JP4524413B2 - Crystallization method - Google Patents

Description

  The present invention relates to a substrate to be processed, a thin film transistor, and a display device used for a display device such as a liquid crystal or an organic EL, and more particularly to a crystallization method and a crystallization device used for them.

  A driving circuit of a display device such as a liquid crystal display device is formed on a polycrystalline semiconductor film such as an amorphous semiconductor film formed on a glass substrate. Since information handled by the expansion of the IT market is digitized and speeded up, a display device for displaying such information is also required to have high image quality. As means for satisfying this requirement, for example, by forming a switching transistor for switching each pixel in the crystal region, the switching speed is increased, and the image quality can be improved.

As a means for crystallizing a non-single crystal semiconductor film such as an amorphous silicon layer formed on a glass substrate, an excimer laser annealing method (ELA method) is known. However, the grain size of crystals obtained by this ELA method is about 0.1 μm, and when a thin film transistor (TFT) is formed in this crystallized region, a large number of crystal grains are formed in the channel region of one thin film transistor. will be field exists, mobility 200 cm ² / Vs, the on-off current ratio and extent ^107, inferior considerably when compared to MOS transistor formed in the single crystal Si. Variations in the characteristics of each thin film transistor occur due to variations in the number of crystal grain boundaries, and in particular, there is a problem that is not suitable for display devices that require uniform display within one screen.

  The present inventors have developed a technique for forming crystal grains large enough to form at least one thin film transistor by irradiating the amorphous silicon layer with laser light. By forming a TFT in a single crystal grain, there is no adverse effect of crystal grain boundaries, TFT characteristics are greatly improved, and functional elements such as a processor, a memory, and a sensor can be formed. As such a crystallization method, for example, there are crystallization methods described in Non-Patent Document 1 and Non-Patent Document 2.

The former Non-Patent Document 1 irradiates an amorphous silicon film with a phase-modulated laser beam of 0.8 J / cm ² through a cap film made of SiON / SiO ₂ film or a cap film made of SiO ₂ film. Thus, there is described a method of crystallizing an amorphous silicon film by laterally growing crystal grains in a direction parallel to the cap film.

Further, in the latter non-patent document 2, the amorphous silicon film is irradiated with a homogenized and phase-modulated laser beam through a cap film made of a SiO ₂ film under substrate heating. A method for crystal growth of the molten region in the lateral direction is described.
W. Yeh and M.M. Matsumura Jpn. Appl. Phys. Vol. 41 (2002) 1909. Proceedings of the 63rd Japan Society of Applied Physics, Autumn 2, 2002, p779, 26a-G-2. Masato Hiramatsu and others

  However, in the method of Non-Patent Document 1, a crystal grain having a large grain size of 10 μm or more can be obtained, but a small crystal grain having a small grain size is generated in the vicinity of the crystal grain having a large grain size. Therefore, there is a demand for aligning crystal grains having a large grain size as a whole film structure and forming them relatively uniformly (that is, densely).

  In addition, in the methods of Non-Patent Documents 1 and 2, there is a demand for further low temperature or room temperature treatment with respect to the substrate temperature in order to increase the crystal grain size. For example, in the conventional crystallization apparatus 100 shown in FIG. 20, the laser beam 50 is irradiated while heating the substrate 5 to a high temperature region by the heater 101 built in the mounting table 6. The heater 101 is supplied with power from the power source 102 controlled by the controller 103 and has a capability of heating the substrate 5 to a temperature range of 300 to 750 ° C.

  Since the substrate heating temperature may exceed 500 ° C., for example, general-purpose glass (for example, soda glass), plastics, etc. are likely to be altered or deformed by heating, and these general-purpose glasses are used as substrates for liquid crystal display devices (LCD). For this, low temperature treatment is an essential condition. In addition, there is a strong demand for weight reduction in large-screen LCDs, so there is a tendency to reduce the thickness of the substrate, which tends to cause deformation by heating, and low-temperature processing is an indispensable condition to ensure flatness of thin substrates. .

  The present invention has been made in order to solve the above-described problem, and a crystallization method, a crystallization apparatus, which can form large-sized crystal grains densely and can satisfy the requirements for low-temperature treatment, It is an object to provide a thin film transistor and a display device.

  As a result of diligent research regarding the formation of crystal grains that are large enough to form at least one thin film transistor, the present inventors have not been able to increase the crystal grains densely by irradiation with conventional parallel pulse laser light. I got the knowledge. The cause is not clarified in a strict sense, but it is presumed to be as follows.

  FIG. 21 is a characteristic curve diagram showing the optical intensity distribution after the optical system composed of the phase shifter 4 and the substrate 5 having the non-single crystal semiconductor layer, and the parallel pulse laser beam transmitted through the phase shifter 4. In this light intensity distribution, the components from the first reverse peak wave 91 to the next peak wave 92 contribute to lateral growth. On the other hand, the higher order vibration wave 93 outside this waveform has crystal nuclei generated by the reverse peak wave. It has been found that since fine crystal grains are generated, the entire film cannot be uniformly and densely crystallized with a large grain size. That is, with parallel pulse laser light (light that has not been homogenized), it has been found that large-grain crystal grains cannot be densely formed because the light obtained by phase modulation of the laser light includes high-order vibrations 93. did.

  According to the crystallization method of the present invention, a homogenized pulse laser beam is incident on a non-single-crystal semiconductor film through a silicon oxide film as a phase modulation optical system and an insulating film, so that relatively large crystal grains are densely packed. Can be formed side by side. In other words, by irradiating the non-single crystal semiconductor film with laser light that has passed through a phase modulation optical system having a light intensity distribution BP as shown in FIG. Crystal grains having a diameter can be formed in a dense (uniform) arrangement. The light intensity distribution BP shown in FIG. 1B is a light intensity distribution of a V-shaped groove as shown in FIG. This light intensity distribution BP has a plurality of peak patterns having an inverted triangular cross section. The light intensity distribution of each inverted triangular peak pattern has the same amplitude PH and the same pitch interval PW. The phase modulation optical system is, for example, a phase shifter.

  Further, the solidification start temperature of the melted portion of the non-single-crystal semiconductor film irradiated with the laser light has a physical property value specific to the target semiconductor film. From this, the present inventors considered that the starting fluence of lateral growth is a numerical value unique to the semiconductor film, and found that it was a substantially constant value regardless of the fluence of the pulse laser. Further, the end of the lateral growth is not only when the cooling rate becomes faster than the growth rate and new nucleation occurs in the growth direction, but also the cap film or the semiconductor film is peeled off by instantaneous heating. We found out that it is also caused by physical factors. In particular, the occurrence of peeling is found to occur when the semiconductor film is peeled off when more energy is present in the semiconductor film, and the presence of a flat portion in the reverse peak pattern greatly contributes to peeling. It was.

  In addition, as a result of evaluating the substrate temperature dependence of the lateral growth distance using the generation of the optimal cross-section inverted triangular pattern inverted peak pattern light by the phase modulation optical system and the appropriate heat storage effect of the cap film, as shown in FIG. It has been found that Si crystal grains having a large particle size can be obtained even at room temperature. The optimum cross-section inverted triangular inverted peak pattern light optimizes the maximum and minimum values of the inverted inverted triangle inverted peak pattern and sufficiently increases the distance between the maximum values.

  This invention is made | formed based on this knowledge, and has the following structures.

The crystallization method according to the present invention is a laser device in which the timing for oscillating the laser beam is controlled, and is arranged on the same optical axis as the laser beam oscillated from the laser device, and makes the light intensity of the incident laser beam uniform. Homogenizer, a spatial intensity modulation optical element disposed on the same optical axis as the homogenizer, a mounting table for mounting a substrate to be processed provided in the optical path of the laser beam, and a mounting table on the mounting table Using a projection type crystallization apparatus having an imaging optical system disposed between a substrate to be processed and the spatial intensity modulation optical element, laser light is applied to a non-single crystal semiconductor film provided on the substrate to be processed. A crystallization method for crystallizing by irradiation,
A cap film is provided on the laser light incident surface of the non-single crystal semiconductor film,
By irradiating the non-single crystal semiconductor film with the laser beam having a light intensity distribution having a cross-section inverted triangular peak pattern that repeats monotonous increase and decrease through the cap film, only the irradiated portion is melted and temperature drop is started. After that, the solidification of the reverse peak point that becomes the minimum of the irradiation part starts, and the solidification point moves according to the gradient of the cross-section inverted triangular peak pattern, and the crystal grows in the lateral direction,
The irradiation position by the laser beam from the mounting table and the laser device is relatively moved to crystallize a predetermined region of the non-single crystal semiconductor film, thereby minimizing the laser beam irradiation portion. It is characterized by crystallization from the reverse peak point .

  A crystallization apparatus according to the present invention is a crystallization apparatus for crystallization by irradiating a non-single crystal semiconductor film with a laser beam, on which a laser light source and a substrate having the non-single crystal semiconductor film are placed. And a homogenizer that is provided between the mounting table and the laser light source and homogenizes the laser light with respect to an incident angle and light intensity, and is provided between the homogenizer and the mounting table, and is homogenized by the homogenizer. And a phase modulation optical system having a plurality of portions for phase-modulating the laser beam.

  A substrate to be processed according to the present invention is provided on a substrate made of at least one material of an insulator, a semiconductor, and a metal, a first insulating layer provided on the substrate, and the first insulating layer. An amorphous semiconductor film or a non-single crystal semiconductor film, and a second insulating layer having a thickness of 150 nm to 350 nm provided on the amorphous semiconductor film or the non-single crystal semiconductor film. It is characterized by. The first insulating layer and the second insulating layer are optimally silicon oxide films.

  A thin film transistor according to the present invention is a pixel of a display device and a thin film transistor that drives the pixel, and a silicon oxide film is formed as a cap film on an insulating substrate and a non-single crystal semiconductor film formed on the substrate. Then, laser light having a light intensity distribution having a plurality of cross-section inverted triangular peak patterns is incident from the silicon oxide film, and the laser light reaches the non-single-crystal semiconductor film through the silicon oxide film. Melting the non-single crystal semiconductor film and storing heat in the silicon oxide film provided on the laser light incident surface of the non-single crystal semiconductor film to delay the solidification rate of the non-single crystal semiconductor film, A channel region formed in a crystal grain of a large grain size formed by crystallizing the film in the lateral direction, and the channel region sandwiched between the channel region, A source region and a drain region doped with impurities, a gate insulating film formed on the channel region, a gate electrode formed on the gate insulating film, and an interlayer insulating film covering the gate electrode And a source electrode conducting from the interlayer insulating film side to the source region, and a drain electrode conducting from the interlayer insulating film side to the drain region.

  The display device according to the present invention includes a pair of substrates bonded to each other through a predetermined gap, and an electro-optical material held in the gap, and a counter electrode is formed on one of the substrates, and the other substrate The display device includes a pixel and a thin film transistor that drives the pixel, wherein the thin film transistor includes an insulating substrate and a silicon oxide film as a cap film on the non-single crystal semiconductor film formed on the substrate. The laser light having a light intensity distribution having a plurality of cross-section inverted triangular peak patterns is incident from the silicon oxide film, and the laser light is incident on the non-single-crystal semiconductor film through the silicon oxide film. The non-single-crystal semiconductor film is melted and is stored in the silicon oxide film provided on the laser light incident surface of the non-single-crystal semiconductor film to solidify the non-single-crystal semiconductor film. A channel region formed in a crystal grain region having a large grain size formed by delaying the degree of crystallization and laterally crystallizing the non-single-crystal semiconductor film, and sandwiching the channel region, A source region and a drain region doped with impurities; a gate insulating film formed on the channel region; a gate electrode formed on the gate insulating film; an interlayer insulating film covering the gate electrode; A source electrode conducting from the interlayer insulating film side to the source region and a drain electrode conducting from the interlayer insulating film side to the drain region are provided.

  In the present specification, the “phase shifter” is an example of a phase modulation optical system, refers to a spatial intensity modulation optical element for modulating the phase of laser light, and is used in an exposure step of a photolithography process. It is distinguished from a phase shift mask. By introducing a progressive design concept into the phase shifter, a one-dimensional light intensity distribution BP schematically shown in FIG. 2A can be obtained. That is, it is possible to obtain light intensity distributions BP having different intensity inclination angles θ, pitch widths PW, and bias intensity PH (intensities at valleys). The phase shifter is, for example, a step formed on a quartz substrate as a transparent body. The step of the phase shifter is formed by a process such as etching so that incident light is phase-modulated to a predetermined phase angle, for example, 180 °.

In the present invention, the pulse laser beam having the optimized light intensity distribution, that is, the pulse laser beam shown in FIG. 1B, FIG. 14A, and FIG. A semiconductor film (amorphous film or polycrystalline film) to be crystallized is irradiated through a silicon oxide film. As shown in FIG. 5, a non-single crystal semiconductor film to be crystallized, such as an amorphous silicon film 52, is heated by irradiation with pulsed laser light 50, and its temperature (T _Si ) is high at the end of the pulse. During the pulse irradiation, heat generated in the amorphous silicon film 52 to be crystallized is transferred to, for example, a low-temperature silicon oxide film (SiO ₂ film) provided as the cap film 53 in the initial stage. After the pulse irradiation is completed (after the laser beam irradiation is cut off), the amorphous silicon film 52 to be crystallized starts to be cooled, and the heat accumulated in the cap film 53 is converted to the amorphous silicon film to be crystallized. It is diffused toward the film 52. Thus, the cap film 53 works predominantly as a heat capacitor, and the high-temperature liquid phase state of the amorphous silicon film 52 can remain longer than the case without the cap film 53.

  However, the cap film 53 returns only a part of the heat transferred from the molten amorphous silicon film 52, but still retains a large amount of heat inside. For this reason, the molten amorphous silicon film 52 is supplied with heat from the cap film 53, and the solidification start time of the molten amorphous silicon film 52 can be delayed. As a result, the lateral growth distance of the crystal grains increases. The crystal grains having large grain diameters are densely arranged. The supply of heat from the cap film 53 varies greatly depending on the film thickness of the cap film 53. That is, according to the method of the present invention, the cooling rate of the semiconductor film is moderated by the silicon oxide film that is the heat-storing cap film 53 in contact with the amorphous silicon film that is the semiconductor film, and the room temperature can be obtained without heating the substrate. In this case, a single crystal or a crystal grain having a large grain size close to that can be obtained.

The film thickness of the cap film 53 is preferably 30 nm or more and 500 nm or less from the viewpoint of heat storage characteristics, and is most preferably 100 nm or more and 370 nm or less (see FIGS. 11 and 22). When the film thickness is less than 30 nm, the heat storage amount of the SiO ₂ cap film becomes insufficient, and large crystal grains having a desired size cannot be obtained. On the other hand, if the film thickness exceeds 500 nm, the heat transfer amount (heat dissipation amount; heat diffusion amount) in the thickness direction from the crystallization target film (non-single-crystal semiconductor film) to the SiO ₂ cap film 53 increases, so You will not be able to achieve your objectives sufficiently.

  Further, the pulse laser beam is made uniform with respect to the incident angle by the first fly-eye lens and the first condenser optical system as a homogenizing optical system (homogenizer), and further the second fly-eye lens and the second condenser optical. It is desirable that the light intensity be made uniform by the system. When the laser beam that has been made uniform with respect to the incident angle and the light intensity as described above is transmitted through the phase shifter 4 in FIG. 1 (a), the light intensity increases and decreases monotonously as shown in FIG. 1 (b). Light intensity distribution BP. The light intensity distribution BP in FIG. 1B has an inverted triangular cross section, the maximum peak value and the minimum peak value are projecting, and have no flat portion. Moreover, it has an equal amplitude PH and an equal pitch interval PW. That is, since the phase-modulated homogenized laser beam does not contain a high-order vibration component, when it is irradiated onto the film to be crystallized, the size of the phase shifter 4a-4a is theoretically the size corresponding to the width interval W. Large grains can be laterally grown. At this time, heat energy is replenished to the film to be crystallized by the heat storage effect of the insulating layer, so that a series of processes of melting → solidification crystallization → grain lateral growth is promoted, and the size of the crystal grains is increased. Note that in the light intensity distribution BP of FIG. 1B, when the angle θ of the peak portion becomes gentle, the non-single crystal semiconductor film is liable to break down. Therefore, the angle θ of the peak portion is as sharp as possible. It is desirable to set the intensity distribution BP.

  According to the present invention, a Si crystal grain having a large particle size can be formed by room temperature treatment, and the requirement for low temperature treatment can be satisfied. Therefore, a thinner glass substrate or plastic substrate than the conventional one can be used as the substrate. Is possible.

  Further, according to the present invention, dense crystal grains having a large grain size can be formed side by side over the entire film, so that a TFT for a large screen LCD that operates fast and has little variation in threshold voltage is manufactured. Is possible.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In FIG. 1 to FIG. 19, the same parts are denoted by the same reference numerals, and detailed description thereof will be omitted when overlapping. As shown in FIG. 3, the crystallization apparatus 10 includes an optical system 2a, 2b, a homogenizer 3, an imaging optical system 43, in which pulsed laser light 50 oscillated from the KrF excimer laser apparatus 1 is sequentially provided in the optical path. The substrate 40 on the mounting table 6 is irradiated through the phase shifter 4 to be crystallized. The power supply circuit of the KrF excimer laser device 1 is connected to the output unit so that the output signal of the controller 8 is supplied. The controller 8 controls the oscillation timing, pulse width, pulse interval, output magnitude, etc. of the laser beam 50.

  The optical system of this apparatus is one in which, for example, a concave lens 2a, a convex lens 2b, a homogenizer 3, a phase shifter 4 and the like are arranged on the same optical axis. The crystallization apparatus 10 is a proximity type optical system.

  The homogenizer 3 has a function of leveling the pulsed laser light in the irradiation region. That is, the incident angle and the light intensity of the pulsed laser beam 50 that has passed through the homogenizer 3 are homogenized. The homogenizer 3 is an optical system for homogenizing (homogenizing) the pulse laser beam 50 with respect to the incident angle and the light intensity.

  Further, the homogenized pulse laser beam 50 is phase-modulated by the phase shifter 4. For example, the phase shifter 4 is a line-and-space type (in-plane-cross-coupled type) having a plurality of linear steps 4 a arranged in parallel and close to the substrate 40 to be processed on the mounting table 6. It is a proximity type crystallizer arranged. The phase shifter 4 is made of a transparent body, and causes a phase difference in the pulse laser beam 50 at the step 4a. The phase shifter 4 causes Fresnel diffraction in the pulse laser beam 50 due to the above phase difference, and modulates the light intensity of the pulse laser beam 50. As a result, as shown in FIG. 1B, the phase shifter 4 forms a light intensity distribution BP having a repetitive pattern in which the monotonous increase and the monotonous decrease are repeated in the irradiated portion. In the present embodiment, the interval W between the steps 4a-4a of the phase shifter 4 is set to 100 μm. In the proximity-type crystallization apparatus, the cap film 53 for increasing the particle size outputs a good heat storage effect when the film thickness is 30 nm or more and 500 nm or less. Therefore, in the proximity type crystallization method, the optimum film thickness of the cap film 53 is not less than 30 nm and not more than 500 nm.

  For example, a cap film 53 is provided on the upper surface of the substrate to be processed. The distance between the cap film 53 and the phase shifter 4 is set to a predetermined interval of, for example, 500 μm or less. Peripheral devices other than the loading table 6 and the mounting table 6 are not provided with a substrate heating mechanism (such as a built-in heater).

  The mounting table 6 is mounted on an XYZθ stage 7, is movable in the X-axis and Y-axis directions in the horizontal plane, is movable in the Z-axis direction orthogonal to the horizontal plane, and is rotatable about the Z-axis. is there. The power supply circuit of the XYZθ stage 7 is connected to the output unit of the controller 8. The XYZθ stage 7 is provided with an X-axis drive mechanism, a Y-axis drive mechanism, a Z-axis drive mechanism, and a θ rotation drive mechanism, and the XYZθ stage 7 is controlled in the X, Y, Z, and θ directions, respectively. ing. The above example is a crystallization method using a proximity type optical system, but may be a crystallization method using a projection type optical system. In the projection type crystal method, the optimum film thickness of the cap film 53 is not less than 80 nm and not more than 400 nm.

Next, the crystallization method by the proximity type crystallization apparatus 10 shown in FIG. 3 will be described. A pulse laser beam having a pulse width of, for example, 30 nsec and a light intensity of, for example, 1 J / cm ² is emitted from the pulse laser light source 1. The pulsed laser light is diverged and converged by the concave lens 2 a and the convex lens 2 b and is incident on the homogenizer 3. The homogenizer 3 homogenizes the incident angle and light intensity of the incident pulse laser beam 50.

  The homogenizer 3 causes the uniformed pulsed laser light 50 to enter the phase shifter 4, and the phase shifter 4 emits pulsed laser light having a light intensity distribution with a cross-section inverted triangular reverse peak pattern. At this time, the maximum and minimum values of the cross-section inverted triangular inverted peak pattern are designed to values defined by the type and film thickness of the non-single-crystal semiconductor film. The homogenized pulsed laser beam having a light intensity distribution with a reverse peak pattern having an inverted triangular cross section is incident on the amorphous silicon film 52, and only the irradiated portion is melted and crystallized. Since the amorphous silicon film 52 is thin, it immediately melts in the thickness direction at the irradiated portion, and the temperature of the melted portion is started to start from the reverse peak point at which the fluence is minimized, and solidification (crystallization) starts. In this solidification position, the solidification point sequentially moves in accordance with the gradient of the reverse peak pattern having an inverted triangular cross section. By this movement of the freezing point, crystal grains grow in the lateral direction (direction orthogonal to the thickness of the amorphous silicon film 52). In the lateral growth of the crystal grains, since the temperature drop gradient is maintained over a long period of time due to the heat storage effect of the cap film 53, the crystallization is promoted. Single crystallization is realized.

  Such a crystallization process is performed in a predetermined region of the amorphous silicon film 52. The means for performing the crystallization process over the entire surface can be performed by relatively moving the stage 7 and the irradiation position by the pulse laser light source 1.

  Next, the optical system will be specifically described with reference to FIG. FIG. 4 is a configuration diagram of the proximity optical system. For example, a KrF excimer laser light source 1 that emits excimer pulse laser light with a wavelength of 248 nm is provided as the pulse laser light source 1. The light source 1 may be another light source such as a XeCl excimer pulse laser light source or a YAG laser light source. The laser light emitted from the light source 1 is enlarged through optical systems 2 a and 2 b including a beam expander 2 and then enters the first fly-eye lens 33.

  A plurality of light sources are formed on the rear focal plane of the first fly-eye lens 33, and light beams from the plurality of light sources enter the second fly-eye lens 35 via the first condenser optical system 34. Illuminate the surface in a superimposed manner. As a result, more light sources are formed on the rear focal plane of the second flyer lens 35 than on the rear focal plane of the first fly-eye lens 33. The light beam from the light source formed on the rear focal plane of the second fly-eye lens 35 illuminates the phase modulation optical system 4 (phase shifter) in a superimposed manner via the second condenser optical system 36.

  Here, the first fly-eye lens 33 and the first condenser optical system 34 constitute a first homogenizer, and the incident angle on the phase shifter 4 is made uniform by the first homogenizer.

  The second fly-eye lens 35 and the second condenser optical system 36 constitute a second homogenizer, and the second homogenizer makes uniform the light intensity (laser fluence) at each position in the plane on the phase shifter 4. Is achieved. In this way, the illumination system irradiates the phase shifter 4 with light having a substantially uniform light intensity distribution (light intensity distribution).

[Example]
The amorphous silicon film 52 was crystallized by irradiating one surface of the substrate 40 with a phase-modulated pulsed laser beam homogenized using the proximity-type crystallization apparatus 10 shown in FIG. The substrate 40 to be processed is obtained by forming a silicon oxide film as the cap film 53 as shown in FIG. That is, the substrate 40 is a structure in which an insulating layer such as a base protective film 51, an amorphous silicon film 52, and a cap film 53 are sequentially stacked on a base made of an insulator or a semiconductor such as a silicon substrate 48. It is. The base protective film 51 is made of a first insulating layer having a film thickness of 1000 nm, for example, insulating SiO ₂ . The amorphous silicon film 52 is a film to be crystallized, and is made of, for example, amorphous silicon having a thickness of 200 nm. The cap film 53 is a second insulating layer, for example, insulating SiO ₂ having a thickness of 300 nm.

  A method for manufacturing the substrate to be processed 40 having such a cap film 53 to be crystallized will be described more specifically.

A silicon substrate 48 was used as a base made of an insulator or a semiconductor, and a base protective film 51 made of SiO _{2 having} a thickness of 1000 nm was formed by a thermal oxidation method.

  An amorphous semiconductor film or a non-single crystal semiconductor such as an amorphous silicon film 52 (for example, an amorphous Si film having a thickness of 200 nm formed by plasma chemical vapor deposition) is formed on the base protective film 51. .

Moreover the formation of the second insulating layer such as SiO ₂ film as a cap film 53 (e.g., SiH ₄ and N ₂ O and the plasma chemical vapor deposition SiO ₂ film having a thickness of 300nm was deposited by) the. Next, dehydrogenation treatment was performed on the thin films 51 to 53 formed on the silicon substrate 48. This treatment is desirably performed in a temperature range of 500 to 600 ° C., for example, heat treatment was performed at 570 ° C. × 2 hours in a nitrogen atmosphere.

  FIG. 6 is a photograph of an SEM image of a Si thin film crystallized at room temperature by the method of this embodiment. As is apparent from the observation of the SEM image, it was confirmed that a Si crystal having a large crystal grain size was formed by lateral growth in the range of 4 to 5 μm on one side from the laser optical axis (the center of the photograph). In addition, it was confirmed that the laterally grown Si crystals extended very well in the lateral direction starting from the central crystal nucleus and were aligned closely.

  After irradiating the pulse laser beam for one shot, the substrate was moved in parallel by a predetermined pitch distance, and the substrate was irradiated with the pulse laser beam of the next shot to obtain a Si crystal having a large crystal grain size by lateral growth. By repeating the same operation, the element formation region of the amorphous silicon film was crystallized one after another.

7 to 9 show the crystals when the phase shifter 4 is arranged in the proximity type crystallization apparatus 10 shown in FIG. 3 and the substrate 40 is irradiated with the pulse light of one-shot excimer laser at room temperature. The characteristic is shown. FIG. 7 shows a silicon oxide film (SiO ₂ film thickness (nm) as the cap film 53 on the horizontal axis and the lateral growth distance (μm) of crystallized crystal grains on the vertical axis. It is a characteristic view showing the result of examining the dependence of the lateral growth distance on the thickness of the cap film by changing the thickness of the silicon oxide film as the film 53. Note that the lateral growth distance was obtained as an average value. From the relationship of alignment accuracy with the channel portion of the transistor, a lateral growth distance of 4.0 μm or more was set as an acceptance criterion.

  As shown in FIG. 7, in the proximity type crystallization apparatus, when the thickness of the cap film 53 is 30 nm or more and about 340 nm or less, the lateral growth distance of 4 μm or more at the longest is obtained even at room temperature. It was. Further, even when the thickness of the cap film 53 is 30 nm and 80 nm, a lateral growth distance of about 3 μm or 2 μm at the longest is obtained. Even when the thickness of the cap film 53 was 390 nm, a lateral growth distance of about 1.5 μm at the longest was obtained. On the other hand, when the film thickness of the cap film 53 was 480 nm, the lateral growth distance was less than 1.5 μm. A crystallized region having a large grain size with a lateral growth distance of 5 μm or more is obtained when the thickness of the cap film 53 is 100 μm or more and 340 μm or less. The film thickness of the cap film 53 is such that the non-single crystal semiconductor film irradiated with the laser light through the phase shifter 4 is heated, and the temperature drop rate of the melted non-single crystal semiconductor film is slowed by the heating. Thus, the film thickness is such that crystallization with a large particle diameter can be obtained. In order to slow down the temperature drop rate, the cap film 53 (second insulating layer) is selected to have an appropriate thickness, and the light energy of the laser beam and the intensity distribution BP for crystallization are appropriately selected. is there.

In FIG. 8, the horizontal axis indicates the temperature (° C.) of the substrate 40 to be processed, and the vertical axis indicates the lateral growth distance (μm) of the crystallized crystal grains. As shown in FIG. The substrate temperature dependency of the lateral growth distance was investigated by changing the temperature of the substrate 40 to be processed having the cap film 53 made of a SiO ₂ film having a thickness of 300 nm as the cap film 53 placed in the Mitty crystallization apparatus 10. It is a characteristic view which shows the result. As is apparent from the figure, in the substrate to be processed 40 having the cap film 53 made of SiO ₂ having a sufficient thickness as the cap film 53, the substrate temperature is almost dependent on the substrate temperature of the lateral growth distance from room temperature to several hundred degrees Celsius. As a result, it was found that a sufficient lateral growth distance can be obtained even at room temperature. Although this phenomenon is not clear, it seems to be due to the heat storage effect of the cap film.

  In FIG. 9, the horizontal axis represents the light intensity index (relative amount), the vertical axis represents the lateral growth distance (μm) of the crystallized crystal grains, and the phase shifter 4 is a proximity type as shown in FIG. FIG. 6 is a characteristic diagram showing the result of examining the dependence of the lateral growth distance on the light intensity index by changing the light intensity of the laser light to various samples in various ways. As is clear from the figure, it was found that the lateral growth distance increases abruptly when the light intensity exceeds 0.9 in relative quantity. Specifically, a large lateral growth distance of 4 μm or more was obtained even by irradiating the substrate 40 to be processed with one-shot excimer pulse light at room temperature.

  In the present specification, the “light intensity index” means the energy light that can maintain the morphological characteristics of the film without breaking the film (crystal structure) even when subjected to various stresses during or after the growth of crystal grains. The light intensity value with respect to this reference is assumed. Here, “film breakdown” means that the regular structure (film structure) constituting the film is broken in a broad sense, and in a narrow sense, the cap film 53 is broken by stress generated when the crystal grains grow laterally. Or the crystallization target film is broken by the stress generated during the lateral growth, or defects such as cracks in the crystal grains or in the crystal grain boundaries due to hydrogen contained in the cap film 53 or the crystallization target film. Is defined to mean that

  From the above, using the method of the present invention, it was confirmed that it is possible to laterally grow large crystal grains (average crystal grain size 4 μm or more) at a high filling rate at room temperature.

  In the above embodiment, the example in which the phase shifter 4 is arranged in the proximity type has been described. However, the phase shifter 4 may be arranged in the projection type as shown in FIG. That is, the projection type crystallization apparatus 10A is an apparatus in which the imaging optical system 43 is disposed between the phase shifter 4 and the substrate 40 to be processed.

Next, an embodiment in which the Si film is crystallized by phase modulation excimer laser annealing (hereinafter abbreviated as PMELA) using the projection type crystallization apparatus 10A will be described. As shown in FIG. 5, a substrate 40 to be processed is formed by forming a base protective film 51 made of SiO ₂ having a thickness of 1000 nm on a silicon (Si) substrate 50 by a thermal oxidation method, and then forming amorphous silicon having a thickness of 200 nm. As the film 52 and the cap film 53, a SiO ₂ film 53 was sequentially laminated by a PE-CVD (Plasma Enhanced-CVD) method. Further, the amorphous Si film 52 and the cap film 53 may be formed by continuous film formation by PE-CVD (Plasma Enhanced-CVD) from the base protective film 51. Prior to PMELA, the substrate 40 was dehydrogenated at 550 ° C. for 2 hours in an annealing furnace in a nitrogen gas atmosphere.

  In PMELA, a substrate 40 to be processed was irradiated with a KrF excimer laser, for example, with a pulse width of 30 nsec and a single shot. Microstructural analysis of the crystallized Si film was performed by scanning electron microscope (SEM) after seco-etching. FIG. 2B is an example of a scanning electron microscope (SEM) image showing a sample crystallized by irradiating a single shot of pulsed laser light using a light intensity distribution BP with various pitch widths PW. It is.

  FIG. 11 and FIG. 12 show crystallization characteristics when the crystallization process of the substrate to be processed 40 is performed by the projection type crystallization apparatus 10A.

  FIG. 11 shows the result of examining the relationship between the lateral growth distance and the film thickness of the cap film 53 when the phase shifter 4 which is a phase modulation optical system is arranged in the projection type crystallization apparatus 10A as shown in FIG. FIG. That is, FIG. 11 is a diagram in which the horizontal axis represents the thickness (nm) of the cap film 53 and the vertical axis represents the lateral growth distance (μm) of the crystal grains. FIG. 11 shows the maximum lateral growth distance for each film thickness of the cap film 53. In addition, the curve in the figure connects the lateral growth distances at each cap film thickness. As apparent from FIG. 11, when the thickness of the cap film 53 increases, the lateral growth distance also increases. When the thickness of the cap film 53 is in the range of 130 to 400 nm, the lateral growth distance exceeds 4 μm. In particular, when the thickness of the cap film 53 is 250 nm, the lateral growth distance reaches a maximum of about 7 μm. As shown in FIG. 12, in this example, a large lateral growth distance of 6 μm or more was obtained when the substrate 40 was irradiated with excimer laser pulse light at room temperature.

  In FIG. 11, as reference data, the lateral growth distance of a sample, for example, a non-single crystal semiconductor film, without the cap film 53 is indicated by a black circle in the drawing. The lateral growth distance of the non-single crystal semiconductor film without the cap film 53 was shorter than the lateral growth distance of the non-single crystal semiconductor film with the cap film 53.

  FIG. 12 shows a phase shifter 4 with a light intensity index (relative value) on the horizontal axis and a lateral growth distance (μm) of crystal grains on the vertical axis in a 200 nm thick sample of the amorphous silicon film 52. FIG. 11 is a characteristic diagram showing the results of examining the relationship between the lateral growth distance of crystal grains and the light intensity when they are arranged in a projection type as shown in FIG. 10. As is clear from the figure, it was also confirmed by the projection method that the lateral growth distance increases abruptly when the light intensity exceeds 0.9 as a relative amount.

  Next, in the substrate to be processed 40 having the cap film 53 shown in FIG. 5, the crystallization process was performed while changing the film thickness of the amorphous silicon film 52, and the relationship with the maximum lateral growth distance was observed.

  FIG. 22 is a characteristic diagram showing the relationship between the film thickness of the amorphous silicon film 52 and the maximum lateral growth distance. Without the cap film 53, the maximum lateral growth distance was 2.5 μm when the film thickness of the amorphous silicon film 52 was 200 nm, as shown in FIGS. However, as shown in FIG. 21, in the target substrate 40 having the cap film 53 shown in FIG. 5, even when the amorphous silicon film 52 is as thin as 30 nm, for example, the lateral growth of 3 μm or more. Crystal grains are obtained. 7, 11, and 22, it has been found that the provision of the cap film 53 is effective in the maximum lateral growth distance.

  Further, in FIG. 22, when the thickness of the amorphous silicon film 52 is increased, the maximum lateral growth distance becomes longer, and when the thickness of the amorphous silicon film 52 is about 200 nm, the elongation of the maximum lateral growth distance is saturated. It shows that it comes.

Next, the conditions for the cap film thickness to achieve the maximum lateral growth distance shown in FIG. 22 will be described. FIG. 23 is a characteristic diagram showing the relationship between the film thickness d _a-Si of the amorphous silicon film 52 and the film thickness d _cap of the cap film 53 that achieves the maximum lateral growth distance. As a result, it has been found that the necessary film thickness d _{cap of the} cap film 53 increases as the film thickness d _a-Si of the amorphous silicon film 52 increases. FIG. 23 shows that as the amorphous silicon film 52 becomes thicker, the amount of heat in the silicon layer 52 increases, and a thick cap film 53 is necessary to store the increased heat. . In the characteristic diagram showing the relationship between the film thickness d _a-Si of the amorphous silicon film 52 and the film thickness d _cap of the cap film 53 in FIG. 23, the film thickness of the cap film 53 corresponds to the film thickness of each amorphous silicon film. correspondingly, straight d _cap = 0.568d _a-Si +60 and the straight line d _cap = 0.568d thickness of _a-Si respective amorphous silicon film 52 by being selected within the range surrounded by +160 d _a- The longest lateral crystal growth in _Si can be achieved. In the above formula, d _cap is the thickness (nm) of the second insulating layer (cap film 53), and d _a-Si is an amorphous semiconductor film or a non-single crystal semiconductor film (amorphous silicon film 52). ) Film thickness (nm).

[Verification test]
(Heat storage effect)
Next, the results of a verification test on the heat storage effect of the cap film 53 will be described with reference to FIGS. The verification test was conducted using a sample having a Si film thickness of 200 nm. 13 takes the average of the light intensity on the horizontal axis (mJ / cm ^2), crystal grains of the lateral growth length and the vertical axis represents the ([mu] m), a constant value pitch width PW of the light intensity distribution and (28 .mu.m) It is a characteristic view which shows the thermal storage effect of the cap film | membrane 53 when it did. In the figure, the white square indicates the result when the thickness of the cap film 53 is 130 nm, the white triangle indicates the result when the thickness of the cap film 53 is 220 nm, and the black circle indicates the thickness of the cap film 53 is 300 nm. The black triangles show the results when the thickness of the cap film 53 is 390 nm.

  In a thin cap film 53 such as a cap film 53 having a thickness of 130 nm (white square) and a thickness of 220 nm (white triangle), the lateral growth distance of crystal grains gradually increases as the light intensity increases until the film breakage occurs. Increased. The maximum lateral growth distance at this time was about 6 μm. In the case of the cap film 53 having a thickness of 300 nm (black circle) thicker than this, the lateral growth distance first increased to about 2 μm and then increased rapidly to exceed 6 μm. On the other hand, in the case of an extremely thick cap film 53 such as a thickness of 390 nm (black triangle), the lateral growth distance did not exceed 2 μm.

  FIGS. 14B and 14C show SEM images of the silicon film subjected to the crystallization process by irradiating the laser beam having the light intensity distribution schematically shown in FIG. FIG. 14B is an SEM image of the silicon film when the crystallization process is performed with the cap film 53 having a thickness of 300 nm. The arrow in FIG.14 (b) shows the direction of lateral growth. As a result of microscopic observation, the lateral growth distance exceeded 7 μm at the maximum value and was about 6 μm on the average value.

  FIG. 14C is an SEM image showing a crystallized form of a sample with a thick cap film 53 by Secco etching. In the figure, the lateral growth region is divided into several parts by the sintered crystal region. This indicates that a temperature gradient in the molten amorphous silicon film 52 can exist for a relatively long time. However, the temperature dropped sharply in front of the solid-liquid interface, below the critical temperature for spontaneous nucleation. Natural nucleation occurs near the front of the solid-liquid interface, and laterally growing crystal grains are stopped by mutual collision. At the same time, several new nuclei serve as the source of new lateral growth, such a situation often occurs when the temperature gradient in the molten amorphous silicon film 52 is more gradual and eventually uniform. Results in small grains. This effect becomes more remarkable as the cap film 53 becomes thicker. In the very thick cap film 53, since most of the heat amount of the Si layer is used to heat the cap film 53, the lifetime of the liquid phase of the Si layer is reduced.

  Further, it was confirmed that the lateral growth characteristics of the crystal clearly differ between the cap film 53 having a thickness of 220 nm and the cap film 53 having a thickness of 300 nm. In the sample with the cap film 53 having a thickness of 220 nm (substrate 40 to be processed), the crystal grain size increases with the light intensity. On the other hand, in the case of a cap sample with a cap film 53 having a thickness of 300 nm (substrate 40 to be processed), there was a critical strength at which the lateral growth characteristics of the crystal changed rapidly.

FIG. 15 is a schematic diagram for explaining this sudden change. In FIG. 15, the horizontal axis represents the position of each film layer on the substrate, and the vertical axis represents temperature (unitless), so that the amorphous silicon film 52 to be crystallized is formed on the SiO ₂ base protective film 51. FIG. 5 is a one-dimensional temperature distribution diagram showing a temperature distribution in a film thickness direction of a substrate to be processed 40 in which a SiO ₂ cap film 53 is formed on the amorphous silicon film 52. Here, it is assumed simply that the temperature T _Si of the amorphous silicon film 52 to be crystallized increases with time during pulse irradiation. Although the temperature distribution in the SiO ₂ cap film 53 and the base protective film 51 is the same at the end of the pulse of the laser beam irradiated in a pulsed manner, the temperature T of the amorphous silicon film 52 is schematically shown in the figure. Proportional to _Si . In the case of intense irradiation (solid line A), the temperature T _Si of the amorphous silicon film 52 becomes high, and as a result of the cap film 53 being heated by the temperature T _Si of the amorphous silicon film 52, The temperature exceeds the melting point TM of the amorphous silicon film 52 as the film to be crystallized in a wide region with respect to the thickness direction, and the cap film 53 functions as a heat capacitor.

On the other hand, in the case of weak irradiation (broken line B), the temperature T _Si of the amorphous silicon film 52 is not high enough to sufficiently heat the cap film 53. Only a part of the cap film 53 near the amorphous silicon layer 52 is heated so as to exceed the melting point TM. A part of the cap film 53 remains at a low temperature (melting point TM or less), and this low temperature region (cold region) acts as a heat sink.

  As a result of an experiment using a projection-type crystallization apparatus as shown in FIG. 10, the preferable thickness of the cap film 53 for increasing the lateral growth distance was in the range of 100 to 370 nm.

In FIG. 16, the horizontal axis represents the average light intensity (mJ / cm ² ), the vertical axis represents the lateral growth distance (μm) of the crystal grains, and the thickness of the cap film 53 is set to a constant value (300 nm). It is a characteristic view which shows the thermal storage effect of the cap film | membrane 53 when changing the pitch width PW of intensity distribution variously. In the figure, white circles indicate the results when the pitch width PW is 20 μm, black circles indicate the results when the pitch width PW is 28 μm, and white triangles indicate the results when the pitch width PW is 36 μm.

As is apparent from the figure, when the pitch width PW is 20 μm, the lateral growth distance increases constantly with the light intensity, and reaches a maximum of about 4 μm when the light intensity is 1000 mJ / cm ² . On the other hand, when the pitch width PW was 36 μm, the lateral growth distance remained short. In addition, when the pitch width PW was 28 μm, the lateral growth distance reached 6 μm through the light intensity that grew rapidly.

  FIG. 17A shows an SEM image of a sample in which large crystal grains are densely arranged, FIG. 17B shows an SEM image obtained by enlarging a part of the sample shown in FIG. 17B, and FIG. The light intensity distribution diagrams of the laser light irradiated on the sample are respectively shown.

  It was confirmed by this verification test that the desirable beam profile is a triangular shape with a ratio of peak intensity to valley intensity of about 2. Such a beam profile is set to be generated by a phase shifter. As shown in FIG. 17A, large crystal grains of about 5 μm were densely packed over the entire sample surface. In this way, it was possible to produce a form resembling a form in which large grains were densely packed and arranged with high reproducibility.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment. From the above, it was confirmed that it was possible to laterally grow large crystal grains (average crystal grain size of 4.0 to 6 microns) with a high filling rate using the method of the present invention.

  Next, the structure of the thin film transistor (TFT) of the present invention and the manufacturing method thereof will be described with reference to FIG. A thin film transistor was manufactured using a substrate having a semiconductor film which was crystallized by the above crystallization method.

In addition to an insulating substrate such as a glass substrate 49, a quartz substrate, or a plastic substrate, a metal substrate, a silicon substrate, or a ceramic substrate having an insulating film formed on the surface may be applied to the substrate made of an insulator or a semiconductor. Is possible. As the glass substrate 49, it is desirable to use a low alkali glass substrate, for example, represented by a # 1737 substrate manufactured by Corning. The base protective film 51 is an insulating film containing silicon oxide (SiO ₂ ) or silicon nitride as a main component, for example, a silicon oxide film having a thickness of 300 nm, and is preferably formed in close contact with the glass substrate 49. The base protective film 51 is a film that functions to prevent impurities from diffusing from the glass substrate into the non-single crystal semiconductor film.

  An amorphous semiconductor film or a non-single crystal semiconductor such as an amorphous silicon film 52 (for example, an amorphous Si film having a thickness of 200 nm formed by plasma chemical vapor deposition) is formed on the base protective film 51. .

  A cap film 53 is formed on the amorphous silicon film 52 to form the substrate 40 to be processed. The substrate to be processed 40 is subjected to a crystallization process by using a laser beam 50 that is phase-modulated by causing the pulse laser beam homogenized by the optical system shown in FIG.

  The cap film 53 on the crystallized single crystal semiconductor film is removed by etching. Next, in alignment with the crystallized region of the amorphous silicon film 52, a semiconductor circuit, for example, the thin film transistor shown in FIG. 18 is manufactured as follows. First, in order to define the shape of the active region, patterning was performed using photolithography, and Si islands having a predetermined pattern substantially corresponding to the channel region 52a, the source region 52b, and the drain region 52c were formed in the planar field of view.

Next, the gate insulating film 54 is formed over the channel region 52a, the source region 52b, and the drain region 52c. The gate insulating film 54 is a material mainly composed of silicon oxide (SiO ₂ ) or silicon oxynitride (SiON), and forms a silicon oxide film having a thickness of 30 to 120 nm. Forming the gate insulating film 54 is, for example, by plasma CVD, and the gate insulating film 54 to form a silicon oxide film using SiH ₄ and N ₂ O as raw materials to a thickness of 50nm.

  Next, a conductive layer for forming the gate electrode 55 was formed over the gate insulating layer 54. The conductive layer was formed using a material mainly composed of elements such as Ta, Ti, W, Mo, and Al by a known film formation method such as a sputtering method or a vacuum evaporation method. For example, an Al—Ti alloy was used. The gate electrode metal layer was patterned using photolithography to form a gate electrode 55 having a predetermined pattern.

Next, the source region 52b and the drain region 52c were formed by implanting impurities using the gate electrode 55 as a mask. For example, when forming a P-channel TFT, a P-type impurity such as boron ion is implanted using an ion implantation method. The boron concentration in this region was set to, for example, 1.5 × 10 ^{20 to} 3 × 10 ²¹ . In this way, high-concentration p-type impurity regions constituting the source region 52b and the drain region 52c of the P-channel TFT are formed. At this time, it goes without saying that an n-channel TFT is formed if n-type impurities are implanted.

  Next, a heat treatment step is performed to activate the impurity element implanted by the ion implantation method. This step can be performed by methods such as furnace annealing, laser annealing, and rapid thermal annealing. In the present embodiment, the activation process is performed by the furnace annealing method. The heat treatment is desirably performed in a temperature range of 300 to 650 ° C. in a nitrogen atmosphere. In this example, heat treatment was performed at 500 ° C. for 4 hours.

  Next, an interlayer insulating film 56 was formed on the gate insulating film 54 and the gate electrode 55. The interlayer insulating film 56 may be formed of a silicon nitride film, a silicon oxide film, a silicon nitride oxide film, or a laminated film that combines them. The film thickness may be 200 to 600 nm, and is 400 nm in this embodiment.

  Next, a contact hole is opened at a predetermined position in the interlayer insulating film 56. Then, a conductive layer is formed inside the contact hole and on the surface of the interlayer insulating layer 56 and patterned into a predetermined shape. In this embodiment, the source / drain electrodes 57 and 58 are formed as a laminated film having a three-layer structure in which a Ti film is 100 nm, an aluminum film containing Ti is 300 nm, and a Ti film is 150 nm continuously formed by sputtering. Thus, the thin film transistor shown in FIG. 18 was obtained.

  Hereinafter, an example in which the thin film transistor obtained in the above-described embodiment is actually applied to an active matrix liquid crystal display device will be described. FIG. 19 is a diagram illustrating an example of an active matrix display device using a thin film transistor. The display device 70 has a panel structure including a pair of insulating substrates 71 and 72 and an electro-optical material 73 held between the substrates. A liquid crystal material is widely used as the electro-optical material 73. A pixel array unit 74 and a drive circuit unit are integrated on the lower insulating substrate 71. The drive circuit section is divided into a vertical drive circuit 75 and a horizontal drive circuit 76.

  Further, a terminal portion 77 for external connection is formed at the upper end of the peripheral portion of the insulating substrate 71. The terminal portion 77 is connected to the vertical drive circuit 75 and the horizontal drive circuit 76 via the wiring 78. In the pixel array portion 74, row-shaped gate wirings 79 and column-shaped signal wirings 80 are formed. A pixel electrode 81 and a thin film transistor 82 for driving the pixel electrode 81 are formed at the intersection of both wirings. The gate electrode of the thin film transistor 82 is connected to the corresponding gate wiring 79, the drain region is connected to the corresponding pixel electrode 81, and the source region is connected to the corresponding signal wiring 80. The gate wiring 79 is connected to the vertical driving circuit 75, while the signal wiring 80 is connected to the horizontal driving circuit 76.

  The thin film transistor 82 for switching and driving the pixel electrode 81 and the thin film transistor included in the vertical drive circuit 75 and the horizontal drive circuit 76 are manufactured according to the present invention and have higher mobility than the conventional one. Therefore, not only the drive circuit but also a higher-performance processing circuit can be integrated.

  As described above, according to the above embodiment, crystallization with a large particle size can be performed even at a low temperature, for example, room temperature or a temperature range in the vicinity thereof (for example, 5 to 50 ° C.) during the crystallization process. Since the non-single crystal semiconductor film is irradiated with phase-modulated light, higher-order vibration components are reduced.

  The present invention can be applied not only to a liquid crystal display device but also to an organic electroluminescence display device and an electronic circuit device.

(A) is a diagram showing the phase shifter and the substrate, (b) is a diagram showing the light intensity distribution of the homogenized laser beam that has passed through the phase shifter, and (c) is a diagram showing the light intensity distribution of the laser beam in three dimensions. . (A) is a figure which shows typically the light intensity distribution of the laser beam phase-modulated before the board | substrate incidence, (b) is a scanning electron microscope which shows the sample crystallized by single shot irradiation of the pulsed laser beam ( SEM) image. 1 is a configuration block diagram showing an outline of a crystallization apparatus of the present invention. The internal see-through block diagram showing the optical system of the device of the present invention. FIG. 9 is a schematic cross-sectional view illustrating a manufacturing process of a thin film transistor of the present invention. The SEM image which shows the effect of this invention. The characteristic view which shows the effect of this invention. The characteristic view which shows the effect of this invention. The characteristic view which shows the effect of this invention. The block diagram for demonstrating other embodiment of FIG. The characteristic view which shows the effect of this invention. The characteristic view which shows the effect of this invention. The characteristic view which shows the effect of this invention. (A) is the SEM image of the sample after Secco etching, (b) is a light intensity distribution map, (c) is the SEM image of the sample after Secco etching. The schematic diagram explaining the effect of this invention. The characteristic view which shows the effect of this invention. (A) is an SEM image of a sample in which large crystal grains are densely arranged, (b) is an enlarged SEM image of a part of the sample shown in (a), and (c) is a laser irradiated to the sample shown in (b). The light intensity distribution map of light. 1 is a schematic cross-sectional view showing a thin film transistor according to an embodiment of the present invention. The perspective view which shows the outline | summary of the display apparatus which concerns on embodiment of this invention. The block diagram which shows the outline | summary of a conventional apparatus. (A) is a figure which shows a phase shifter and a board | substrate, (b) is a figure which shows light intensity distribution after a parallel pulse laser beam passes a phase shifter. The characteristic view which shows the relationship between the film thickness (nm) of an amorphous silicon film, and the lateral growth distance (micrometer) of a crystal grain. The characteristic view which shows the relationship between the film thickness (nm) of an amorphous silicon film, and the film thickness (nm) of a cap film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Excimer laser apparatus, 2a, 2b ... Optical lens,
3 ... Homogenizer (lighting system) 33, 35 ... Fly eye lens,
34, 36 ... condenser optical system,
4 ... Phase shifter (spatial intensity modulation optical element),
5, 40 ... Substrate to be processed, 43 ... Imaging optical system, 48 ... Silicon substrate,
49 ... Glass substrate, 50 ... Laser beam, 51 ... Underlying protective film (first insulating layer),
52 ... Amorphous silicon film (non-single crystal semiconductor film, a-Si film),
52a ... channel region, 52b ... source region, 52c ... drain region,
53. Cap film (SiO ₂ film; second insulating layer),
54 ... Gate insulating film, 55 ... Gate electrode, 56 ... Interlayer insulating film,
57 ... Source electrode, 58 ... Drain electrode,
6: mounting table, 7 ... X, Y, Z, θ stage.

Claims (4)

A laser device in which the timing of oscillating the laser beam is controlled, a homogenizer arranged on the same optical axis as the laser beam oscillated from the laser device, and the same intensity as the homogenizer A spatial intensity modulation optical element disposed on the optical axis, a mounting table for mounting a substrate to be processed provided in the optical path of the laser beam, a substrate to be processed on the mounting table, and the spatial intensity modulation optics A crystallization method for crystallization by irradiating a non-single crystal semiconductor film provided on the substrate to be processed with a laser beam using a projection type crystallization apparatus having an imaging optical system disposed between the elements Because
A cap film is provided on the laser light incident surface of the non-single crystal semiconductor film,
By irradiating the non-single crystal semiconductor film through this cap film with a laser beam having a light intensity distribution having an inverted triangular peak pattern that repeats monotonous increase and decrease, only the irradiated part is melted and temperature drop is started. After that, the solidification of the reverse peak point that becomes the minimum of the irradiation part starts, and the solidification point moves according to the gradient of the cross-section inverted triangular peak pattern, and the crystal grows in the lateral direction,
The irradiation position by the laser beam from the mounting table and the laser device is relatively moved to crystallize a predetermined region of the non-single crystal semiconductor film, thereby minimizing the laser beam irradiation portion. A crystallization method comprising crystallization from an inverse peak point . The crystallization method according to claim 1 , wherein the cap film has a thickness of 80 nm to 400 nm . 3. The crystallization method according to claim 1 , wherein the laser light is light that is made uniform with respect to an incident angle and a light intensity. The crystallization method according to claim 1, wherein the cap film has a thickness of 130 nm to 400 nm.

Images