linear laser beam is an excimer laser, and a typical solid laser is a slab laser. In this embodiment, a slab laser will be described.
[0161]
FIG. 20A illustrates an example of a structure of a slab type laser oscillation device. A slab type laser oscillation device shown in FIG. 20A includes a rod 7500, a reflection mirror 7501, an exit mirror 7502, and a cylindrical lens 7503.
[0162]
When the rod 7500 is irradiated with excitation light, a laser beam is emitted toward the reflection mirror 7501 or the emission mirror 7502 along the zigzag optical path in the rod 7500. The laser beam emitted to the reflection mirror 7501 side is reflected, enters the rod 7500 again, and is emitted to the emission mirror 7502 side. The rod 7500 is a slab type using a plate-like slab medium, and can form a relatively long rectangular or linear laser beam in the emission stage. Then, the emitted laser light is processed in a cylindrical lens 7503 so that the shape of the laser beam becomes thinner and emitted from the laser oscillation device.
[0163]
Next, FIG. 20B illustrates a structure of the slab type laser oscillation device which is different from that illustrated in FIG. In FIG. 20B, a cylindrical lens 7504 is added to the laser oscillation apparatus illustrated in FIG. 20A, and the length of the laser beam can be controlled by the cylindrical lens 7504.
[0164]
If the coherent length is 10 cm or more, preferably 1 m or more, the laser beam can be made thinner.
[0165]
In order to prevent the temperature of the rod 7500 from rising excessively, a means for controlling the temperature, for example, circulating cooling water may be provided.
[0166]
FIG. 20C shows an example of the shape of a cylindrical lens. Reference numeral 7509 denotes a cylindrical lens of this embodiment, which is fixed by a holder 7510. The cylindrical lens 7509 has a shape in which a cylindrical surface and a rectangular plane face each other, and the two bus bars of the cylindrical surface and the two opposite rectangular sides are all parallel to each other. Two surfaces formed by the two generatrices of the cylindrical surface and the two parallel sides intersect each other at an angle larger than 0 and smaller than 90 °. The two surfaces formed by the two parallel sides in this way intersect with the rectangular plane at an angle of less than 90 °, so that the focal length can be shortened compared to the case of 90 ° or more. It is possible to make the shape of the laser beam narrower and approximate to the linear shape.
[0167]
This embodiment can be implemented in combination with the first to seventh embodiments.
[0168]
Example 9
In this embodiment, the relationship between the distance between the centers of laser beams and the energy density when the laser beams are superimposed will be described.
[0169]
FIG. 21 shows the energy density distribution in the central axis direction of each laser beam by a solid line, and the energy density distribution of the synthesized laser beam by a broken line. The value of the energy density in the direction of the central axis of the laser beam generally follows a Gaussian distribution.
[0170]
1 / e of peak value in laser beam before synthesis ² Let X be the distance between the peaks when the distance in the central axis direction satisfying the above energy density is 1. In the combined beam spot, Y is the percent increment of the peak value after the combination and the average value of the valley values. The relationship between X and Y obtained by simulation is shown in FIG. In FIG. 22, Y is expressed as a percentage.
[0171]
In FIG. 22, the energy difference Y is expressed by the following approximate expression of Expression 1.
[0172]
[Formula 1]
Y = 60-293X + 340X ² (X is the larger of the two solutions)
[0173]
According to Equation 1, for example, when it is desired to make the energy difference about 5%, it can be understood that X≈0.584. Ideally, Y = 0. However, since the length of the beam spot is shortened, it is preferable to determine X in balance with the throughput.
[0174]
Next, the allowable range of Y will be described. FIG. 23 shows YVO with respect to the beam width in the central axis direction when the laser beam has an elliptical shape. _Four The distribution of laser output (W) is shown. The region indicated by hatching is the range of output energy necessary for obtaining good crystallinity, and it is understood that the output energy of the synthesized laser beam is within the range of 3.5 to 6 W.
[0175]
When the maximum value and the minimum value of the output energy of the beam spot after synthesis enter the limit of the output energy range necessary for obtaining good crystallinity, the energy difference Y for obtaining good crystallinity is maximized. Therefore, in the case of FIG. 23, the energy difference Y is ± 26.3%, and it can be seen that good crystallinity can be obtained if the energy difference Y is within the above range.
[0176]
Note that the range of output energy required to obtain good crystallinity varies depending on how far the crystallinity is judged to be good, and the distribution of output energy also varies depending on the shape of the laser beam. The allowable range of Y is not necessarily limited to the above value. The designer needs to appropriately determine the range of output energy necessary for obtaining good crystallinity, and set the allowable range of the energy difference Y from the distribution of the output energy of the laser used.
[0177]
This example can be implemented in combination with Examples 1-8.
[0178]
(Example 10)
The present invention can be applied to various semiconductor devices, and the mode of a display panel manufactured based on Examples 1 to 9 will be described with reference to FIGS.
[0179]
24, a substrate 901 includes a pixel portion 902, gate signal side driver circuits 901a and 901b, a data signal side driver circuit 901c, an input / output terminal portion 908, and a wiring or a wiring group 904. The shield pattern 905 may partially overlap with the gate signal side driving circuits 901a and 901b, the data signal side driving circuit 901c, and the wiring or wiring group 904 that connects the driving circuit portion and the input / output terminal portion 908. In this way, the area of the frame region (the peripheral region of the pixel portion) of the display panel can be reduced. An FPC 903 is fixed to the input / output terminal portion 908.
[0180]
The present invention can be used for active elements constituting the pixel portion 902, the gate signal side driver circuits 901a and 901b, and the data signal side driver circuit 901c.
[0181]
FIG. 25 shows an example of the structure of one pixel of the pixel portion 902 shown in FIG. 24, and TFTs 801 to 803 are provided. These are switching TFTs, reset TFTs, and driving TFTs for controlling light emitting elements and liquid crystal elements included in the pixels.
[0182]
The active layers 812 to 814 of these TFTs are disposed between the edges of the recesses 810 and 811 of the insulating film formed in the lower layer and the vicinity of the center between the edges. Over the active layers 812 to 814, gate wirings 815 to 817 are formed, and a data line 819, a power supply line 820, other various wirings 821 and 822, and a pixel electrode 823 are formed through a passivation film and a planarization film. ing.
[0183]
In this embodiment, the TFT is formed using the island formed on the concave bottom portion, but the TFT may be formed using the island formed on the convex top portion.
[0184]
This embodiment can be implemented in combination with any of Embodiments 1 to 9.
[0185]
(Example 11)
A semiconductor device including a TFT manufactured using the present invention can be applied to various electronic devices. Examples thereof include portable information terminals (electronic notebooks, mobile computers, mobile phones, etc.), video cameras, digital cameras, personal computers, television receivers, mobile phones, projection display devices, and the like. Specific examples of these electronic devices are shown in FIGS.
[0186]
FIG. 26A illustrates a display device, which includes a housing 2001, a support base 2002, a display portion 2003, a speaker portion 2004, a video input terminal 2005, and the like. By using the semiconductor device of the present invention for the display portion 2003, the display device of the present invention is completed. Since the light-emitting device is a self-luminous type, a backlight is not necessary and a display portion thinner than a liquid crystal display can be obtained. The display devices include all information display devices for personal computers, for receiving TV broadcasts, for displaying advertisements, and the like.
[0187]
FIG. 26B shows a digital still camera, which includes a main body 2101, a display portion 2102, an image receiving portion 2103, operation keys 2104, an external connection port 2105, a shutter 2106, and the like. By using the semiconductor device of the present invention for the display portion 2102, the digital still camera of the present invention is completed.
[0188]
FIG. 26C illustrates a laptop personal computer, which includes a main body 2201, a housing 2202, a display portion 2203, a keyboard 2204, an external connection port 2205, a pointing mouse 2206, and the like. By using the semiconductor device of the present invention for the display portion 2203, the notebook personal computer of the present invention is completed.
[0189]
FIG. 26D illustrates a mobile computer, which includes a main body 2301, a display portion 2302, a switch 2303, operation keys 2304, an infrared port 2305, and the like. By using the semiconductor device of the present invention for the display portion 2302, the mobile computer of the present invention is completed.
[0190]
FIG. 26E shows a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 2401, a housing 2402, a display portion A 2403, a display portion B 2404, and a recording medium (DVD or the like). A reading unit 2405, operation keys 2406, a speaker unit 2407, and the like are included. A display portion A2403 mainly displays image information, and a display portion B2404 mainly displays character information. Note that an image reproducing device provided with a recording medium includes a home game machine and the like. By using the semiconductor device of the present invention for the display portions A, B 2403 and 2404, the image reproducing device of the present invention is completed.
[0191]
FIG. 26F illustrates a goggle type display (head mounted display), which includes a main body 2501, a display portion 2502, and an arm portion 2503. By using the semiconductor device of the present invention for the display portion 2502, the goggle type display of the present invention is completed.
[0192]
FIG. 26G illustrates a video camera, which includes a main body 2601, a display portion 2602, a housing 2603, an external connection port 2604, a remote control reception portion 2605, an image receiving portion 2606, a battery 2607, an audio input portion 2608, operation keys 2609, and an eyepiece. Part 2610 and the like. By using the semiconductor device of the present invention for the display portion 2602, the video camera of the present invention is completed.
[0193]
FIG. 26H shows a cellular phone, which includes a main body 2701, a housing 2702, a display portion 2703, an audio input portion 2704, an audio output portion 2705, operation keys 2706, an external connection port 2707, an antenna 2708, and the like. Note that the display portion 2703 can suppress current consumption of the mobile phone by displaying white characters on a black background. By using the semiconductor device of the present invention for the display portion 2703, the cellular phone of the present invention is completed.
[0194]
As described above, the applicable range of the present invention is so wide that it can be used for electronic devices in various fields. In addition, this embodiment can be implemented in combination with any of the configurations shown in Embodiments 1 to 10.
[0195]
(Example 12)
In this embodiment, a structure of a semiconductor device of the present invention will be described. FIG. 27 shows a cross-sectional view of the semiconductor device of this example.
[0196]
A first insulating film 701 having convex portions 701 a and 701 b is formed over the substrate 700. A first TFT 702 is formed over the first insulating film 701. Note that the island of the first TFT 702 is formed on the first insulating film 701 between the edge of the recess formed by the protrusions 701a and 701b and the vicinity of the center between the edges.
[0197]
A first interlayer insulating film 703 is formed so as to cover the first TFT 702, and is electrically connected to the first connection wiring 705 and the first TFT 702 on the first interlayer insulating film 703. Wiring 704 is formed.
[0198]
A second interlayer insulating film 706 is formed so as to cover the wiring 704 and the first connection wiring 705. The second interlayer insulating film 706 is formed of an inorganic insulating film, and if the upper surface thereof is polished by a chemical mechanical polishing method (CMP method), the second insulating film to be formed later becomes more When a semiconductor film which is planarized and formed over the second insulating film is crystallized with laser light, the crystallinity can be further increased.
[0199]
A second insulating film 707 is formed on the second interlayer insulating film 706. The second insulating film 707 has a convex portion 707a. A second TFT 708 is formed over the second insulating film 707. Note that the island of the second TFT 708 is formed on the second insulating film 707 between the edge of the concave portion formed by the convex portion 707a and the vicinity of the center between the edge and the other edge (not shown). Is formed.
[0200]
A third interlayer insulating film 709 is formed so as to cover the second TFT 708, and is electrically connected to the second connection wiring 711 and the second TFT 708 on the third interlayer insulating film 709. Wiring 710 is formed. Note that a buried wiring (plug) 712 is formed between the first connection wiring 705 and the second connection wiring 711 by a damascene process or the like.
[0201]
A fourth interlayer insulating film 713 is formed so as to cover the wiring 710 and the second connection wiring 711.
[0202]
In this embodiment, a so-called stack structure in which the first TFT 702 and the second TFT 708 can be stacked with an interlayer insulating film interposed therebetween. Using the TFT having the stack structure of this embodiment, a CPU using LSI, a memory element (for example, SRAM) of various logic circuits, a counter circuit, a frequency divider circuit logic, and the like can be formed.
[0203]
In this embodiment, the TFT is formed using the island formed on the concave bottom portion, but the TFT may be formed using the island formed on the convex top portion.
[0204]
This embodiment can be implemented by freely combining with Embodiments 1 to 11.
[0205]
(Example 13)
In this embodiment, energy density distribution in a linear laser beam formed by combining a plurality of elliptical laser beams will be described.
[0206]
FIG. 28 shows 1 / e when two elliptical laser beams having a major axis of 400 μm and a minor axis of 40 μm are superimposed. ² The distribution of energy density in width is shown. All numbers in the graph are expressed in units of mm. The distance between the centers of adjacent beams is 0.255 mm.
[0207]
FIG. 29 shows 1 / e when four elliptical laser beams having a major axis of 400 μm and a minor axis of 40 μm are superimposed. ² The distribution of energy density in width is shown. All numbers in the graph are expressed in units of mm. The distance between the centers of adjacent beams is 0.255 mm.
[0208]
FIG. 30 shows 1 / e when four elliptical laser beams having a major axis of 400 μm and a minor axis of 40 μm are superimposed. ² The distribution of energy density in width is shown. All numbers in the graph are expressed in units of mm. The distance between the centers of adjacent beams is 0.215 mm.
[0209]
In an elliptical laser beam, the energy density distribution in the center line direction follows a Gaussian distribution. On the other hand, a laser beam formed by superimposing a plurality of elliptical laser beams has an energy density distribution in the center line direction of a certain height or more, as shown in FIGS. Unlike an elliptical laser beam, it has a waveform, and it can be said that the energy density in the center line direction is relatively uniform and linear.
[0210]
By applying a laser beam having such a linear energy distribution to the present invention, an island having uniform crystallinity can be formed.
[0211]
This embodiment can be implemented by freely combining with Embodiments 1 to 12.
[0212]
(Example 14)
In this embodiment, the concentration of oxygen, nitrogen, carbon, and boron incorporated in a semiconductor film by irradiation with continuous wave laser light will be described.
[0213]
First, an amorphous silicon film is formed on an insulating film made of silicon oxynitride to a thickness of 1500 mm, a nickel acetate salt solution is applied to the amorphous silicon film, and heated at 500 to 650 ° C. Thereafter, crystallization is performed using a continuous wave laser beam to form a crystalline silicon film (poly-Si). The laser beam irradiation was performed in an air atmosphere in a clean room. A naturally thin oxide film (natural oxide film) is formed on the surface of the crystalline silicon film. Then, an amorphous silicon film is formed covering the crystalline silicon film and the thin natural oxide film.
[0214]
In this state, oxygen, nitrogen, carbon, and boron atomic concentration profiles measured by secondary ion mass spectrometry (SIMS) are shown in FIGS.
[0215]
FIG. 31 shows a profile of oxygen concentration in a crystalline or amorphous silicon film measured by SIMS. The vertical axis represents the atomic concentration of oxygen, and the horizontal axis represents the depth from the sample surface. The solid line is the oxygen concentration when the process of irradiating laser light is performed, and the broken line is the oxygen concentration when the process of irradiating laser light is not performed. In addition, the ionic strength of silicon with the horizontal axis as the depth from the sample surface is also shown. The concentration of oxygen after laser light irradiation is 2 × 10 ¹⁹ atoms / cm ^Three It is as follows. As shown in FIG. 31, it can be seen that the oxygen concentration in the silicon film was increased by the laser light irradiation.
[0216]
FIG. 32 shows a profile of nitrogen concentration in a crystalline or amorphous silicon film measured by SIMS. The vertical axis represents the atomic concentration of nitrogen, and the horizontal axis represents the depth from the sample surface. The solid line indicates the nitrogen concentration when the process of irradiating laser light is performed, and the broken line indicates the nitrogen concentration when the process of irradiating laser light is not performed. In addition, the ionic strength of silicon with the horizontal axis as the depth from the sample surface is also shown. The concentration of nitrogen after laser light irradiation is 1 × 10 ¹⁹ atoms / cm ^Three It is as follows. As shown in FIG. 32, it can be seen that the nitrogen concentration in the silicon film was increased by the laser light irradiation.
[0217]
FIG. 33 shows a profile of the carbon concentration in the crystalline or amorphous silicon film measured by SIMS. The vertical axis represents the atomic concentration of carbon, and the horizontal axis represents the depth from the sample surface. The solid line indicates the carbon concentration when the process of irradiating laser light is performed, and the broken line indicates the carbon concentration when the process of irradiating laser light is not performed. In addition, the ionic strength of silicon with the horizontal axis as the depth from the sample surface is also shown. The concentration of carbon after laser light irradiation is 5 × 10 ¹⁸ atoms / cm ^Three It is as follows. As shown in FIG. 33, it can be seen that the carbon concentration in the silicon film was increased by the laser light irradiation.
[0218]
FIG. 34 shows a profile of boron concentration in a crystalline or amorphous silicon film measured by SIMS. The vertical axis represents the atomic concentration of boron, and the horizontal axis represents the depth from the sample surface. The solid line is the boron concentration when the process of irradiating laser light is performed, and the broken line is the boron concentration when the process of irradiating laser light is not performed. In addition, the ionic strength of silicon with the horizontal axis as the depth from the sample surface is also shown. From FIG. 34, it seems that the boron concentration in the silicon film is slightly increased by laser light irradiation, but in any case, it is below the minimum concentration measured by SIMS before and after laser irradiation, Very small amount.
[0219]
(Example 15)
In this embodiment, the relationship between the shape of an insulating film and the thickness of a semiconductor film formed thereon is described.
[0220]
FIG. 35A shows an insulating film 950 having a convex portion 950a and a semiconductor film 951 formed thereon. Note that the semiconductor film 951 shows a state after being crystallized by laser light.
[0221]
As shown in FIG. 35A, the film thickness Ht of the semiconductor film 951 located on the protrusions 950a is thinner than the film thickness Hb of the semiconductor film 951 located on the recesses between the protrusions 950a. Yes. This is presumably because the semiconductor film that was primarily dissolved by the irradiation of the laser beam moves to the recess. Therefore, it is considered that the surface of the semiconductor film 951 may be planarized to some extent after the laser light irradiation.
[0222]
FIG. 35B shows an insulating film 960 having a convex portion 960a and a semiconductor film 961 having a flat surface formed thereon. In FIG. 35A, unevenness is also formed on the surface of the semiconductor film 951. However, in FIG. 35B, the unevenness is flattened by laser light irradiation.
[0223]
FIG. 35C is a cross-sectional view of the insulating film in which the width Wt of the convex portion is wider than the width Wb of the concave portion in a direction perpendicular to the scanning direction of the laser beam. When a portion having excellent crystallinity of the semiconductor film located on the convex portion is used as the active layer of the TFT, the width Wt of the convex portion becomes wider than the width Wb of the concave portion as shown in FIG. It is preferable that there is less restriction on the island layout.
[0224]
This embodiment can be implemented by freely combining with Embodiments 1 to 14.
[0225]
【The invention's effect】
In the present invention, after crystallization by laser light, the vicinity of the center between the edges of the recesses or protrusions of the semiconductor film is removed by patterning, and the vicinity of the edges of the recesses or protrusions and the center between the edges of the recesses or protrusions are removed. Preventing the formation of grain boundaries in the channel formation region of the TFT by actively using as the active layer of the TFT the part where the grain boundary is relatively difficult to form and the crystallinity is excellent. Therefore, it is possible to prevent the mobility of the TFT from being significantly lowered by the grain boundary, the ON current from being reduced, and the OFF current from being increased. It should be noted that the designer can appropriately determine the extent to be removed by patterning as the vicinity of the edge of the concave portion or convex portion.
[0226]
In addition, the entire semiconductor film is not scanned and irradiated, but the laser beam is scanned so that at least an indispensable portion can be crystallized at a minimum. With the above structure, it is possible to omit the time for irradiating a portion of the semiconductor film that is removed by patterning after crystallization, and to significantly reduce the processing time per substrate.
[0227]
Also, by superimposing a plurality of laser beams and complementing each other with low energy density portions, the crystallinity of the semiconductor film can be improved more efficiently than using a plurality of laser beams alone without overlapping. it can.
[0228]
Instead of forming irregularities in the insulating film, the positions of the grain boundaries of the semiconductor film formed thereon may be controlled by providing irregularities in the substrate itself by etching.
[Brief description of the drawings]
FIG. 1 is a diagram showing the direction of crystal growth in a semiconductor film when irradiated with laser light.
FIG. 2 shows a state in which a semiconductor film is irradiated with laser light
FIG. 3 is a diagram of an island formed by patterning a crystallized semiconductor film.
4 is a diagram showing a structure of a TFT formed using the island shown in FIG. 3;
FIG. 5 shows a flowchart of the production system of the present invention.
FIG. 6 is a diagram of a laser irradiation apparatus.
FIG. 7 is a diagram of a laser irradiation apparatus.
8A and 8B illustrate a method for manufacturing an insulating film having unevenness.
9A and 9B illustrate a method for manufacturing an insulating film having unevenness.
FIG. 10 is a diagram of a TFT formed using islands that are separated from each other.
FIG. 11 shows a shape of an insulating film having unevenness.
12A and 12B are a top view and a cross-sectional view of a TFT formed using the insulating film illustrated in FIG.
FIGS. 13A to 13C illustrate a method for manufacturing a semiconductor device using the present invention. FIGS.
FIGS. 14A to 14C illustrate a method for manufacturing a semiconductor device using the present invention. FIGS.
FIG. 15 is a diagram showing a method for crystallizing a semiconductor film using a catalytic metal.
FIG. 16 is a diagram showing a distribution of energy density of a laser beam.
FIG. 17 is a diagram showing a distribution of energy density of a laser beam.
FIG. 18 is a diagram showing a distribution of energy density of a laser beam.
FIG. 19 is a diagram of an optical system.
FIG. 20 is a diagram of an optical system.
FIG. 21 is a graph showing the energy density distribution in the direction of the central axis of superimposed laser beams.
FIG. 22 is a diagram showing the relationship between the distance between the centers of laser beams and the energy difference.
FIG. 23 is a diagram showing a distribution of output energy in the direction of the central axis of a laser beam.
FIG 24 illustrates a structure of a light-emitting device which is an example of a semiconductor device of the invention.
FIG 25 illustrates a structure of a pixel of a light-emitting device that is an example of a semiconductor device of the invention.
FIG. 26 is a diagram of an electronic device using a semiconductor device of the invention.
FIG. 27 is a cross-sectional view of a TFT having a stack structure.
FIG. 28 is a diagram showing an energy density distribution of a laser beam obtained by combining two laser beams.
FIG. 29 is a diagram showing an energy density distribution of a laser beam obtained by synthesizing four laser beams.
FIG. 30 is a diagram showing an energy density distribution of a laser beam obtained by synthesizing four laser beams.
FIG. 31 is a profile of oxygen concentration in a silicon film crystallized by laser light.
FIG. 32 is a profile of nitrogen concentration in a silicon film crystallized by laser light.
FIG. 33 is a profile of carbon concentration in a silicon film crystallized by laser light.
FIG. 34 shows a boron concentration profile in a silicon film crystallized by laser light.
FIG. 35 is a cross-sectional view of an insulating film having unevenness and a semiconductor film formed thereover;

Claims (21)

An insulating film having a plurality of rectangular or striped irregularities;
Wherein the insulating film, and a thin film transistor using a crystalline semiconductor film having a plurality of channel formation region provided on between each of the edge near the center and the plurality of concave bottom portions of each of the plurality of recessed bottom,
A semiconductor device comprising:
It said plurality of channel formation regions are isolated from each other, yet, is located between the source and drain regions in which the plurality of the crystalline semiconductor film provided over a respective recessed bottom part has,
Each of the plurality of switch Yaneru forming region, wherein a extending along the longitudinal direction of the rectangular or stripe-shaped irregularities. An insulating film having a plurality of rectangular or striped irregularities;
Wherein the insulating film, and a thin film transistor using a crystalline semiconductor film having a plurality of channel formation region provided on between each of the edge near the center and the plurality of concave bottom portions of each of the plurality of recessed bottom,
A semiconductor device comprising:
It said plurality of channel formation regions are isolated from each other, yet, is located between the source and drain regions in which the plurality of the crystalline semiconductor film provided over a respective recessed bottom part has,
Each of the plurality of switch Yaneru forming region, wherein a extending in parallel along the longitudinal direction of the rectangular or stripe-shaped irregularities. In claim 1 or claim 2 ,
The semiconductor device according to claim 1, wherein a width of the concave bottom portion is wider than a width of the convex top portion in a direction perpendicular to the longitudinal direction . In any one of Claims 1 thru | or 3 ,
The semiconductor device according to claim 1, wherein the width of the concave bottom portion is three times or more the width of the convex upper portion in a direction perpendicular to the longitudinal direction. An insulating film having a plurality of rectangular or striped irregularities;
Wherein the insulating film, and a thin film transistor using a crystalline semiconductor film having a plurality of channel formation region provided on between the plural respective edges near the center and the plurality of convex top of each convex top,
A semiconductor device comprising:
The plurality of channel formation regions are separated from each other, and are positioned between the source and drain regions of the crystalline semiconductor film provided over each of the plurality of convex upper portions,
Each of the plurality of switch Yaneru forming region, wherein a extending along the longitudinal direction of the rectangular or stripe-shaped irregularities. An insulating film having a plurality of rectangular or striped irregularities;
Wherein the insulating film, and a thin film transistor using a crystalline semiconductor film having a plurality of channel formation region provided on between the plural respective edges near the center and the plurality of convex top of each convex top,
A semiconductor device comprising:
The plurality of channel formation regions are separated from each other, and are positioned between the source and drain regions of the crystalline semiconductor film provided over each of the plurality of convex upper portions,
Each of the plurality of switch Yaneru forming region, wherein a extending in parallel along the longitudinal direction of the rectangular or stripe-shaped irregularities. In claim 5 or claim 6 ,
The semiconductor device according to claim 1, wherein a width of the convex upper portion is wider than a width of the concave bottom portion in a direction perpendicular to the longitudinal direction . In any one of Claim 5 thru | or 7 ,
The semiconductor device according to claim 1, wherein the width of the convex top is three times or more the width of the concave bottom in a direction perpendicular to the longitudinal direction. In any one of Claims 1 thru | or 8 ,
Insulating film having the irregularities, a first insulating film made of silicon oxide or silicon oxynitride is provided on the first insulating film, the second consisting of silicon nitride or oxynitride of silicon having a rectangular or striped pattern wherein a having an insulating film. In any one of Claims 1 thru | or 9 ,
The convex portion of the insulating film has a trapezoidal cross-sectional shape in a direction perpendicular to the longitudinal direction. In any one of Claims 1 to 10 ,
The semiconductor device is characterized in that the concentration of oxygen in the channel formation region is 2 × 10 ¹⁹ atoms / cm ³ or less. In any one of Claims 1 to 11 ,
The semiconductor device, wherein the concentration of carbon in the channel formation region is 5 × 10 ¹⁸ atoms / cm ³ or less. In any one of Claims 1 to 12 ,
The semiconductor device according to claim 1, wherein the concentration of nitrogen in the channel formation region is 1 × 10 ¹⁹ atoms / cm ³ or less. A laser oscillation device;
An optical system for laser light oscillated from the laser oscillator is condensed to be linear,
First means for moving the irradiation position of the focused laser beam;
A second means for storing input pattern information;
A third means for forming an insulating film having striped or rectangular irregularities on the substrate according to the pattern information stored in the second means;
A fourth means for forming a semiconductor film on the insulating film;
And fifth means for reading the pattern information of the semi-conductor film,
Sixth means for storing the read pattern information;
And the second storage pattern information means, said sixth means to the stored pattern information of the reference to the position information of the substrate obtained from the thickness of the semi-conductor film, the second From the pattern information stored in the means or the pattern information stored in the sixth means, the scanning path of the laser beam is determined so as to include the concave bottom portion of the semiconductor film, and the first means is controlled. A seventh means for increasing the crystallinity of the semiconductor film by moving the laser beam according to the scanning path;
By patterning the semiconductor film having the crystallinity is enhanced, and the eighth means for forming an island over between near the center and the concave bottom portion of the edge of the concave bottom portions,
A semiconductor device production system comprising: A laser oscillation device;
An optical system for laser light oscillated from the laser oscillator is condensed to be linear,
First means for moving the irradiation position of the focused laser beam;
A second means for storing input pattern information;
A third means for forming an insulating film having striped or rectangular irregularities on the substrate according to the pattern information stored in the second means;
A fourth means for forming a semiconductor film on the insulating film;
And fifth means for reading the pattern information of the semi-conductor film,
Sixth means for storing the read pattern information;
And the second storage pattern information means, said sixth means to the stored pattern information of the reference to the position information of the substrate obtained from the thickness of the semi-conductor film, the second From the pattern information stored in the means or the pattern information stored in the sixth means, a scanning path of the laser beam is determined so as to include the convex upper portion of the semiconductor film, and the first means is controlled. A seventh means for increasing the crystallinity of the semiconductor film by moving the laser light according to the scanning path;
Patterning the semiconductor film having improved crystallinity to form an island between the vicinity of the center of the convex upper portion and the edge of the convex upper portion;
A semiconductor device production system comprising: In claim 14 or claim 15 ,
A semiconductor device production system, wherein the fifth means uses a charge coupled device. In any one of claims 14 to 16,
A semiconductor device production system, wherein the laser beam scanning is performed in a reduced pressure atmosphere or an inert gas atmosphere. In any one of Claim 14 thru / or Claim 17 ,
The laser beam may be one or more selected from YAG laser, YVO ₄ laser, YLF laser, YAlO ₃ laser, glass laser, ruby laser, alexandride laser, Ti: sapphire laser or Nd: YVO ₄ laser. A semiconductor device production system characterized by being output. In any one of Claim 14 thru / or Claim 17 ,
The production system of a semiconductor device, wherein the laser beam is output using a slab laser. In any one of claims 14 to 19 ,
A semiconductor device production system, wherein the laser beam is a continuously oscillated laser beam . In any one of claims 14 to 20 ,
Production system for a semiconductor device, wherein the laser beam is a laser beam of a second harmonic of the fundamental wave.

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