JP3908129B2 - Method for manufacturing semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser processing apparatus and a laser irradiation method for crystallizing a semiconductor substrate or a semiconductor film using a laser beam or activating after ion implantation, a semiconductor device formed using the laser apparatus, and a manufacturing method thereof. The present invention relates to a method and an electronic apparatus using the semiconductor device.
[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 polysilicon film has a higher field effect mobility (also referred to as mobility) than a TFT using a conventional amorphous silicon 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. Since a glass substrate is inferior in heat resistance and easily deforms by heat, when a polysilicon TFT is formed on the glass substrate, laser annealing is used for crystallization of the semiconductor film in order to avoid 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 or an amorphous layer formed on a semiconductor substrate or semiconductor film, or a technique for crystallizing an amorphous semiconductor film formed on a substrate. pointing. 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. It is known to be crystallized by heating for a very short time.
[0006]
[Problems to be solved by the invention]
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 beam spot is several cm ² As described above, mass productivity can be improved. In particular, when the shape of the beam spot 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]
Recently, however, 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. When the crystal grain size in the semiconductor film increases, the mobility of the TFT formed using the semiconductor film increases, and variations in TFT characteristics due to crystal grain boundaries are suppressed. For this reason, continuous wave lasers are starting to attract attention.
[0008]
However, in general, a continuous wave laser has a smaller maximum output energy than a pulsed laser, and therefore the beam spot size is 10. ^-3 mm ² About small. Therefore, in order to process a single large substrate, it is necessary to move the beam irradiation position on the substrate vertically and horizontally.
[0009]
In order to move the beam irradiation position vertically and horizontally, a method of changing the irradiation direction of the beam by fixing the position of the substrate, a method of moving the position of the substrate by fixing the irradiation direction of the beam, and the above two There are methods that combine methods.
[0010]
When the irradiation direction of the beam is changed, the irradiation angle of the beam with respect to the substrate changes depending on the irradiation position. When the irradiation angle changes, the intensity of the beam reflected by the substrate and the intensity of the interference change depending on the position of the substrate, so that the processing on the substrate cannot be performed uniformly. For example, when a semiconductor film is crystallized by laser irradiation, a difference in crystallinity occurs depending on the position of the substrate.
[0011]
On the other hand, when moving the position of the substrate while fixing the beam irradiation direction, the beam irradiation angle with respect to the substrate is fixed regardless of the position of the substrate. It becomes simple (for example, refer patent document 1).
[0012]
[Patent Document 1]
JP 05-275336 A (page 3-4)
[0013]
However, a problem in moving the substrate is a time loss accompanying the change of direction.
[0014]
In FIG. 20, the direction of movement of the irradiation position of the beam on the substrate when the position of the substrate is moved while the irradiation direction of the beam is fixed is indicated by an arrow. In general, laser irradiation is performed by moving the irradiation position in a certain direction, changing the direction, and moving the irradiation position in the certain direction again. At this time, if the moving speed of the irradiation position changes depending on the position of the substrate, it becomes difficult to uniformly process the substrate. Therefore, it is important to keep the movement speed of the irradiation position constant. In order to change the movement direction of the irradiation position, as shown in the part surrounded by the broken line in FIG. 20, when the irradiation position deviates from the substrate. It is common to do it. After the irradiation position deviates from the substrate, stop the movement of the substrate, change the direction of movement of the substrate, increase the moving speed of the substrate to a certain value again, and then irradiate the substrate with laser light It is necessary to. Therefore, a predetermined time is inevitably required to change the direction of the substrate, which causes a reduction in the processing speed of the substrate.
[0015]
This is a problem that occurs even when the beam irradiation direction is changed, and it takes a predetermined time to change the beam irradiation direction, which causes a reduction in the processing speed of the substrate.
[0016]
In particular, in the case of a continuous wave laser, unlike a pulsed laser, the size of a beam spot is originally small, so that the processing efficiency is low, and improving the processing speed of the substrate is an important issue.
[0017]
In view of the above-described problems, an object of the present invention is to provide a continuous-wave laser device and a method for manufacturing a semiconductor device using the laser device, which can increase the processing efficiency as compared with the related art.
[0018]
[Means for Solving the Problems]
The laser apparatus according to the present invention includes a first means for installing an object to be processed, a second means for rotating the object to be processed installed on the first means, and a first means for moving the center of rotation on a straight line. And a fourth means capable of irradiating laser light from a certain position and a certain direction to a certain region within the range in which the workpiece is moved.
[0019]
Then, a certain region where the laser beam is irradiated exists on an extension of the straight line along which the center of rotation moves.
[0020]
While rotating the object to be processed by the second means, the center of the rotation is moved on a straight line by the third means, so that a certain region where the laser beam is irradiated overlaps with the object to be processed. The entire object to be processed can be irradiated with laser light.
[0021]
Furthermore, in order to make the irradiation time of the laser light constant depending on the part to be processed, the rotation speed is adjusted with the movement of the center of rotation. Specifically, the rotation speed is decreased as the certain area irradiated with the laser beam is further away from the center of rotation, and the rotation speed is increased as the distance from the center of rotation is approached.
[0022]
In the laser apparatus of the present invention, even if the laser beam is irradiated from a certain position and a certain direction, the second means and the third means do not change the moving direction of the object to be processed by the second means and the third means. The irradiation position of the laser beam can be moved in the X direction and the Y direction, and the entire surface of the object to be processed can be irradiated with the laser beam. Therefore, there is no time loss associated with the change of the moving direction of the object to be processed, and the processing efficiency can be increased as compared with the conventional case.
[0023]
Further, since the irradiation angle of the laser beam irradiated by the fourth means is fixed regardless of the irradiation position, the intensity of the beam reflected and returning from the object to be processed is strong. It is possible to prevent the thickness and the like from being different depending on the irradiation position, and to process the object to be processed almost uniformly. For example, when a semiconductor film is crystallized by laser irradiation, it is possible to prevent a difference in crystallinity depending on the position of the semiconductor film. In addition, the optical system can be simplified as compared with the case where the entire object to be processed is irradiated with laser light by changing the beam irradiation direction.
[0024]
Note that a plurality of first means may be provided, and a plurality of objects to be processed may be processed in parallel. However, the centers of rotation of all the workpieces are matched. With the above configuration, the processing efficiency can be further increased.
[0025]
The laser device of the present invention is based on a continuous wave laser, but of course, a pulsed laser may be used.
[0026]
The application of the laser apparatus of the present invention is not limited to crystallization of a semiconductor film. The laser apparatus of the present invention can be used for all of the laser annealing methods described above.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the structure of the laser apparatus of this invention is demonstrated. FIG. 1A shows a side view of the light-emitting device of the present invention, and FIG. 1B shows a top view.
[0028]
The laser apparatus of the present invention shown in FIG. 1 has a plurality of stages 101 corresponding to a first means for installing an object to be processed. Here, an example in which four stages are provided will be described. By providing a plurality of stages and processing a plurality of objects to be processed in parallel, the processing efficiency can be further increased. On each stage 101, an object 100 to be irradiated with laser light is installed.
[0029]
Each stage 101 is installed on a turntable 103, and the turntable 103 is moved in the direction of an arrow about a workpiece 104 by a motor for the turntable 103 (hereinafter referred to as a turntable motor) 106. Can be rotated. The direction of rotation can be set as appropriate by the designer. The turntable 103 and the turntable motor 106 correspond to the second means of the laser apparatus of the present invention. However, the second means included in the laser apparatus of the present invention is not limited to this configuration, and any means that can rotate the workpiece 100 placed on the stage 101 may be used.
[0030]
Note that the centers of rotation of all the workpieces 100 coincide.
[0031]
The turntable 103 is movable along the guide rail 102. The guide rail is installed so that the center of rotation of the turntable 103 moves on a straight line when the turntable 103 is moved along the guide rail 102.
[0032]
The means for moving the turntable 103 along the guide rail 102 corresponds to the third means included in the laser apparatus of the present invention. Specifically, in FIG. 1, a moving motor (hereinafter referred to as a moving motor) 105 for the turntable 103 and a guide rail 102 correspond to the third means. However, the third means in the laser apparatus of the present invention is not limited to the configuration shown in FIG. 1 as long as the center of rotation of the workpiece can be moved on a straight line.
[0033]
The laser oscillator and the other optical system 107 can irradiate a specific region within a range in which the workpiece 100 moves from a certain position and a certain direction. The oscillation device and the other optical system 107 correspond to the fourth means of the laser device of the present invention.
[0034]
The laser can be appropriately changed depending on the purpose of processing. A known laser can be used as the fourth means of the laser apparatus of the present invention. As the laser, a continuous wave or pulsed gas laser or solid laser can be used. There are excimer laser, Ar laser, Kr laser, etc. as gas laser, and YAG laser, YVO as solid laser. ₄ Laser, YLF laser, YAlO ₃ Laser, glass laser, ruby laser, alexandry G Laser, Ti: sapphire laser, Y ₂ O ₃ A laser etc. are mentioned. Solid lasers include YAG, YVO doped with Cr, Nd, Er, Ho, Ce, Co, Ti, Yb or Tm. ₄ , YLF, YAlO ₃ 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.
[0035]
Furthermore, after converting infrared laser light emitted from a solid-state laser into green laser light using a nonlinear optical element, ultraviolet laser light obtained by another nonlinear optical element can also be used.
[0036]
The laser apparatus of the present invention may include means for adjusting the temperature of the object to be processed in addition to the above four means.
[0037]
FIG. 2 simply shows the movement of the turntable of FIG. The turntable 103 rotates in the direction indicated by the arrow 110 around 104. Then, the rotation center 104 moves in the direction indicated by the arrow 111. On the extension of the linear trajectory along which the center 104 of the turntable 103 moves, there is a certain region 109 irradiated with laser light.
[0038]
Next, how laser light is actually irradiated onto the workpiece 100 will be described. FIG. 3 shows a state in which laser light is irradiated on the workpiece 100 by the laser apparatus shown in FIG.
[0039]
FIG. 3A and FIG. 3B show a change in position of the turntable 103 over time when the workpiece 100 is irradiated with laser light. From FIG. 3A to FIG. 3B, the stage 101 rotates in the direction of arrow 110 around 104, and the center of rotation 104 of the turntable 103 moves in the direction of arrow 111.
[0040]
A certain region 109 to which the laser beam is irradiated exists on an extension of a linear locus along which the center 104 of the turntable 103 moves.
[0041]
As the turntable 103 rotates, a certain region 109 irradiated with laser light is irradiated onto the turntable 103 so as to draw a locus 108 as indicated by a broken line. The laser beam locus 108 draws a circle centering on 104. The workpiece 100 is irradiated with laser light at a portion overlapping the locus of the laser light.
[0042]
When the center 104 of the turntable 103 moves in the direction of the arrow 111 and the distance between the center 104 and the fixed region 109 irradiated with the laser beam is increased, the radius of the circle drawn by the fixed region 109 irradiated with the laser beam Will grow. On the contrary, when the distance between the center 104 and the certain region 109 irradiated with the laser light is reduced, the radius of the circle drawn by the certain region 109 irradiated with the laser light becomes smaller. Therefore, when the portion of the object to be processed 100 and the laser beam locus 108 shifts with time, the entire surface of the object to be processed 100 can be finally irradiated with laser light.
[0043]
Note that since the laser beam is irradiated even on a portion of the turntable 103 that does not overlap the workpiece 100, the turntable 103 is preferably formed of a material that is not deformed or damaged by the laser light.
[0044]
In FIG. 4, the moving direction of the irradiation position of the laser beam in the workpiece 100 irradiated with the laser beam in FIG. 3 is indicated by an arrow. The number of arrows is the same as the number of rotations of the turntable 103, and the number of arrows increases as the number of rotations increases.
[0045]
In order to make the irradiation time of the laser light constant depending on the portion of the object to be processed, the rotation speed is adjusted as the rotation center moves. In addition, it is important to determine the rotation speed of the object to be processed 100 and the moving speed of the center of rotation in consideration of an appropriate irradiation time of the laser beam in each part of the object to be processed 100. Specifically, the rotation speed is decreased as the certain area irradiated with the laser beam is further away from the center of rotation, and the rotation speed is increased as the distance from the center of rotation is approached. For example, when used for crystallization of a semiconductor film, the energy density is 5 × 10 5. ^Four ~ 1.3 × 10 ^Five (Cm ² / W), the moving speed of the irradiation position should be kept at 10 to 100 cm / sec, preferably 20 to 50 cm / sec.
[0046]
Further, if it is intended to irradiate the entire surface of the workpiece 100 with laser light, it is necessary to appropriately adjust the rotational speed of the workpiece 100 and the moving speed of the center 104 of rotation. If the moving speed of the center of rotation 104 is too high relative to the rotational speed of the workpiece 100, the entire surface of the workpiece cannot be irradiated with laser light.
[0047]
Further, by adjusting the rotation speed of the object to be processed 100 and the moving speed of the center of rotation, it is possible to irradiate each part of the object to be processed 100 with the laser light a plurality of times. In addition, after moving the center of rotation in one direction, the object to be processed 100 can be irradiated with laser light a plurality of times by moving in the opposite direction.
[0048]
With the above configuration, the laser apparatus of the present invention moves the irradiation position of the laser beam on the object to be processed without changing the moving direction of the object to be processed even when the laser beam is irradiated from a certain position and a certain direction. The entire surface of the object to be processed can be irradiated with laser light. Therefore, there is no time loss associated with the change of the moving direction of the object to be processed, and the processing efficiency can be increased as compared with the conventional case.
[0049]
In addition, since the irradiation angle of the laser beam to the object to be processed is fixed regardless of the irradiation position, the intensity of the beam reflected by the object to be processed and the intensity of interference are prevented from changing depending on the irradiation position. Thus, it is possible to perform the processing on the object to be processed substantially uniformly. For example, when the semiconductor film is crystallized by laser irradiation, it is possible to prevent a difference in crystallinity depending on the position of the object to be processed. In addition, the optical system can be simplified as compared with the case where the entire object to be processed is irradiated with laser light by changing the beam irradiation direction.
[0050]
【Example】
Examples of the present invention will be described below.
[0051]
Example 1
In this embodiment, a case will be described in which laser light is irradiated so that the edge portions of the laser light do not overlap each time when laser irradiation is performed a plurality of times.
[0052]
In general, the energy of the edge of the laser beam is different from that of the other portions, and there are cases where the processing of the object to be processed cannot be performed uniformly. Therefore, by avoiding overlapping of the laser light edge in multiple laser irradiations, the non-uniformity of energy at the edge can be alleviated and the processing of the workpiece can be performed almost uniformly. become able to.
[0053]
In order not to overlap the edges, the center of rotation of the object to be processed is shifted within a range of a distance smaller than the width of the locus of the laser beam in the first laser irradiation and the second laser irradiation, There is a method of shifting the moving range of the workpiece. However, the center of rotation in the second and subsequent laser irradiations is present on an extension of a line connecting the center of rotation in the first laser irradiation and a certain position where the laser light is irradiated.
[0054]
FIG. 5A shows a cross-sectional view of the laser device at the start of the first laser irradiation, and FIG. 5B shows a cross-sectional view of the laser device at the start of the second laser irradiation. Reference numeral 301 denotes a turntable, 303 a stage, and 304 a workpiece.
[0055]
In each of the first laser irradiation and the second laser irradiation, the center of the turntable 303 is shifted by the width t. The width t is made smaller than the width of the laser beam trajectory. Since the position of the object to be processed is shifted by the width t at the time when the laser irradiation is started between the first laser irradiation and the second laser irradiation, the object to be processed accompanying the movement of the center of rotation The moving range of the object 304 is also different.
[0056]
By the above method, the edge of the laser beam in the first laser irradiation and the edge of the laser beam in the second laser irradiation do not overlap, and the unevenness of energy at the edge portion is alleviated, Processing can be performed almost uniformly.
[0057]
(Example 2)
In this embodiment, a method different from that in Embodiment 1 will be described in which laser light is irradiated so that the edge portions of the laser light do not overlap each other when laser irradiation is performed a plurality of times.
[0058]
In this embodiment, in order not to overlap the edges, the irradiation position of the laser beam on the turntable is changed in the first laser irradiation and the second laser irradiation. FIG. 6 shows the locus of laser light in the first laser irradiation and the second laser irradiation on the rotary table. Reference numeral 401 denotes a turntable, and 402 denotes an object to be processed.
[0059]
Reference numeral 403 denotes a laser beam trajectory in the first laser irradiation, and reference numeral 404 denotes a laser light trajectory in the second laser irradiation. The laser beam trajectory 403 and the laser beam trajectory 404 overlap each other, and their edges do not overlap each other. In the first laser irradiation, processing is performed in a portion overlapping the laser beam trajectory 403 of the workpiece 402, and in the second laser irradiation, processing is performed in a portion overlapping the laser beam trajectory 404 of the workpiece 402. Made.
[0060]
By the above method, since the edge of the laser beam in the first laser irradiation and the edge of the laser beam in the second laser irradiation do not overlap, the unevenness of energy at the edge portion is alleviated and the object is processed. Processing can be performed almost uniformly.
[0061]
This embodiment can be implemented in combination with the first embodiment.
[0062]
(Example 3)
In this embodiment, a structure for irradiating laser light from the front surface and the back surface of a film to be processed formed on the object to be processed will be described.
[0063]
FIG. 7A shows a side view of the laser device of this embodiment. In the laser device of the present invention illustrated in FIG. 7A, a reflector 420 for reflecting laser light is disposed between an object to be processed 410 and a stage 411.
[0064]
The stage 411 is installed on a turntable 413, and the turntable 413 is rotated by a turntable motor 416. Further, the turntable 413 is movable along the guide rail 402 by a moving motor 415. In addition, when the turntable 413 is moved along the guide rail 402, the guide rail 402 is installed so that the center of rotation of the turntable 413 moves on a straight line.
[0065]
The processing object 410 can be irradiated with laser light from a certain position and a certain direction by the oscillation device and the other optical systems 417 and 418. A certain region irradiated with the laser light exists on an extension of a linear locus along which the center of rotation of the turntable 413 moves.
[0066]
In this embodiment, a part of the laser beam is reflected on the surface of the substrate and the so-called return light that returns the same optical path as the incident light has adverse effects such as fluctuations in the output of the laser oscillation device, frequency, etc. In order to prevent the laser beam from being exerted, the laser beam is not incident perpendicularly to the substrate, but is incident obliquely with respect to the substrate. In this case, since the laser light is light with high directivity and energy density, it is preferable to install a damper to absorb the reflected light in order to prevent the reflected light from irradiating an inappropriate place. Note that cooling water circulates in the damper to prevent the temperature of the damper from rising due to absorption of reflected light.
[0067]
Note that an isolator may be installed in order to remove the return light and stabilize the laser oscillation without causing the laser light to enter the substrate obliquely.
[0068]
FIG. 7B shows the positional relationship between the workpiece 410 and the reflector 420 in FIG.
[0069]
In FIG. 7B, an object to be processed 410 includes a light-transmitting substrate 421, an insulating film 422 formed on a surface thereof (a surface on which a thin film or an element is formed), an amorphous semiconductor film, and the like. 423 is formed. In addition, a reflector 420 for reflecting the laser light is disposed under the translucent substrate 421.
[0070]
As the light-transmitting substrate 421, a glass substrate, a quartz substrate, a crystallized glass substrate, or a plastic substrate is used. The insulating film 422 may be an insulating film containing silicon such as a silicon oxide film or a silicon nitride oxide film (SiOxNy). The amorphous semiconductor film 410 can be an amorphous silicon film, an amorphous silicon germanium film, or the like.
[0071]
Further, the reflector 420 may be a substrate on which a metal film is formed on the surface (laser light reflecting surface) or a substrate made of a metal element. In this case, any material may be used for the metal film. Typically, a metal film containing any element of aluminum, silver, tungsten, titanium, and tantalum is used.
[0072]
Further, instead of disposing the reflector 420, it is also possible to directly form the metal film as described above on the back surface (surface opposite to the front surface) of the translucent substrate 421 and reflect the laser beam there. However, the configuration is based on the premise that the metal film formed on the back surface in the manufacturing process of the semiconductor device is not removed.
[0073]
Then, the amorphous semiconductor film 410 is irradiated with a laser beam processed into a linear shape via an optical system 418 (only a cylindrical lens is shown in the drawing). At this time, the laser light applied to the amorphous semiconductor film 410 is irradiated with the laser light that is directly irradiated through the optical system 418 and the reflector 420 once reflected by the reflector 420. It is important that the optical system 418 is designed so that a laser beam can be obtained. Note that in this specification, laser light applied to the surface of the amorphous semiconductor film is referred to as primary laser light, and laser light applied to the back surface is referred to as secondary laser light.
[0074]
The laser beam that has passed through the optical system 418 has an incident angle of 45 to 90 ° with respect to the substrate surface in the process of being condensed. Therefore, the secondary laser light irradiates around the back side of the amorphous semiconductor film 410. In addition, by providing an undulating portion on the reflecting surface of the reflector 420 to diffusely reflect the laser light, the secondary laser light can be obtained more efficiently.
[0075]
In particular, the wavelength of the second harmonic of the YAG laser is 532 nm, and when the amorphous semiconductor film is irradiated, it is within the wavelength range (around 530 nm) that is not reflected by the amorphous semiconductor film. Further, in this wavelength range, since the laser beam that passes through the amorphous semiconductor film has a sufficient amount of light, it can be efficiently irradiated by irradiating the amorphous semiconductor film from the back side again using a reflector. . The laser energy of the second harmonic is as large as about 1.5 J / pulse at the maximum value (in the existing YAG laser apparatus), and when processed into a linear shape, the length in the longitudinal direction should be dramatically increased. This enables large area laser light irradiation.
[0076]
FIG. 7C illustrates the positional relationship between the workpiece 410 and the reflector 420 as viewed from the arrow 425 in FIG. In this embodiment, the incident angle with respect to the substrate 421 is kept larger than 0 and smaller than 90 ° in order to prevent the return light from following the original optical path and returning to the oscillation device 417. More specifically, it is kept at 5 to 30 °.
[0077]
When a plane that is a plane perpendicular to the irradiation surface and includes a short side when the long beam shape is regarded as a rectangle is defined as an incident surface, the incident angle θ of the laser beam is defined as It is desirable that θ ≧ arctan (W / 2d) is satisfied when the length is W, the thickness of the substrate that is placed on the irradiation surface and is transparent to the laser beam is d. When the locus of the laser beam is not on the incident surface, the incident angle of the locus projected onto the incident surface is defined as θ. If the laser beam 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 beam 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.
[0078]
As described above, according to this embodiment, it is possible to split the laser light into the primary laser light and the secondary laser light and irradiate the front and back surfaces of the amorphous semiconductor film.
[0079]
This embodiment can be implemented in combination with Embodiment 1 or Embodiment 2.
[0080]
Example 4
In this embodiment, the step of crystallizing a semiconductor film by laser annealing using the laser device of the present invention is applied to a method for manufacturing an active matrix semiconductor display device having a driver circuit on the same substrate as the pixel portion. Will be described.
[0081]
FIG. 8A is a top view of a liquid crystal panel in which a pixel portion 201, a signal line driver circuit 202, and a scan line driver circuit 203 are provided over a substrate 200. FIG. In FIG. 8A, the irradiation position of the laser light moves in the direction of the arrow indicated by the broken line.
[0082]
When a semiconductor film is irradiated with a laser beam by the laser apparatus of the present invention, the locus of the laser beam does not draw a complete straight line but draws a gentle arc. Therefore, when the semiconductor film is crystallized using the laser apparatus of the present invention, the laser beam irradiation trace is formed in an arc shape in the semiconductor film. Strictly speaking, this arc has a different radius of curvature for each arc, and the radius of curvature decreases when the irradiation position and the center of rotation are close, and increases when the arc is far. However, since the size of the active layer of the TFT formed by patterning the semiconductor film is smaller than the radius of the arc, even if the irradiation trace of each laser beam of the active layer remains, the irradiation The trace is almost straight.
[0083]
8B is an enlarged view of a part 204 of the pixel portion 201 in FIG. 8A, FIG. 8C is an enlarged view of a part 205 of the signal line driver circuit 202, and FIG. An enlarged view of part 206 is shown in FIG.
[0084]
In each of the pixel portion 201, the signal line driver circuit 202, and the scanning line driver circuit 203, a plurality of island-shaped semiconductor films serving as active layers of the TFTs are formed. Reference numerals 207, 208, and 209 are portions that become active layers of TFTs after patterning. A broken line 220 is an irradiation trace of the laser beam.
[0085]
The laser beam irradiation trace 220 is substantially along the direction in which the channel moves or vice versa.
[0086]
This embodiment can be implemented in combination with the first to third embodiments.
[0087]
(Example 5)
In this embodiment, an example will be described in which a semiconductor film formed on an insulating surface by a known film formation method is patterned into an island shape and then crystallized by laser annealing using the laser apparatus of the present invention.
[0088]
FIG. 9A illustrates a state where the island-shaped semiconductor film 450 is crystallized by being irradiated with laser light. The island-shaped semiconductor film 450 has an amorphous structure and is not limited to a semiconductor material, but is preferably formed of silicon, a silicon germanium (SiGe) alloy, or the like.
[0089]
A broken line 451 indicates the position of the active layer of the TFT obtained by patterning the island-shaped semiconductor film 450 after crystallization by laser annealing. The irradiation position 452 of the laser beam is moved along the direction in which the channel moves or the opposite direction.
[0090]
FIG. 9B shows an enlarged view of a portion 453 where the laser light is first irradiated in the island-shaped semiconductor film 450. In this embodiment, laser light irradiation is intentionally started from the edge portion of the island-shaped semiconductor film. An edge refers to a portion having a corner of a semiconductor film when the island-shaped semiconductor film is viewed from a direction in which laser light is irradiated.
[0091]
In FIG. 9B, the angle θ1 of the edge when viewed from the direction in which the laser beam is irradiated is set to be less than 180 °. Also against the insulating surface
The angle θ2 of the side surface of the island-shaped semiconductor film 450 is 90 ± 10 °, and more preferably 90 ± 5 °.
[0092]
When laser light irradiation is started from an edge portion of the island-shaped semiconductor film 450, a crystal having an orientation of (100) plane starts to grow from the edge portion. When the irradiation of the laser light onto the island-shaped semiconductor film 450 is completed, the orientation rate of the (100) plane of the entire island-shaped semiconductor film 450 can be increased.
[0093]
When the orientation ratio of the (100) plane of the semiconductor film is increased, the mobility of the TFT can be increased when used as an active layer. In addition, when the orientation ratio of the (100) plane of the semiconductor film is high, variations in the film quality of the gate insulating film formed thereon can be reduced, and hence variations in the threshold voltage of the TFT can be reduced. it can.
[0094]
In addition, when a laser beam is irradiated to a board | substrate with the laser apparatus of this invention, the locus | trajectory of a laser beam draws a gentle arc instead of drawing a perfect straight line. However, since the size of the island-shaped semiconductor film is small compared to the radius of the arc, even if the irradiation trace of the laser light of each island-shaped semiconductor film remains, the irradiation trace is almost linear. It has become.
[0095]
Next, an example in which the above-described method for crystallizing a semiconductor film is applied to a method for manufacturing an active matrix semiconductor display device having a driver circuit over the same substrate as a pixel portion will be described.
[0096]
FIG. 23A is a top view of a liquid crystal panel in which a pixel portion 501, a signal line driver circuit 502, and a scan line driver circuit 503 are provided over a substrate 500. In FIG. 23A, the irradiation position of the laser light moves in the direction of the arrow indicated by the broken line.
[0097]
FIG. 23B is an enlarged view of a part 504 of the pixel portion 501 in FIG. 23A, FIG. 23C is an enlarged view of a part 505 of the signal line driver circuit 502, and FIG. An enlarged view of part 506 is shown in FIG.
[0098]
In each of the pixel portion 501, the signal line driver circuit 502, and the scanning line driver circuit 503, a plurality of island-shaped semiconductor films serving as active layers of the TFTs are formed. Laser light is applied to the areas indicated by 507, 508, and 509, and each area moves in the direction of the arrow.
[0099]
Each of the island-like semiconductor films is arranged so that laser light irradiation is started from the edge portion.
[0100]
Note that the size and shape of the island-shaped semiconductor film are determined in accordance with the shape of the TFT formed in each of the pixel portion 501, the signal line driver circuit 502, and the scan line driver circuit 503. Further, an active layer of a plurality of TFTs may be formed from one island-shaped semiconductor film.
[0101]
This embodiment can be implemented in combination with the first to fourth embodiments.
[0102]
(Example 6)
In this embodiment, a laser beam oscillation device and other optical systems used in the laser device of the present invention will be described.
[0103]
FIG. 10 shows the structure of the laser device of this example. Reference numeral 520 denotes a laser beam oscillation device capable of continuous oscillation or pulse oscillation. The oscillation device 520 keeps its temperature constant by the chiller 527. The chiller 527 is not necessarily provided, but by keeping the temperature of the oscillation device 520 constant, the energy of the laser light output from the oscillation device can be prevented from varying depending on the temperature of the oscillation device.
[0104]
The laser light output from the oscillation device 520 is changed in its optical path by fixed mirrors 521, 522, and 523, collected by lenses 524 and 525 such as a collimator lens or a cylindrical lens, and is processed on a stage 528. The object 526 is irradiated. Needless to say, the number of optical systems is not limited, and it is only necessary to include means for irradiating the workpiece with a laser beam from a certain position and a certain angle.
[0105]
Note that the laser beam irradiated to the object to be processed may be reflected on the surface and incident on the optical system again, thereby damaging the laser oscillation device. It is desirable to make it incident.
[0106]
Then, as described in the embodiment, the irradiation position of the laser beam on the workpiece 526 is moved by rotating the stage 528 on the turntable 529 and moving the center of rotation linearly, The entire surface of the workpiece 526 can be processed.
[0107]
This embodiment can be implemented in combination with the first to fifth embodiments.
[0108]
(Example 7)
In this embodiment, a laser beam oscillation device and other optical systems used in the laser device of the present invention will be described.
[0109]
FIG. 11 shows the structure of the laser device of this example. The laser device of this embodiment uses a plurality of oscillation devices, and combines a plurality of laser beams oscillated from the plurality of oscillation devices into one. In this embodiment, a case where three oscillation devices 550 (550a, 550b, 550c) are used will be described as an example.
[0110]
The oscillation of the laser beam from each oscillation device can be freely controlled by the control device 552. At least one of the three oscillation devices 550 converts the laser beam to be output into the second harmonic, the third harmonic, and the fourth harmonic by a nonlinear optical element. In this embodiment, the wavelengths of the laser beams output from all the oscillation devices 550 are converted by the nonlinear optical elements 551a, 551b, and 551c, respectively. The wavelengths to be converted may be the same or any of them may be different.
[0111]
The laser beams output from the three oscillation devices 550 are combined into one. Specifically, in this embodiment, each laser beam is incident on the waveguide 554 via the fiber array 553 corresponding to each laser beam, and is combined into one laser beam. A thin film polarizing element (TFP: Thin Film Polarizer) or other polarizers can also be used.
[0112]
The laser beam synthesized through the waveguide 554 is again incident on the optical fiber 555 to reduce the diffusion of the laser beam. The laser light emitted from the optical fiber 555 is condensed by the convex lens 556 and reaches the object 559 installed on the stage 540.
[0113]
The laser beam synthesized into one has an energy density corresponding to the laser beam oscillated from the high-power laser. Laser light oscillated from the same laser has high coherence, but laser light oscillated from different lasers do not interfere with each other. Therefore, laser beams combined into a plurality of lasers complement each other and interfere with each other. It is possible to reduce. In addition, nonlinear optical elements used to convert laser light into higher harmonics are required to have sufficient heat resistance and durability because the laser light is transmitted through them. Is big. Therefore, if the energy of the transmitted laser beam is as small as possible, the lifetime of the nonlinear optical element is extended, leading to cost reduction. The configuration of the present embodiment, in which the wavelengths of a plurality of laser beams are converted by a plurality of nonlinear optical elements and then combined into one laser beam, the wavelength of one laser beam is converted by a single nonlinear optical element. However, the burden on one nonlinear optical element is reduced. Therefore, the lifetime of each nonlinear optical element can be extended and the cost can be reduced.
[0114]
Such laser light can be irradiated onto the entire surface of the object to be processed using an optical system such as an optical fiber, a galvanometer, or a polygon meter.
[0115]
The shape of the laser beam on the irradiated surface varies depending on the type of laser, and can 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.
[0116]
Furthermore, when laser light is incident perpendicular to the substrate of the object to be processed, a part of the laser light is reflected on the surface of the substrate and returns to the same optical path as the incident light, so-called return light, The return light has adverse effects such as fluctuations in laser output and frequency, and rod destruction. For this reason, it is preferable to install an isolator in order to remove the return light and stabilize the oscillation of the laser.
[0117]
On the other hand, in order to prevent the return light, the laser beam can be incident obliquely with respect to the substrate. However, since the laser light is light having high directivity and energy density, it is preferable to install a damper to absorb the reflected light in order to prevent the reflected light from irradiating an inappropriate place. Note that cooling water circulates in the damper to prevent the temperature of the damper from rising due to absorption of reflected light.
[0118]
Then, as described in the embodiment, by rotating the stage 540 on the turntable 541 and moving the center of the rotation on a straight line, the irradiation position of the laser beam on the workpiece 559 is moved, The entire surface of the object to be processed 559 can be processed.
[0119]
This embodiment can be implemented in combination with the first to fifth embodiments.
[0120]
(Example 8)
In this embodiment, a laser beam oscillation device and other optical systems used in the laser device of the present invention will be described.
[0121]
FIG. 12 shows the structure of the laser device of this example. In the laser device of this embodiment, the laser light oscillated from the oscillation device 571 is converted into a harmonic by the nonlinear optical element 572, and is divided into a plurality of laser beams by the mirror 573, which is a dividing means.
[0122]
Each laser beam is reflected by mirrors 574a and 574b, which are laser beam forming means having a periodic energy distribution, and is collected by cylindrical lenses 575a and 575b, respectively, on a stage (not shown in this embodiment). It reaches the workpiece 561 that has been installed. In the object to be processed 561, a plurality of laser beams are combined to cause interference, and a laser beam having a periodic energy distribution is formed. The cylindrical lenses 575a and 575b are not necessarily installed, but the energy density can be increased on the irradiation surface by installing them.
[0123]
The shape of the laser light emitted from the laser differs depending on the type of laser, and is circular if the rod shape is cylindrical, and rectangular if it is slab type.
[0124]
Then, as described in the embodiment, by rotating the stage on the turntable 560 and moving the center of the rotation on a straight line, the irradiation position of the laser light on the object to be processed 561 is moved, and the object to be processed is moved. The entire surface of the processing object 561 can be processed.
[0125]
This embodiment can be implemented in combination with the first to fifth embodiments.
[0126]
Example 9
In this embodiment, a method for manufacturing an active matrix substrate 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.
[0127]
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.
[0128]
Next, a base film 601 formed of an insulating film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film is formed over the substrate 600 by a known means (a sputtering method, an LPCVD method, a plasma CVD method, or the like). Although a two-layer structure is used as the base film 601 in this embodiment, a single-layer film of the insulating film or a structure in which two or more layers are stacked may be used.
[0129]
Next, semiconductor layers 602 to 606 are formed over the base film. The semiconductor layers 602 to 606 are formed by forming a semiconductor film with a thickness of 25 to 80 nm (preferably 30 to 60 nm) by a known means (sputtering method, LPCVD method, plasma CVD method, etc.), and crystallized by a laser crystallization method. Let The laser crystallization method can be performed using the laser apparatus of the present invention. 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. Then, the obtained crystalline semiconductor film is patterned into a desired shape to form semiconductor layers 602 to 606. Examples of the semiconductor film include an amorphous semiconductor film, a microcrystalline semiconductor film, a crystalline semiconductor film, and the like, and a compound semiconductor film having an amorphous structure such as an amorphous silicon germanium film may be applied.
[0130]
Laser oscillators are pulse oscillation type or continuous emission type excimer laser, YAG laser, YVO _Four Use a laser. Crystallization conditions are appropriately selected by the practitioner. When an excimer laser is used, the pulse oscillation frequency is 300 Hz and the laser energy density is 100 to 400 mJ / cm. ² (Typically 200-300mJ / cm ² ). When a YAG laser is used, the second harmonic is used and the pulse oscillation frequency is set to 30 to 300 kHz, and the laser energy density is set to 300 to 600 mJ / cm. ² (Typically 350-500mJ / cm ² ) Then, laser light condensed linearly with a width of 100 to 1000 μm, for example 400 μm, is irradiated over the entire surface of the substrate, and the superposition rate (overlap rate) of the linear laser light at this time is 50 to 90%.
[0131]
As the laser, a continuous wave or pulsed gas laser or solid laser can be used. There are excimer laser, Ar laser, Kr laser, etc. as gas laser, and YAG laser, YVO as solid laser. ₄ Laser, YLF laser, YAlO ₃ Laser, glass laser, ruby laser, alexandry G Laser, Ti: sapphire laser, Y ₂ O ₃ A laser etc. are mentioned. Solid lasers include YAG, YVO doped with Cr, Nd, Er, Ho, Ce, Co, Ti, Yb or Tm. ₄ , YLF, YAlO ₃ Lasers using crystals such as 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.
[0132]
In crystallization of the amorphous semiconductor film, in order to obtain a crystal with a large grain size, it is preferable to use a solid-state laser capable of continuous oscillation and apply the second to fourth harmonics of the fundamental wave. Typically, Nd: YVO _Four It is desirable to apply the second harmonic (532 nm) or the third harmonic (355 nm) of the laser (fundamental wave 1064 nm). Specifically, continuous output YVO with an output of 10 W _Four Laser light emitted from the laser is converted into a harmonic by a non-linear optical element. 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.
[0133]
Subsequently, semiconductor layers 602 to 606 are formed by a patterning process using a photolithography method.
[0134]
Further, after forming the semiconductor layers 602 to 606, a small amount of impurity element (boron or phosphorus) may be doped in order to control the threshold value of the TFT.
[0135]
Next, a gate insulating film 607 covering the semiconductor layers 602 to 606 is formed. The gate insulating film 607 is formed of an insulating film containing silicon with a thickness of 40 to 150 nm by a plasma CVD method or a sputtering method. In this embodiment, a silicon oxynitride film (composition ratio: Si = 32%, O = 59%, N = 7%, H = 2%) with a thickness of 110 nm is formed by plasma CVD. Needless to say, the gate insulating film is not limited to the silicon oxynitride film, and another insulating film containing silicon may be used as a single layer or a stacked structure.
[0136]
When a silicon oxide film is used, TEOS (Tetraethyl Orthosilicate) and O 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. The silicon oxide film thus manufactured can obtain good characteristics as a gate insulating film by thermal annealing at 400 to 500 ° C. thereafter.
[0137]
Next, a first conductive film 608 with a thickness of 20 to 100 nm and a second conductive film 609 with a thickness of 100 to 400 nm are stacked over the gate insulating film 607. In this example, a first conductive film 608 made of a TaN film with a thickness of 30 nm and a second conductive film 609 made of a W film with a thickness of 370 nm were stacked. The TaN film is formed by sputtering, and is sputtered in a nitrogen-containing atmosphere using a Ta target. The W film was formed by sputtering using a W target. In addition, tungsten hexafluoride (WF ₆ It can also be formed by a thermal CVD method using In any case, in order to use as a gate electrode, it is necessary to reduce the resistance, and the resistivity of the W film is desirably 20 μΩcm or less. The resistivity of the W film can be reduced by increasing the crystal grains. However, when there are many impurity elements such as oxygen in the W film, the crystallization is hindered and the resistance is increased. Therefore, in this embodiment, a sputtering method using a target of high purity W (purity 99.9999%) is used, and the W film is formed with sufficient consideration so that impurities are not mixed in from the gas phase during film formation. By forming, a resistivity of 9 to 20 μΩcm can be realized.
[0138]
In this embodiment, the first conductive film 608 is TaN and the second conductive film 609 is W. However, there is no particular limitation, and all of them are Ta, W, Ti, Mo, Al, Cu, Cr, Nd. You may form with the element selected from these, or the alloy material or compound material which has the said element as a main component. Alternatively, a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus may be used. Further, an AgPdCu alloy may be used. In addition, the first conductive film is formed using a tantalum (Ta) film, the second conductive film is formed using a W film, the first conductive film is formed using a titanium nitride (TiN) film, and the second conductive film is formed. The first conductive film is formed of tantalum nitride (TaN), the second conductive film is formed of W, the first conductive film is formed of tantalum nitride (TaN) film, and the first conductive film is formed of tantalum nitride (TaN) film. Alternatively, the second conductive film may be a combination of Al films, the first conductive film may be a tantalum nitride (TaN) film, and the second conductive film may be a Cu film.
[0139]
The structure is not limited to the two-layer structure, and for example, a three-layer structure in which a tungsten film, an aluminum-silicon alloy (Al-Si) film, and a titanium nitride film are sequentially stacked may be employed. In the case of a three-layer structure, tungsten nitride may be used instead of tungsten, or an aluminum / titanium alloy film (Al—Ti) is used instead of an aluminum / silicon alloy film (Al—Si) film. Alternatively, a titanium film may be used instead of the titanium nitride film.
[0140]
Note that it is important to select an optimum etching method and etchant type depending on the material of the conductive film.
[0141]
Next, resist masks 610 to 615 are formed by photolithography, and a first etching process for forming electrodes and wirings is performed. The first etching process is performed under the first and second etching conditions. (FIG. 13 (B)) In this embodiment, ICP (Inductively Coupled Plasma) etching method is used as the first etching condition, and CF is used as an etching gas. _Four And Cl ₂ And O ₂ The gas flow ratio is 25:25:10 (sccm), and 500 W of RF (13.56 MHz) power is applied to the coil-type electrode at a pressure of 1 Pa to generate plasma and perform etching. 150 W RF (13.56 MHz) power is also applied to the substrate side (sample stage), and a substantially negative self-bias voltage is applied. The W film is etched under this first etching condition so that the end portion of the first conductive layer is tapered.
[0142]
Thereafter, the resist masks 610 to 615 are not removed, but the second etching condition is changed, and the etching gas is changed to CF. _Four And Cl ₂ The gas flow ratio is 30:30 (sccm), and 500 W of RF (13.56 MHz) power is applied to the coil-type electrode at a pressure of 1 Pa to generate plasma and etching for about 30 seconds. Went. 20 W of RF (13.56 MHz) power is also applied to the substrate side (sample stage), and a substantially negative self-bias voltage is applied. CF _Four And Cl ₂ Under the second etching condition in which is mixed, the W film and the TaN film are etched to the same extent. Note that in order to perform etching without leaving a residue on the gate insulating film, it is preferable to increase the etching time at a rate of about 10 to 20%.
[0143]
In the first etching process, the shape of the mask made of resist is made suitable, and the end portions of the first conductive layer and the second conductive layer are tapered due to the effect of the bias voltage applied to the substrate side. It becomes. The angle of this taper portion is 15 to 45 °. Thus, the first shape conductive layers 617 to 622 (the first conductive layers 617 a to 622 a and the second conductive layers 617 b to 622 b) composed of the first conductive layer and the second conductive layer by the first etching treatment. Form. Reference numeral 616 denotes a gate insulating film, and a region which is not covered with the first shape conductive layers 617 to 622 is etched by about 20 to 50 nm to form a thinned region.
[0144]
Next, a second etching process is performed without removing the resist mask. Here, CF is used as an etching gas. _Four And Cl ₂ And O ₂ Then, the W film is selectively etched. At this time, second conductive layers 628b to 633b are formed by a second etching process. On the other hand, the first conductive layers 617a to 622a are hardly etched, and the second shape conductive layers 628 to 633 are formed.
[0145]
Then, a first doping process is performed without removing the resist mask, and an impurity element imparting n-type conductivity is added to the semiconductor layer at a low concentration. The doping process may be performed by ion doping or ion implantation. The condition of the ion doping method is a dose of 1 × 10 ¹³ ~ 5x10 ¹⁴ /cm ² The acceleration voltage is 40 to 80 kV. In this embodiment, the dose is 1.5 × 10 ¹³ /cm ² The acceleration voltage is 60 kV. As an impurity element imparting n-type, an element belonging to Group 15, typically phosphorus (P) or arsenic (As), is used here, but phosphorus (P) is used. In this case, the conductive layers 628 to 633 serve as a mask for the impurity element imparting n-type, and the impurity regions 623 to 627 are formed in a self-aligning manner. Impurity regions 623 to 627 have 1 × 10 ¹⁸ ~ 1x10 ²⁰ atoms / cm ^Three An impurity element imparting n-type is added in a concentration range of.
[0146]
After removing the resist mask, new resist masks 634a to 634c are formed, and the second doping process is performed at an acceleration voltage higher than that of the first doping process. The condition of the ion doping method is a dose of 1 × 10 ¹³ ~ 1x10 ¹⁵ /cm ² The acceleration voltage is set to 60 to 120 kV. In the doping treatment, the second conductive layers 628b to 632b are used as a mask for the impurity element, and doping is performed so that the impurity element is added to the semiconductor layer below the tapered portion of the first conductive layer. Subsequently, the third doping process is performed by lowering the acceleration voltage than the second doping process to obtain the state of FIG. The condition of the ion doping method is a dose of 1 × 10 ¹⁵ ~ 1x10 ¹⁷ /cm ² And an acceleration voltage of 50 to 100 kV. The low-concentration impurity regions 636, 642, and 648 overlapping with the first conductive layer by the second doping process and the third doping process have 1 × 10 ¹⁸ ~ 5x10 ¹⁹ atoms / cm ^Three An impurity element imparting n-type is added in a concentration range of 1 × 10 in the high concentration impurity regions 635, 641, 644 and 647. ¹⁹ ~ 5x10 ^{twenty one} atoms / cm ^Three An impurity element imparting n-type is added in a concentration range of.
[0147]
Needless to say, by setting the acceleration voltage to be appropriate, the second and third doping processes can be performed in a single doping process to form the low-concentration impurity region and the high-concentration impurity region.
[0148]
Next, after removing the resist mask, new resist masks 650a to 650c are formed, and a fourth doping process is performed. By this fourth doping treatment, impurity regions 653, 654, 659, and 660 in which an impurity element imparting a conductivity type opposite to the one conductivity type is added to the semiconductor layer that becomes the active layer of the p-channel TFT are formed. To do. The second conductive layers 628a to 632a are used as masks for the impurity element, and an impurity element imparting p-type is added to form an impurity region in a self-aligning manner. In this embodiment, the impurity regions 653, 654, 659, and 660 are diborane (B ₂ H ₆ ) Using an ion doping method. (FIG. 14B) In the fourth doping process, the semiconductor layer forming the n-channel TFT is covered with masks 650a to 650c made of resist. By the first to third doping treatments, phosphorus is added to the impurity regions 653, 659 and 654, 660 at different concentrations, and the concentration of the impurity element imparting p-type is set to 1 × in any of the regions. 10 ¹⁹ ~ 5x10 ^{twenty one} atoms / cm ^Three By performing the doping treatment so as to become, no problem arises because it functions as the source region and drain region of the p-channel TFT.
[0149]
Through the above steps, impurity regions are formed in the respective semiconductor layers.
[0150]
Next, the resist masks 650a to 650c are removed, and a first interlayer insulating film 661 is formed. The first interlayer insulating film 661 is formed of an insulating film containing silicon with a thickness of 100 to 200 nm by using a plasma CVD method or a sputtering method. In this embodiment, a silicon oxynitride film having a thickness of 150 nm is formed by a plasma CVD method. Needless to say, the first interlayer insulating film 661 is not limited to the silicon oxynitride film, and another insulating film containing silicon may be used as a single layer or a stacked structure.
[0151]
Next, as shown in FIG. 14C, a laser irradiation method is used as the activation treatment. When the laser annealing method is used, it is possible to use a laser used for crystallization. In the case of activation, the moving speed is the same as that of crystallization, and 0.01-100 MW / cm. ² Degree (preferably 0.01 to 10 MW / cm ² ) Energy density is required. Further, a continuous wave laser may be used for crystallization, and a pulsed laser may be used for activation.
[0152]
In addition, an activation process may be performed before forming the first interlayer insulating film.
[0153]
Then, hydrogenation can be performed by heat treatment (heat treatment at 300 to 550 ° C. for 1 to 12 hours). This step is a step of terminating dangling bonds in the semiconductor layer with hydrogen contained in the first interlayer insulating film 661. The semiconductor layer can be hydrogenated regardless of the presence of the first interlayer insulating film. As other means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) or heat treatment at 300 to 650 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% hydrogen good.
[0154]
Next, a second interlayer insulating film 662 made of an inorganic insulating film material or an organic insulating material is formed over the first interlayer insulating film 661. In this embodiment, an acrylic resin film having a thickness of 1.6 μm is formed, but a film having a viscosity of 10 to 1000 cp, preferably 40 to 200 cp, and having a surface with unevenness is used.
[0155]
In this embodiment, in order to prevent specular reflection, the surface of the pixel electrode is formed with the unevenness by forming the second interlayer insulating film having the unevenness on the surface. In addition, a convex portion may be formed in a region below the pixel electrode in order to make the surface of the pixel electrode uneven to achieve light scattering. In that case, since the convex portion can be formed using the same photomask as that of the TFT, it can be formed without increasing the number of steps. In addition, this convex part should just be suitably provided on the board | substrate of pixel part area | regions other than wiring and a TFT part. Thus, irregularities are formed on the surface of the pixel electrode along the irregularities formed on the surface of the insulating film covering the convex portions.
[0156]
Alternatively, a film whose surface is planarized may be used as the second interlayer insulating film 662. In that case, after forming the pixel electrode, adding a step such as a known sandblasting method or etching method to make the surface uneven, prevent specular reflection, and increase the whiteness by scattering the reflected light Is preferred.
[0157]
In the driver circuit 686, wirings 663 to 667 that are electrically connected to the impurity regions are formed. Note that these wirings are formed by patterning a laminated film of a Ti film having a thickness of 50 nm and an alloy film (alloy film of Al and Ti) having a thickness of 500 nm. Of course, not only a two-layer structure but also a single-layer structure or a laminated structure of three or more layers may be used. Further, the wiring material is not limited to Al and Ti. For example, a wiring may be formed by patterning a laminated film in which Al or Cu is formed on a TaN film and a Ti film is further formed. (Fig. 15)
[0158]
In the pixel portion 687, a pixel electrode 670, a gate wiring 669, and a connection electrode 668 are formed. With this connection electrode 668, the source wiring (stack of 633a and 633b) is electrically connected to the pixel TFT. The gate wiring 669 is electrically connected to the gate electrode of the pixel TFT. In addition, the pixel electrode 670 is electrically connected to the drain region 642 of the pixel TFT, and is further electrically connected to the semiconductor layer 659 functioning as one electrode forming the storage capacitor. Further, as the pixel electrode 670, it is desirable to use a material having excellent reflectivity such as a film containing Al or Ag as a main component or a laminated film thereof.
[0159]
As described above, a CMOS circuit including an n-channel TFT 681 and a p-channel TFT 682, a driver circuit 686 having an n-channel TFT 683, a pixel portion 687 having a pixel TFT 684 and a storage capacitor 685 are formed over the same substrate. can do. Thus, the active matrix substrate is completed.
[0160]
An n-channel TFT 681 in the driver circuit 686 has a channel formation region 637, a low concentration impurity region 636 (GOLD region) overlapping with the first conductive layer 628a which forms part of the gate electrode, and a high concentration functioning as a source region or a drain region. An impurity region 652 and an impurity region 690 into which an impurity element imparting n-type conductivity is introduced are provided. The p-channel TFT 682, which is connected to the n-channel TFT 681 by the electrode 666 to form a CMOS circuit, includes a channel formation region 640, a high-concentration impurity region 654 that functions as a source region or a drain region, and an impurity element that imparts n-type conductivity And an impurity region 653 into which an impurity element imparting p-type conductivity is introduced. In the n-channel TFT 683, a channel formation region 643, a low-concentration impurity region 642 (GOLD region) that overlaps with the first conductive layer 630a that forms part of the gate electrode, and a high-concentration impurity that functions as a source region or a drain region A region 656 and an impurity region 691 into which an impurity element imparting n-type conductivity is introduced are provided.
[0161]
A pixel TFT 684 in the pixel portion is provided with a channel formation region 646, a low concentration impurity region 645 (LDD region) formed outside the gate electrode, a high concentration impurity region 658 functioning as a source region or a drain region, and an n-type. An impurity region 692 into which an impurity element is introduced is provided. In addition, an impurity element imparting n-type conductivity and an impurity element imparting p-type conductivity are added to the semiconductor layer functioning as one electrode of the storage capacitor 685. The storage capacitor 685 is formed of an electrode (stack of 632a and 632b) and a semiconductor layer using the insulating film 616 as a dielectric.
[0162]
In the pixel structure of this embodiment, the end portions of the pixel electrodes are arranged and formed so as to overlap the source wiring so that the gap between the pixel electrodes is shielded from light without using a black matrix.
[0163]
This embodiment can be implemented in combination with the first to eighth embodiments.
[0164]
(Example 10)
In this example, a process of manufacturing a reflective liquid crystal display device from the active matrix substrate manufactured in Example 9 will be described below. FIG. 16 is used for the description.
[0165]
First, after obtaining the active matrix substrate in the state of FIG. 15 according to Embodiment 9, an alignment film 867 is formed on at least the pixel electrode 670 on the active matrix substrate of FIG. In this embodiment, before the alignment film 867 is formed, a columnar spacer 872 for maintaining the distance between the substrates is formed by patterning an organic resin film such as an acrylic resin film. Further, instead of the columnar spacers, spherical spacers may be scattered over the entire surface of the substrate.
[0166]
Next, a counter substrate 869 is prepared. Next, colored layers 870 and 871 and a planarization film 873 are formed over the counter substrate 869. The red colored layer 870 and the blue colored layer 871 are overlapped to form a light shielding portion. Further, the light shielding portion may be formed by partially overlapping the red colored layer and the green colored layer.
[0167]
In this example, the substrate shown in Example 9 is used. Accordingly, at least the gap between the gate wiring 669 and the pixel electrode 670, the gap between the gate wiring 669 and the connection electrode 668, and the gap between the connection electrode 668 and the pixel electrode 670 need to be shielded from light. In this example, the respective colored layers were arranged so that the light-shielding portions formed by the lamination of the colored layers overlapped at the positions where light shielding should be performed, and the counter substrate was bonded.
[0168]
As described above, the number of steps can be reduced by shielding the gap between the pixels with the light shielding portion formed by the lamination of the colored layers without forming a light shielding layer such as a black mask.
[0169]
Next, a counter electrode 876 made of a transparent conductive film was formed over the planarization film 873 at least in the pixel portion, an alignment film 874 was formed over the entire surface of the counter substrate, and a rubbing process was performed.
[0170]
Then, the active matrix substrate on which the pixel portion and the driver circuit are formed and the counter substrate are attached to each other with a sealant 868. A filler is mixed in the sealing material 868, and two substrates are bonded to each other with a uniform interval by the filler and the columnar spacer. Thereafter, a liquid crystal material 875 is injected between both substrates and completely sealed with a sealant (not shown). A known liquid crystal material may be used for the liquid crystal material 875. In this way, the reflection type liquid crystal display device shown in FIG. 16 is completed. If necessary, the active matrix substrate or the counter substrate is divided into a desired shape. Further, a polarizing plate (not shown) was attached only to the counter substrate. And FPC was affixed using the well-known technique.
[0171]
The liquid crystal display device manufactured as described above includes a TFT manufactured using a semiconductor film in which a laser beam having a periodic or uniform energy distribution is irradiated and crystal grains having a large particle size are formed. Therefore, the operation characteristics and reliability of the liquid crystal display device can be sufficient. And such a liquid crystal display device can be used as a display part of various electronic devices.
[0172]
Note that this embodiment can be implemented in combination with the first to ninth embodiments.
[0173]
(Example 11)
In this example, an example of manufacturing a light-emitting device using the manufacturing method of a TFT when manufacturing an active matrix substrate shown in Example 9 will be described below. In this specification, 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. It is. 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. In addition, luminescence in an organic compound includes light emission (fluorescence) when returning from a singlet excited state to a ground state and light emission (phosphorescence) when returning from a triplet excited state to a ground state, one of these, Or both luminescence is included.
[0174]
In the present specification, all layers formed between the anode and the cathode in the light emitting element are defined as organic light emitting layers. Specifically, the organic light emitting layer includes a light emitting layer, a hole injection layer, an electron injection layer, a hole transport layer, an electron transport layer, and the like. Basically, a light emitting element has a structure in which an anode layer, a light emitting layer, and a cathode layer are sequentially laminated. In addition to this structure, an anode layer, a hole injection layer, a light emitting layer, a cathode layer, and an anode layer , A hole injection layer, a light emitting layer, an electron transport layer, a cathode layer and the like may be laminated in this order.
[0175]
FIG. 17 is a cross-sectional view of the light emitting device of this example. In FIG. 17, the switching TFT 733 provided over the substrate 700 is formed by using the manufacturing method of Embodiment 9.
[0176]
Note that although a double gate structure in which two channel formation regions are formed is used in this embodiment, a single gate structure in which one channel formation region is formed or a triple gate structure in which three channel formation regions are formed may be used.
[0177]
A driver circuit provided over the substrate 700 is formed by using the manufacturing method of Embodiment 9. In this embodiment, a single gate structure is used, but a double gate structure or a triple gate structure may be used.
[0178]
Further, the wirings 701 and 703 function as source wirings of the CMOS circuit, and the wiring 702 functions as a drain wiring. The wiring 704 functions as a wiring that electrically connects the source wiring 708 and the source region of the switching TFT, and the wiring 705 functions as a wiring that electrically connects the drain wiring 709 and the drain region of the switching TFT.
[0179]
Note that the current control TFT 734 is formed by using the manufacturing method of Example 9. In this embodiment, a single gate structure is used, but a double gate structure or a triple gate structure may be used.
[0180]
A wiring 706 is a source wiring (corresponding to a current supply line) of the current control TFT, and 707 is an electrode that electrically connects the drain region of the current control TFT and the pixel electrode 711.
[0181]
Reference numeral 711 denotes a pixel electrode (anode of the light emitting element) made of a transparent conductive film. As the transparent conductive film, a compound of indium oxide and tin oxide, a compound of indium oxide and zinc oxide, zinc oxide, tin oxide, or indium oxide can be used. Moreover, you may use what added the gallium to the said transparent conductive film. The pixel electrode 711 is formed on the flat interlayer insulating film 710 before forming the wiring. In this embodiment, it is very important to flatten the step due to the TFT using the flattening film 710 made of resin. Since the light emitting layer formed later is very thin, the presence of a step may cause a light emission failure. Therefore, it is desirable to planarize the pixel electrode before forming it so that the light emitting layer can be formed as flat as possible.
[0182]
After the wirings 701 to 707 are formed, a bank 712 is formed as shown in FIG. The bank 712 may be formed by patterning an insulating film or organic resin film containing silicon of 100 to 400 nm.
[0183]
Note that since the bank 712 is an insulating film, attention must be paid to electrostatic breakdown of elements during film formation. In this embodiment, carbon particles or metal particles are added to the insulating film that is the material of the bank 712 to reduce the resistivity and suppress the generation of static electricity. At this time, the resistivity is 1 × 10 ⁶ ~ 1x10 ¹² Ωm (preferably 1 × 10 ⁸ ~ 1x10 ^Ten The added amount of carbon particles and metal particles may be adjusted so that the resistance becomes Ωm).
[0184]
A light emitting layer 713 is formed on the pixel electrode 711. Although only one pixel is shown in FIG. 17, in this embodiment, light emitting layers corresponding to the respective colors R (red), G (green), and B (blue) are separately formed. In this embodiment, a low molecular weight organic light emitting material is formed by a vapor deposition method. Specifically, a copper phthalocyanine (CuPc) film having a thickness of 20 nm is provided as a hole injection layer, and a tris-8-quinolinolato aluminum complex (Alq) having a thickness of 70 nm is formed thereon as a light emitting layer. _Three ) A laminated structure provided with a film. Alq _Three The emission color can be controlled by adding a fluorescent dye such as quinacridone, perylene, or DCM1.
[0185]
However, the above example is an example of an organic light emitting material that can be used as a light emitting layer, and it is not absolutely necessary to limit to this. A light emitting layer (a layer for emitting light and moving carriers therefor) may be formed by freely combining a light emitting layer, a charge transport layer, or a charge injection layer. For example, in this embodiment, an example in which a low molecular weight organic light emitting material is used as the light emitting layer is shown, but a medium molecular weight organic light emitting material or a high molecular weight organic light emitting material may be used. Note that in this specification, an organic light-emitting material that does not have sublimation and has 20 or less molecules or a chain molecule length of 10 μm or less is referred to as a medium molecular organic light-emitting material. As an example of using a polymer organic light emitting material, a 20 nm polythiophene (PEDOT) film is provided by a spin coating method as a hole injection layer, and a paraphenylene vinylene (PPV) film of about 100 nm is provided thereon as a light emitting layer. Alternatively, a laminated structure may be used. If a PPV π-conjugated polymer is used, the emission wavelength can be selected from red to blue. It is also possible to use an inorganic material such as silicon carbide for the charge transport layer or the charge injection layer. Known materials can be used for these organic light emitting materials and inorganic materials.
[0186]
Next, a cathode 714 made of a conductive film is provided on the light emitting layer 713. In this embodiment, an alloy film of aluminum and lithium is used as the conductive film. Of course, a known MgAg film (magnesium and silver alloy film) may be used. As the cathode material, a conductive film made of an element belonging to Group 1 or Group 2 of the periodic table or a conductive film added with these elements may be used.
[0187]
When the cathode 714 is formed, the light emitting element 715 is completed. Note that the light-emitting element 715 here refers to a diode formed of a pixel electrode (anode) 711, a light-emitting layer 713, and a cathode 714.
[0188]
It is effective to provide a passivation film 716 so as to completely cover the light emitting element 715. As the passivation film 716, an insulating film including a carbon film, a silicon nitride film, or a silicon nitride oxide film is used, and the insulating film is used as a single layer or a combination thereof.
[0189]
At this time, it is preferable to use a film with good coverage as the passivation film, and it is effective to use a carbon film, particularly a DLC (diamond-like carbon) film. Since the DLC film can be formed in a temperature range from room temperature to 100 ° C., it can be easily formed over the light-emitting layer 713 having low heat resistance. In addition, the DLC film has a high blocking effect against oxygen and can suppress oxidation of the light-emitting layer 713. Therefore, the problem that the light emitting layer 713 is oxidized during the subsequent sealing process can be prevented.
[0190]
Further, a sealing material 717 is provided over the passivation film 716 and a cover material 718 is attached thereto. As the sealing material 717, an ultraviolet curable resin may be used, and it is effective to provide a substance having a hygroscopic effect or a substance having an antioxidant effect inside. In this embodiment, the cover material 718 is formed by forming a carbon film (preferably a diamond-like carbon film) on both surfaces of a glass substrate, a quartz substrate, or a plastic substrate (including a plastic film).
[0191]
Thus, a light emitting device having a structure as shown in FIG. 17 is completed. Note that it is effective to continuously process the steps from the formation of the bank 712 to the formation of the passivation film 716 using a multi-chamber type (or in-line type) film formation apparatus without releasing to the atmosphere. . Further, it is possible to continuously process the process up to the step of bonding the cover material 718 without releasing to the atmosphere.
[0192]
Thus, n-channel TFTs 731 and 732, a switching TFT (n-channel TFT) 733 and a current control TFT (n-channel TFT) 734 are formed on the substrate 700.
[0193]
Furthermore, as described with reference to FIGS. 17A and 17B, an n-channel TFT which is resistant to deterioration due to the hot carrier effect can be formed by providing an impurity region overlapping with the gate electrode through an insulating film. Therefore, a highly reliable light emitting device can be realized.
[0194]
In addition, in this embodiment, only the configuration of the pixel portion and the drive circuit is shown. However, according to the manufacturing process of this embodiment, other logic circuits such as a signal dividing circuit, a D / A converter, an operational amplifier, and a γ correction circuit are provided. Can be formed on the same insulator, and a memory and a microprocessor can also be formed.
[0195]
The light-emitting device manufactured as described above has a TFT manufactured using a semiconductor film on which large-sized crystal grains are formed by irradiation with laser light having a periodic or uniform energy distribution. The operational characteristics and reliability of the light emitting device can be sufficient. And such a light-emitting device can be used as a display part of various electronic devices.
[0196]
In addition, a present Example can be implemented in combination with any one of Example 1- Example 9.
[0197]
(Example 12)
In this embodiment, a structure different from that of Embodiment 11 of a pixel of a light emitting device which is one of the semiconductor devices of the present invention will be described. FIG. 18 is a cross-sectional view of a pixel of the light emitting device of this example.
[0198]
751 is an n-channel TFT, and 752 is a p-channel TFT. The n-channel TFT 751 includes a semiconductor film 753, a first insulating film 770, first electrodes 754 and 755, a second insulating film 771, and second electrodes 756 and 757. The semiconductor film 753 includes a first-concentration one-conductivity type impurity region 758, a second-concentration one-conductivity type impurity region 759, and channel formation regions 760 and 761.
[0199]
The first electrodes 754 and 755 and the channel formation regions 760 and 761 overlap each other with the first insulating film 770 interposed therebetween. In addition, the second electrodes 756 and 757 and the channel formation regions 760 and 761 overlap with the second insulating film 771 interposed therebetween.
[0200]
The p-channel TFT 752 includes a semiconductor film 780, a first insulating film 770, a first electrode 781, a second insulating film 771, and a second electrode 782. The semiconductor film 780 includes a first conductivity type impurity region 783 having a third concentration and a channel formation region 784.
[0201]
The first electrode 781 and the channel formation region 784 overlap with each other with the first insulating film 770 interposed therebetween. The second electrode 782 and the channel formation overlap with each other with the second insulating film 771 interposed therebetween.
[0202]
The first electrode 781 and the second electrode 782 are electrically connected through a wiring 790.
[0203]
The laser apparatus of the present invention can be used in the steps of crystallizing, activating, or other laser annealing of the semiconductor films 753 and 780.
[0204]
In this embodiment, a constant voltage is applied to the first electrode of the TFT used as a switching element (n-channel TFT 751 in this embodiment). By applying a constant voltage to the first electrode, variation in threshold value can be suppressed as compared with the case where there is one electrode, and off-state current can be suppressed.
[0205]
In addition, a TFT (p-channel TFT 752 in this embodiment) that flows a larger current than a TFT used as a switching element electrically connects the first electrode and the second electrode. By applying the same voltage to the first electrode and the second electrode, the depletion layer spreads quickly in the same way as when the film thickness of the semiconductor film is substantially reduced, so that the subthreshold coefficient can be reduced. The on-current can be increased. Therefore, the driving voltage can be lowered by using the TFT having this structure in the driving circuit. In addition, since the on-current can be increased, the TFT size (especially the channel width) can be reduced. Therefore, the integration density can be improved.
[0206]
In addition, a present Example can be implemented in combination with any one of Example 1- Example 11.
[0207]
(Example 13)
In this embodiment, a structure different from those in Embodiments 11 and 12 of a pixel of a light-emitting device that is one of the semiconductor devices of the present invention will be described. FIG. 19 is a cross-sectional view of a pixel of the light emitting device of this example.
[0208]
In FIG. 19, reference numeral 911 denotes a substrate, and 912 denotes an insulating film to be a base (hereinafter referred to as a base film). As the substrate 911, a light-transmitting substrate, typically a glass substrate, a quartz substrate, a glass ceramic substrate, or a crystallized glass substrate can be used. However, it must withstand the maximum processing temperature during the fabrication process.
[0209]
Reference numeral 8201 denotes a switching TFT, and 8202 denotes a current control TFT, which are formed of an n-channel TFT and a p-channel TFT, respectively. When the light emitting direction of the organic light emitting layer is the lower surface of the substrate (the surface on which the TFT and the organic light emitting layer are not provided), the above configuration is preferable. However, the switching TFT and the current control TFT may be either an n-channel TFT or a p-channel TFT.
[0210]
The switching TFT 8201 includes a source region 913, a drain region 914, an LDD region 915a to 915d, an isolation region 916, and channel formation regions 917a and 917b, a gate insulating film 918, gate electrodes 919a and 919b, and a first interlayer. An insulating film 920, a source signal line 921, and a drain wiring 922 are included. Note that the gate insulating film 918 or the first interlayer insulating film 920 may be common to all TFTs on the substrate, or may be different depending on a circuit or an element.
[0211]
Further, the switching TFT 8201 shown in FIG. 19 has a so-called double gate structure in which the gate electrodes 917a and 917b are electrically connected. Needless to say, not only a double gate structure but also a so-called multi-gate structure (a structure including an active layer having two or more channel formation regions connected in series) such as a triple gate structure may be used.
[0212]
The multi-gate structure is extremely effective in reducing the off-current. If the off-current of the switching TFT is made sufficiently low, the minimum capacity required for the storage capacitor connected to the gate electrode of the current control TFT 8202 can be reduced. Can be suppressed. That is, since the area of the storage capacitor can be reduced, the multi-gate structure is also effective in increasing the effective light emitting area of the light emitting element.
[0213]
Further, in the switching TFT 8201, the LDD regions 915a to 915d are provided so as not to overlap with the gate electrodes 919a and 919b with the gate insulating film 918 interposed therebetween. Such a structure is very effective in reducing off current. The length (width) of the LDD regions 915a to 915d may be set to 0.5 to 3.5 μm, typically 2.0 to 2.5 μm. Note that in the case of a multi-gate structure including two or more gate electrodes, an isolation region 916 (a region to which the same impurity element is added at the same concentration as the source region or the drain region) provided between channel formation regions It is effective for reducing the off current.
[0214]
Next, the current control TFT 8202 includes an active layer including a source region 926, a drain region 927, and a channel formation region 965, a gate insulating film 918, a gate electrode 930, a first interlayer insulating film 920, a source signal line 931, and the like. A drain wiring 932 is formed. In this embodiment, the current control TFT 8202 is a p-channel TFT.
[0215]
The drain region 914 of the switching TFT 8201 is connected to the gate 930 of the current control TFT 8202. Although not shown, specifically, the gate electrode 930 of the current control TFT 8202 is electrically connected to the drain region 914 of the switching TFT 8201 via the drain wiring (also referred to as connection wiring) 922. Note that the gate electrode 930 has a single gate structure, but may have a multi-gate structure. The source signal line 931 of the current control TFT 8202 is connected to a power supply line (not shown).
[0216]
Although the above has described the structure of the TFT provided in the pixel, a driving circuit is also formed at this time. FIG. 19 shows a CMOS circuit as a basic unit for forming a driving circuit.
[0217]
In FIG. 19, a TFT having a structure that reduces hot carrier injection while reducing the operating speed as much as possible is used as the n-channel TFT 8204 of the CMOS circuit. Note that the driver circuit here refers to a source signal side driver circuit and a gate signal side driver circuit. Of course, other logic circuits (level shifter, A / D converter, signal dividing circuit, etc.) can be formed.
[0218]
An active layer of the n-channel TFT 8204 in the CMOS circuit includes a source region 935, a drain region 936, an LDD region 937, and a channel formation region 938, and the LDD region 937 overlaps with the gate electrode 939 with a gate insulating film 918 interposed therebetween.
[0219]
The reason why the LDD region 937 is formed only on the drain region 936 side is to prevent the operation speed from being lowered. In addition, the n-channel TFT 8204 does not need to worry about the off-current value so much, and it is better to focus on the operation speed than that. Therefore, it is desirable that the LDD region 937 is completely overlapped with the gate electrode to reduce the resistance component as much as possible. That is, it is better to eliminate the so-called offset.
[0220]
Further, the p-channel TFT 8205 of the CMOS circuit is hardly concerned with deterioration due to hot carrier injection, so that it is not particularly necessary to provide an LDD region. Therefore, the active layer includes a source region 940, a drain region 941, and a channel formation region 961, and a gate insulating film 918 and a gate electrode 943 are provided thereon. Needless to say, it is possible to provide an LDD region as in the case of the n-channel TFT 8204 and take measures against hot carriers.
[0221]
Note that 942, 938, 917a, 917b, and 929 are masks for forming channel formation regions 961 to 965.
[0222]
Each of the n-channel TFT 8204 and the p-channel TFT 8205 has source signal lines 944 and 945 on the source region with a first interlayer insulating film 920 interposed therebetween. Further, the drain regions of the n-channel TFT 8204 and the p-channel TFT 8205 are electrically connected to each other by the drain wiring 946.
[0223]
The laser apparatus of the present invention can be used in crystallization of the active layer, activation, or other processes using laser annealing.
[0224]
In addition, the structure of a present Example can be implemented combining freely with Examples 1-11.
[0225]
(Example 14)
In this embodiment, an example will be described in which impurities mixed in a melted semiconductor film when the semiconductor film is crystallized by laser light irradiation are removed. A typical manufacturing procedure will be briefly described below with reference to FIGS.
[0226]
In FIG. 21A, reference numeral 1100 denotes a substrate having an insulating surface, 1101 denotes a base insulating film, and 1102 denotes a semiconductor film having an amorphous structure.
[0227]
First, a base insulating film 1101 made of an insulating film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film is formed over the substrate 1100 as a blocking layer. Here, a two-layer structure (a 50-nm-thick silicon oxynitride film and a 100-nm-thick silicon oxynitride film) is used as the base insulating film 1101, but a single-layer film or a structure in which two or more layers are stacked may be used. However, when it is not necessary to provide a blocking layer, the base insulating film is not necessarily formed. (FIG. 21 (A))
[0228]
Next, the semiconductor film 1102 having an amorphous structure is crystallized by a known method over the base insulating film to form a semiconductor film 1104 having a crystalline structure. (Fig. 21 (B))
[0229]
In this embodiment, a semiconductor film having a crystal structure is obtained by subjecting a semiconductor film 1102 having an amorphous structure obtained by plasma CVD, reduced pressure thermal CVD, or sputtering to laser annealing using the laser apparatus of the present invention. Crystallize.
[0230]
Note that a continuous wave or pulsed gas laser or solid state laser can be used as the laser oscillation device. There are excimer laser, Ar laser, Kr laser, etc. as gas laser, and YAG laser, YVO as solid laser. ₄ Laser, YLF laser, YAlO ₃ Laser, glass laser, ruby laser, alexandry G Laser, Ti: sapphire laser, Y ₂ O ₃ A laser etc. are mentioned. Solid lasers include YAG, YVO doped with Cr, Nd, Er, Ho, Ce, Co, Ti, Yb or Tm. ₄ , YLF, YAlO ₃ Lasers using crystals such as 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. For the detailed conditions in laser light irradiation, the description in Example 9 can be referred to.
[0231]
Note that the oxygen concentration (SIMS analysis) in the semiconductor film 1104 having a crystal structure is 5 × 10 5. ¹⁸ atoms / cm ^Three It is desirable to form the following.
[0232]
Next, a barrier layer 1105 containing silicon as a main component is formed over the semiconductor film 1104 having a crystal structure. Note that the barrier layer 1105 may be an extremely thin layer, and may be a natural oxide film, or may be an oxide film that is oxidized by generating ozone by irradiation with ultraviolet rays in an atmosphere containing oxygen. The barrier layer 1105 may be an oxide film oxidized with a solution containing ozone used for surface treatment called hydro-cleaning performed for removing carbon, that is, organic substances. This barrier layer 1105 is mainly used as an etching stopper. Further, after forming the barrier layer 1105, channel doping may be performed, and then activated by irradiating with strong light.
[0233]
Next, a second semiconductor film 1106 is formed over the barrier layer 1105. (FIG. 21C) The second semiconductor film 1106 may be a semiconductor film having an amorphous structure or a semiconductor film having a crystal structure. The thickness of the second semiconductor film 1106 is 5 to 50 nm, preferably 10 to 20 nm. The second semiconductor film 1106 contains oxygen (concentration of 5 × 10 5 in SIMS analysis). ¹⁸ atoms / cm ^Three Or more, preferably 1 × 10 ¹⁹ atoms / cm ^Three It is desirable to improve the gettering efficiency by containing the above.
[0234]
Next, a third semiconductor film (gettering site) 1107 containing a rare gas element is formed over the second semiconductor film 1106. The third semiconductor film 1107 may be a semiconductor film having an amorphous structure using a plasma CVD method, a low pressure thermal CVD method, or a sputtering method, or may be a semiconductor film having a crystal structure. The third semiconductor film may be a semiconductor film containing a rare gas element in the deposition step, or a rare gas element may be added after the formation of the semiconductor film not containing the rare gas element. In this embodiment, the third semiconductor film 1107 containing a rare gas element is formed in the deposition step, and then the third semiconductor film 1108 is formed by selectively adding a rare gas element. (FIG. 21D) Alternatively, the second semiconductor film and the third semiconductor film may be successively formed without exposure to the air. The sum of the thickness of the second semiconductor film and the thickness of the third semiconductor film may be 30 to 200 nm, for example, 50 nm.
[0235]
In this embodiment, the second semiconductor film 1106 forms a gap between the first semiconductor film 1104 and the third semiconductor film (gettering site) 1108. At the time of gettering, an impurity element such as a metal present in the semiconductor film 1104 tends to gather near the boundary of the gettering site. Therefore, the gettering site is obtained by the second semiconductor film 1106 as in this embodiment. It is desirable to improve the gettering efficiency by keeping the boundary of the first semiconductor film 1104 away from the first semiconductor film 1104. In addition, the second semiconductor film 1106 also has an effect of blocking the impurity element contained in the gettering site from diffusing and reaching the interface of the first semiconductor film during gettering. . Further, the second semiconductor film 1106 also has an effect of protecting the first semiconductor film from being damaged when a rare gas element is added.
[0236]
Next, gettering is performed. As a step of performing gettering, heat treatment may be performed in a nitrogen atmosphere at 450 to 800 ° C. for 1 to 24 hours, for example, at 550 ° C. for 14 hours. Moreover, you may irradiate strong light instead of heat processing. Moreover, you may irradiate strong light in addition to heat processing. Further, the substrate may be heated by injecting heated gas. In this case, heating may be performed at 600 ° C. to 800 ° C., more preferably at 650 ° C. to 750 ° C. for 1 to 60 minutes. Time can be shortened. By this gettering, the impurity element moves in the direction of the arrow in FIG. 21E, and the impurity element contained in the semiconductor film 1104 covered with the barrier layer 1105 is removed or the concentration of the impurity element is reduced. . Here, all the impurity elements are moved to the third semiconductor film 1108 so as not to be segregated in the first semiconductor film 1104, and the impurity elements contained in the first semiconductor film 1104 are hardly present, that is, the impurity element concentration in the film Is 1 × 10 ¹⁸ atoms / cm ^Three Below, desirably 1 × 10 ¹⁷ atoms / cm ^Three Getter enough to get:
[0237]
Next, after selectively removing only the semiconductor films 1106 and 1108 using the barrier layer 1105 as an etching stopper, a semiconductor layer 1109 having a desired shape is formed on the semiconductor film 1104 using a known patterning technique. (Fig. 21 (F))
[0238]
Next, after cleaning the surface of the semiconductor layer with an etchant containing hydrofluoric acid, an insulating film containing silicon as a main component and serving as the gate insulating film 1110 is formed. The surface cleaning and the formation of the gate insulating film are desirably performed continuously without exposure to the atmosphere.
[0239]
Next, after cleaning the surface of the gate insulating film, a gate electrode 1111 is formed, an impurity element imparting n-type conductivity (P, As, or the like), here phosphorus, is added as appropriate to the semiconductor, and the source region 1112 and the drain region 1113 are added. Form. After the addition, heat treatment, intense light irradiation, or laser light irradiation using the laser device of the present invention is performed to activate the impurity element. Simultaneously with activation, plasma damage to the gate insulating film and plasma damage to the interface between the gate insulating film and the semiconductor layer can be recovered. In particular, in an atmosphere of room temperature to 300 ° C., it is very effective to activate the impurity element by irradiating the second harmonic of the YAG laser from the front surface or the back surface. A YAG laser is a preferred activation means because it requires less maintenance.
[0240]
In the subsequent steps, an interlayer insulating film 1115 is formed, hydrogenation is performed, contact holes reaching the source region and the drain region are formed, a source electrode 1116 and a drain electrode 1117 are formed, and a TFT is completed. (Fig. 21 (G))
[0241]
The TFT thus obtained has at least the impurity element contained in the channel formation region 1114 removed and does not contain a rare gas element.
[0242]
Further, the present embodiment is not limited to the structure shown in FIG. 21, and a lightly doped drain (LDD) structure having an LDD region between a channel formation region and a drain region (or source region) if necessary. Also good. In this structure, a region to which an impurity element is added at a low concentration is provided between a channel formation region and a source region or a drain region formed by adding an impurity element at a high concentration, and this region is referred to as an LDD region. I'm calling. Furthermore, a so-called GOLD (Gate Overlapped LDD) structure in which an LDD region is disposed so as to overlap with a gate electrode through a gate insulating film may be employed.
[0243]
Although an n-channel TFT has been described here, a p-channel TFT can be formed by using an impurity element that imparts p-type to a semiconductor instead of an impurity element that imparts n-type to a semiconductor. Needless to say, you can.
[0244]
In this embodiment, the semiconductor film is patterned after the gettering is completed. However, this embodiment is not limited to this configuration. The patterning of the semiconductor film may be performed before crystallization, or may be performed after crystallization and before forming the barrier layer. Further, the semiconductor film is roughly patterned before crystallization or after crystallization and before forming the barrier layer, and after the gettering, patterning is performed again to form an active layer of the TFT. You may do it.
[0245]
Although the top gate TFT has been described as an example here, the present embodiment can be applied regardless of the TFT structure, for example, a bottom gate TFT (reverse stagger type) TFT or a forward stagger type TFT. It is possible.
[0246]
In addition, the structure of a present Example can be implemented combining freely with Examples 1-13.
[0247]
(Example 15)
In this embodiment, the laser device of the present invention has a second means for rotating the object to be processed, a third means for moving the center of rotation on a straight line, and the movement of the object to be processed. An example in which the operation of a fourth means for irradiating laser light to a certain region within a range from a certain position and a certain direction using a CPU will be described.
[0248]
The laser apparatus of the present invention shown in FIG. 22 has a stage 231 corresponding to a first means for installing an object 230 to be processed. A turntable 233 and a turntable motor 236 corresponding to second means capable of rotating the stage 231 are provided. Further, a guide rail 232 and a moving motor 235 corresponding to third means capable of moving the center of rotation on a straight line are provided. Further, a laser oscillation device and other optical system 237 corresponding to a fourth means capable of irradiating a specific region within a moving range of the workpiece 230 from a certain position and a certain direction are provided. Have.
[0249]
On the extension of the linear trajectory along which the center of rotation of the turntable 233 moves, there is a certain region where the laser beam is irradiated.
[0250]
In order to make the speed at which the irradiation position moves constant and to make the laser light irradiation time constant depending on the portion of the object to be processed, it is necessary to adjust the rotation speed as the rotation center moves. The CPU 240 controls the rotation speed of the object 230 and the moving speed of the center of rotation in consideration of the appropriate irradiation time of the laser beam in each part of the object 230. Specifically, the rotation speed is decreased as the certain area irradiated with the laser beam is further away from the center of rotation, and the rotation speed is increased as the distance from the center of rotation is approached.
[0251]
In addition, if the moving speed of the center of rotation 234 is too high relative to the rotational speed of the object to be processed 230, the entire surface of the object to be processed cannot be irradiated with laser light. For example, the rotational speed of the workpiece 230 and the moving speed of the center of rotation 234 are adjusted appropriately by the CPU.
[0252]
In addition, by adjusting the rotational speed of the object to be processed 230 and the moving speed of the center of rotation, each part of the object to be processed 230 can be irradiated with laser light a plurality of times. Further, after moving the center of rotation in one direction and then moving in the opposite direction, the object 230 can be irradiated with laser light a plurality of times.
[0253]
In addition, as shown in the second embodiment, when changing the irradiation position of the laser beam on the turntable in the first laser irradiation and the second laser irradiation, the CPU 240 controls the fourth means and sets the irradiation position. You may make it control.
[0254]
The laser apparatus of the present invention may include means for adjusting the temperature of the object to be processed in addition to the above four means. The means for adjusting the temperature of the object to be processed may be controlled by the CPU 240.
[0255]
This embodiment can be implemented in combination with Embodiments 1 to 14.
[0256]
(Example 16)
As electronic equipment using a semiconductor device formed by the laser device of the present invention, a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, a sound reproduction device (car audio, audio component, etc.), a notebook type Recording media such as personal computers, game machines, portable information terminals (mobile computers, mobile phones, portable game machines, electronic books, etc.), and image playback devices (specifically DVDs (digital versatile discs)) equipped with recording media And a device having a display capable of reproducing and displaying the image). Specific examples of these electronic devices are shown in FIGS.
[0257]
FIG. 24A 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. The semiconductor device of the present invention can be used for the display portion 2003. Since the semiconductor 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.
[0258]
FIG. 24B 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. The semiconductor device of the present invention can be used for the display portion 2102 and other circuits.
[0259]
FIG. 24C shows 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. The semiconductor device of the present invention can be used for the display portion 2203 and other circuits.
[0260]
FIG. 24D 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. The semiconductor device of the present invention can be used for the display portion 2302.
[0261]
FIG. 24E illustrates 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 A2403, a display portion B2404, and a recording medium (DVD or the like). A reading unit 2405, operation keys 2406, a speaker unit 2407, and the like are included. Although the display portion A 2403 mainly displays image information and the display portion B 2404 mainly displays character information, the semiconductor device of the present invention can be used for these display portions A, B 2403, 2404 and other circuits. Note that an image reproducing device provided with a recording medium includes a home game machine and the like.
[0262]
FIG. 24F illustrates a goggle type display (head mounted display), which includes a main body 2501, a display portion 2502, and an arm portion 2503. The semiconductor device of the present invention can be used for the display portion 2502 and other circuits.
[0263]
FIG. 24G 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. The semiconductor device of the present invention can be used for the display portion 2602 and other circuits.
[0264]
Here, FIG. 24H 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. The semiconductor device of the present invention can be used for the display portion 2703 and other circuits. Note that the display portion 2703 can reduce power consumption of the mobile phone by displaying white characters on a black background.
[0265]
In addition to the electronic devices described above, it can be used for a front-type or rear-type projector.
[0266]
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, the electronic device of this embodiment may use the semiconductor device having any structure shown in Embodiments 1 to 15.
[0267]
(Example 17)
In this embodiment, an example in which a semiconductor film is crystallized using the laser apparatus of the present invention will be described.
[0268]
In FIG. 25A, 3000 is a substrate having an insulating surface, 3001 is a base film which is an insulating film for preventing impurities in the substrate from entering the semiconductor film, and 3002 is a semiconductor film having an amorphous structure. .
[0269]
In FIG. 25A, a glass substrate, a quartz substrate, a ceramic substrate, or the like can be used as the substrate 3000. Alternatively, a silicon substrate, a metal substrate, or a stainless steel substrate with an insulating film formed thereon may be used. Alternatively, a plastic substrate having heat resistance that can withstand the processing temperature in this step may be used.
[0270]
First, as shown in FIG. 25A, a silicon oxide film, a silicon nitride film, or a silicon oxynitride film (SiO 2) is formed over a substrate 3000. _x N _y A base insulating film 3001 made of an insulating film such as) is formed. A typical example has a two-layer structure as the base insulating film 3001, and SiH _Four , NH _Three And N ₂ A first silicon oxynitride film formed using O as a reaction gas is formed to a thickness of 30 to 100 nm, SiH _Four And N ₂ A structure in which a second silicon oxynitride film formed using O as a reactive gas is formed to a thickness of 30 to 150 nm can be used. Alternatively, a three-layer structure in which a first silicon oxynitride film, a second silicon oxynitride film, and a silicon nitride film are sequentially stacked may be used.
[0271]
Next, a semiconductor film 3002 having an amorphous structure is formed over the base insulating film 3001. For the semiconductor film 3002, a semiconductor material containing silicon as its main component is used. Typically, an amorphous silicon film, an amorphous silicon germanium film, or the like is applied, and the film is formed to a thickness of 10 to 100 nm by a plasma CVD method, a low pressure CVD method, or a sputtering method. In order to obtain a semiconductor film having good crystallinity by subsequent crystallization, the concentration of impurities such as oxygen and nitrogen contained in the semiconductor film 3002 having an amorphous structure is set to 5 × 10. ¹⁸ atoms / cm ^Three It may be reduced to (atomic concentration measured by secondary ion mass spectrometry (SIMS)) or less. These impurities interfere with subsequent crystallization, and also increase the density of capture centers and recombination centers even after crystallization. Therefore, it is desirable not only to use a high-purity material gas but also to use an ultrahigh vacuum-compatible CVD apparatus equipped with a mirror surface treatment (electropolishing treatment) in the reaction chamber and an oil-free vacuum exhaust system.
[0272]
Next, the semiconductor film 3002 having an amorphous structure in the atmosphere or in an oxygen atmosphere is crystallized by irradiation with the first laser light using the laser device of the present invention. In this embodiment, continuous wave YVO is used as the first laser. _Four Use a laser. In this embodiment, the output energy of the laser beam is set to 27 W, the laser beam spot is formed into an elliptical shape having a major axis × minor axis of 500 μm × 50 μm, and the laser beam is moved in the minor axis direction of the ellipse. Note that the output energy of the laser light and the shape of the beam spot can be set as appropriate by the designer.
[0273]
In this embodiment, continuous oscillation type YVO is used. _Four Although a laser is used, this embodiment is not limited to this configuration. For example, laser oscillation devices are pulse oscillation type or continuous emission type excimer lasers, YAG lasers, YVOs. _Four A laser can be used. Crystallization conditions are appropriately selected by the practitioner. When an excimer laser is used, the pulse oscillation frequency is 300 Hz and the laser energy density is 100 to 400 mJ / cm. ² (Typically 200-300mJ / cm ² ). When a YAG laser is used, the second harmonic is used and the pulse oscillation frequency is set to 30 to 300 kHz, and the laser energy density is set to 300 to 600 mJ / cm. ² (Typically 350-500mJ / cm ² ) Then, laser light condensed linearly with a width of 100 to 1000 μm, for example 400 μm, is irradiated over the entire surface of the substrate, and the superposition rate (overlap rate) of the linear laser light at this time is 50 to 90%.
[0274]
As the laser, a continuous wave or pulsed gas laser or solid laser can be used. There are excimer laser, Ar laser, Kr laser, etc. as gas laser, and YAG laser, YVO as solid laser. ₄ Laser, YLF laser, YAlO ₃ Laser, glass laser, ruby laser, alexandry G Laser, Ti: sapphire laser, Y ₂ O ₃ A laser etc. are mentioned. Solid lasers include YAG, YVO doped with Cr, Nd, Er, Ho, Ce, Co, Ti, Yb or Tm. ₄ , YLF, YAlO ₃ Lasers using crystals such as 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.
[0275]
In crystallization of the amorphous semiconductor film, in order to obtain a crystal with a large grain size, it is preferable to use a solid-state laser capable of continuous oscillation and apply the second to fourth harmonics of the fundamental wave. Typically, Nd: YVO _Four It is desirable to apply the second harmonic (532 nm) or the third harmonic (355 nm) of the laser (fundamental wave 1064 nm). Specifically, continuous output YVO with an output of 10 W _Four Laser light emitted from the laser is converted into a harmonic by a non-linear optical element. 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.
[0276]
By irradiation with laser light, the semiconductor film 3002 having an amorphous structure is crystallized, and a semiconductor film 3003 having crystallinity and an oxide film 3004 in contact with the semiconductor film 3003 are formed. Note that a protruding portion (ridge) 3005 is formed along the crystal grain boundary of the semiconductor film 3003 when the laser light is irradiated. (Fig. 25 (B))
[0277]
Next, the oxide film 3004 is removed. In this embodiment, the oxide film 3004 is removed using a hydrofluoric acid-based etching solution, and the surface of the semiconductor film 3003 having crystallinity is exposed. Note that the method for removing the oxide film 3004 is not limited to the above-described method. For example, the oxide film 3004 may be removed using a fluorine-based gas.
[0278]
Next, the semiconductor film 3003 having crystallinity is irradiated with laser light (second laser light) in nitrogen or a vacuum atmosphere (FIG. 25C). Note that in the case where the second laser light is irradiated in an inert atmosphere, for example, as illustrated in FIG. 26, the inert gas may be irradiated only on a portion of the semiconductor film 3003 irradiated with the laser light. For example, as shown in FIG. 26A, laser light output from the laser oscillation device and the optical system 4001 may be irradiated to the semiconductor film 3003 through the slit of the gas blowing portion 4002. FIG. 26B is an enlarged view of the gas blowing portion 4002, and the gas blowing portion 4002 is provided with a slit 4006 through which laser light can pass. In addition, the gas blowing portion 4002 is provided with an opening 4008 that allows the inert gas supplied through the conduit 4007 to be sprayed to the periphery of the semiconductor film 3003 where the laser light is irradiated. The inert gas injected from the opening 4008 is blown to the semiconductor film 3003.
[0279]
When the laser beam (second laser beam) is irradiated by the second laser beam irradiation, the height difference (PV value: Peak to Valley, height of the unevenness formed by the first laser beam irradiation) A difference between the maximum value and the minimum value) is reduced, that is, a planarized semiconductor film 3006 is formed. Here, the PV value of the unevenness may be observed with an AFM (atomic force microscope). Specifically, when the PV value of the unevenness on the surface formed by the irradiation of the first laser beam is, for example, about 10 nm to 30 nm, the uneven PV on the surface by the irradiation of the second laser beam. The value can be 5 nm or less.
[0280]
As this laser light (second laser light), excimer laser light having a wavelength of 400 nm or less, and second and third harmonics of a YAG laser are used. Further, the same laser as the first laser beam described above may be used.
[0281]
Note that the irradiation with the second laser light is higher than the energy density of the first laser light, but the crystallinity hardly changes before and after the irradiation. Also, the crystal state such as the grain size hardly changes. That is, it seems that only the flattening is performed by the irradiation of the second laser beam.
[0282]
The merit that the semiconductor film 3006 having crystallinity is planarized by irradiation with the second laser light is very large. Specifically, the improvement in flatness enables a gate insulating film to be formed later to be thinned, so that the on-current value of the TFT can be improved. In addition, when flatness is improved, off current can be reduced when a TFT is manufactured.
[0283]
This embodiment can be implemented in combination with Embodiments 1 to 16.
[0284]
【The invention's effect】
The laser apparatus of the present invention sets the irradiation position of the laser beam on the object to be processed in the X direction and the Y direction without changing the moving direction of the object to be processed even if the laser beam is irradiated from a certain position and a certain direction The entire surface of the object to be processed can be irradiated with laser light. Therefore, there is no time loss associated with the change of the moving direction of the object to be processed, and the processing efficiency can be increased as compared with the conventional case.
[0285]
In addition, since the irradiation angle of the laser beam to the object to be processed is fixed regardless of the irradiation position, the intensity of the beam reflected and returning within the object to be processed, the intensity of interference, etc. vary depending on the irradiation position. Can be prevented, and the processing of the object to be processed can be performed almost uniformly. For example, when a semiconductor film is crystallized by laser irradiation, it is possible to prevent a difference in crystallinity depending on the position of the semiconductor film. In addition, the optical system can be simplified as compared with the case where the entire object to be processed is irradiated with laser light by changing the beam irradiation direction.
[Brief description of the drawings]
FIG. 1 is a diagram showing the structure of a laser device of the present invention.
FIG. 2 is a diagram showing a structure of a laser device of the present invention.
FIG. 3 is a diagram showing a direction in which an irradiation position of a laser beam moves in an object to be processed.
FIG. 4 is a diagram illustrating a structure of a laser device of the present invention and a diagram illustrating a direction in which an irradiation position of a laser beam moves in an object to be processed.
FIG. 5 is a diagram showing a position irradiated with laser light.
FIG. 6 is a diagram showing a position irradiated with laser light.
FIG. 7 is a diagram showing a structure of a laser device of the present invention.
FIG. 8 is a diagram showing a laser beam locus in a liquid crystal panel.
FIG. 9 is a diagram showing a position irradiated with laser light.
FIG. 10 is a diagram showing a structure of a laser device of the present invention.
FIG. 11 is a diagram showing a structure of a laser device of the present invention.
FIG. 12 is a view showing a structure of a laser device of the present invention.
FIGS. 13A and 13B illustrate a method for manufacturing a semiconductor device using a laser apparatus of the present invention. FIGS.
FIGS. 14A to 14C illustrate a method for manufacturing a semiconductor device using the laser apparatus of the present invention. FIGS.
FIGS. 15A to 15C illustrate a method for manufacturing a semiconductor device using a laser apparatus of the present invention. FIGS.
FIGS. 16A to 16C illustrate a method for manufacturing a semiconductor device using the laser apparatus of the present invention. FIGS.
FIGS. 17A to 17C illustrate a method for manufacturing a semiconductor device using a laser apparatus of the present invention. FIGS.
FIGS. 18A to 18C illustrate a method for manufacturing a semiconductor device using the laser apparatus of the present invention. FIGS.
FIG 19 is a diagram showing a method for manufacturing a semiconductor device using a laser apparatus of the present invention.
FIG. 20 is a diagram showing the direction in which the irradiation position of laser light moves in a conventional object to be processed.
FIGS. 21A to 21C illustrate a method for manufacturing a semiconductor device using a laser apparatus of the present invention. FIGS.
FIG. 22 is a block diagram of the laser apparatus of the present invention.
FIG. 23 shows a method for irradiating a liquid crystal panel with laser light.
FIG. 24 is a diagram of an electronic device using a semiconductor device of the invention.
FIG. 25 is a view showing a method for crystallizing a semiconductor film using the laser apparatus of the present invention.
FIG. 26 is a diagram showing an embodiment of a laser apparatus of the present invention.

Claims (17)

Forming a semiconductor film on a plurality of substrates,
Processing the laser beam output from the laser oscillator using an optical system,
While rotating the turntable installed the plurality of board, illuminated by moving the center of the rotary stage rotation linearly, yet the processed laser light in a certain region in the movement range of the semiconductor film By increasing the crystallinity of the semiconductor film,
The method of manufacturing a semiconductor device, wherein the certain region exists on an extension of the straight line. Patterning semiconductor films formed on multiple substrates to form island-shaped semiconductor films,
Processing the laser beam output from the laser oscillator using an optical system,
While rotating the turntable installed the plurality of substrates, certain regions in the movement range of the center of the turntable rotation is moved linearly, yet the processed the laser light island-shaped semiconductor film To increase the crystallinity of the island-shaped semiconductor film,
The method of manufacturing a semiconductor device, wherein the certain region exists on an extension of the straight line. In claim 2,
A method for manufacturing a semiconductor device, wherein the laser light is irradiated from an edge of the patterned semiconductor film. Forming a semiconductor film on a plurality of substrates,
Processing the laser beam output from the laser oscillator using an optical system,
While rotating the turntable installed the plurality of board, illuminated by moving the center of the rotary stage rotation linearly, yet the processed laser light in a certain region in the movement range of the semiconductor film By increasing the crystallinity of the semiconductor film,
Patterning the semiconductor film with increased crystallinity to form an island-shaped semiconductor film;
The method of manufacturing a semiconductor device, wherein the certain region exists on an extension of the straight line. In any one of Claims 1 thru | or 4,
The n-th (n + 1) -th laser beam trajectory irradiates the semiconductor film and the (n + 1) -th laser beam trajectory overlap each other, and the n-th laser beam edge and the (n + 1) -th laser beam trajectory overlap each other. A method for manufacturing a semiconductor device, wherein edges of laser beams do not overlap each other. In any one of Claims 1 thru | or 5,
A method for manufacturing a semiconductor device, comprising: disposing a reflector below the semiconductor film; and irradiating a laser beam reflected by the reflector from a back surface of the semiconductor film. In any one of Claims 1 thru | or 6,
The method for manufacturing a semiconductor device, wherein an incident angle of the laser beam to the semiconductor film is 5 to 30 °. In any one of Claims 1 thru | or 7,
The method for manufacturing a semiconductor device, wherein the laser oscillation device uses a continuous wave laser. In any one of Claims 1 thru | or 7,
The method for manufacturing a semiconductor device, wherein the laser oscillation device uses a solid-state laser. In claim 9,
The solid-state laser is a YAG laser, a YVO ₄ laser, a YLF laser, a YAlO ₃ laser, a glass laser, a ruby laser, an alexandrite laser, a Ti: sapphire laser, or a Y ₂ O ₃ laser. Method. In any one of Claims 1 thru | or 7,
The method for manufacturing a semiconductor device, wherein the laser oscillation device uses an excimer laser, an Ar laser, or a Kr laser. In any one of Claims 1 to 11,
A method for manufacturing a semiconductor device, comprising combining laser beams output from a plurality of the laser oscillation devices and irradiating the semiconductor film. In any one of Claims 1 to 11,
A method for manufacturing a semiconductor device, comprising: dividing a laser beam output from the laser oscillation device and irradiating the semiconductor film. In any one of Claims 1 thru / or Claim 13,
The method for manufacturing a semiconductor device, wherein the laser beam is a second harmonic. In any one of Claims 1 thru | or 14,
A method for manufacturing a semiconductor device, characterized in that a speed of moving the center of rotation is kept constant. In any one of Claims 1 to 15,
A method for manufacturing a semiconductor device, characterized in that an angular velocity of the rotation increases as the center of rotation approaches the certain region. In any one of Claims 1 thru | or 16,
The incident angle θ of the laser beam is defined as W when the width of the laser beam at the intersection of the plane of incidence of the laser beam and the plane is W, and d as the thickness of the substrate having the insulating surface.
θ ≧ arctan (W / 2d)
A method for manufacturing a semiconductor device, wherein:

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