JP2005064078A - Method and device for crystallizing semiconductor thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for crystallizing semiconductor thin film for which problems of the conventional technology has been solved. <P>SOLUTION: Incident laser light is modulated into a laser light, having a light intensity distribution having extremely low light intensity lines extended in one direction by means of a first phase shifter 126a and at the same time, into another laser light having a light intensity distribution containing extremely small light intensity lines extended in a direction intersecting the direction mentioned by means of a second phase shifter 127a, arranged at a position which is different from the position of the first phase shifter 126a in the same optical path. Then the crystal grains, corresponding to the minimum light intensity points, are grown in the lateral direction from crystallization starting points, by having a laser light emitted having a light intensity distribution containing minimum light intensity points composed of the intersections of the two kinds of extremely small light intensity lines, and irradiating a thin non-single-crystal semiconductor film with the emitted laser light, from one surface side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for crystallizing a semiconductor thin film and a method for manufacturing a semiconductor device.
[0002]
In general, even in a single crystal, disorder of atomic columns (dislocations, etc.) exists, and it is difficult to distinguish between “single crystal” and “crystal close to a single crystal”. “Crystal close to crystal” is also described as “single crystal”.
[0003]
[Prior art]
SOI (Silicon On Insulator) technology for forming single crystal silicon on an insulating material substrate or an insulating film is known as a technology for realizing high integration, low power consumption and high speed of LSI (Ultra large-Scale Integrated circuit). It has been. The process of this technique includes (1) a method of forming an insulating film in a lower surface region of a single crystal semiconductor wafer, for example, a silicon wafer, and (2) an amorphous material or a multi-layer formed on an insulating material substrate or an insulating film. A method of crystallizing or recrystallizing a crystalline semiconductor thin film, for example, a single crystal silicon or polycrystalline silicon thin film. In any of the methods, it is extremely important to improve the crystallinity of silicon. The region in which the transistor is formed is a single crystal, and the crystal plane orientation is uniform, in particular, the surface is the (001) plane and the current. It is desirable that the crystal orientation of the flowing direction is (100) plane. For this reason, the method (1) such as SIMOX using a single crystal silicon wafer or a bonded substrate has been put into practical use.
[0004]
On the other hand, method (2) is not adopted in today's silicon ULSI technology, but it can be applied to various electronic elements and electronic devices if it can form high-quality semiconductor thin films such as silicon without any limitation on the substrate material. is there. For this reason, improvement of the method (2) is strongly desired.
[0005]
In the 1980s, many studies were conducted with the aim of forming single crystal silicon thin films with uniform plane orientation. Among them, the zone melting method using high frequency induction heating is an important technique and is known as a technique capable of forming a single crystal silicon rectangular region having a (001) plane of crystal orientation on the surface. This method will be described below with reference to FIG. Details are described in “Akira Fukami, Hiroshi Kobayashi, Electronic Communication Society Journal 1986/9 vol. J69-C No. 9 p. 1089-1095” (Non-patent Document 1).
[0006]
First, as shown in the drawing, a polycrystalline Si thin film is deposited on a quartz substrate 11 by using an atmospheric pressure chemical vapor deposition method, and this thin film becomes two rectangular regions 14 connected to each other by a neck portion 14a. To pattern. Next, the elongated high-frequency induction heater 17 is positioned below the quartz substrate 11 and heated in a band shape to 1412 ° C. or more, and the polycrystalline silicon at a location corresponding to the heater 17 is melted to melt the band-shaped silicon. Region 13 is formed. Next, by moving the heater 17 linearly in the direction indicated by the arrow 15, the single crystal silicon is sequentially melted to melt the entire rectangular region 14 to be single crystallized. FIG. 1 shows a state in which the heater 13 is in the middle of movement. Of the rectangular region 14, the portion indicated by reference numeral 12 has already been crystallized, and the blank portion has not been crystallized. Here, when the dimensions of the neck portion 14a (length L and width W in the figure) are changed, the heat flow changes locally, and the crystal orientation changes depending on the heat flow. When L and W are optimized, a crystallized rectangular region 12 having a (001) plane orientation can be formed.
By the way, a technique for forming a crystallized silicon thin film on a glass or plastic substrate is applied to a technique for improving the performance of a thin film transistor used for a driving element such as a liquid crystal display. For example, when the semiconductor layer of a thin film transistor is changed from an amorphous structure to a polycrystalline structure, the mobility of the transistor becomes 100 times or more. However, in this case, attention must be paid to thermal damage in the substrate for crystallization (for example, it must be 600 ° C. or lower for a general glass substrate and 150 ° C. or lower for a plastic). The zone melting method using high frequency induction heating raises the temperature of the substrate (quartz substrate), and therefore cannot be applied to the field of liquid crystal displays in which the substrate is formed of the above materials.
[0007]
For this purpose, an excimer laser crystallization method has been developed as a method for crystallizing an amorphous silicon thin film without causing thermal damage to the substrate. In this technique, as shown in FIG. 2, the intensity of the light irradiation cross section of the excimer laser beam 21 is made uniform by a homogenizing optical system 22 and shaped into a rectangular shape through a metal mask 23 having an elongated rectangular opening (for example, the cross sectional shape is (150 mm × 200 μm). With this emitted laser light, the surface of the amorphous silicon thin film 24 deposited on the glass substrate 26 is linearly scanned in the direction indicated by the arrow 27, and laser irradiation is performed at intervals of 10 μm in the minor axis direction. ing. The silicon thin film that has absorbed the laser light is converted into polycrystalline silicon 28 after passing through molten silicon 25. With this technology, even if a general glass or plastic substrate is used, the substrate is not thermally damaged. This is because the excimer laser is a pulse laser of about 20 ns, and crystallization is completed in about 50 to 100 ns. The crystal grain size depends on the laser energy density, and a polycrystalline thin film having a grain size of about 0.1 to 1 μm can be formed. Regarding the plane orientation, the crystal grains formed by one laser irradiation are not oriented, but the surface orientation is oriented to the (001) plane or the (111) plane by performing laser irradiation several times about several hundred times. There is a report to do. The former is, for example, D.I. P. Gosain, A.M. Macida, T .; Fujino, Y. et al. Hitsuda, K.K. Nakano and J.M. Sato, “Formation of (100)-Textured Si Film Using an Excimer Laser on a Glass Substrate”, Jpn. J. et al. Appl. Phys. Vol. 42 (2003) p. L135-L. 137. (Non-patent Document 2). The latter is described in, for example, H.P. Kuriyama, et al. , “Enlargement of Poly-Si Film Grain Size by Excimer Laser Annealing and Its Application to High-Performance Poly-Si Thin Transist.” J. et al. Appl. Phys. Vol. 30 (1991) p. 3700-3703 (Non-patent Document 3).
[0008]
Further, as a technique developed from the excimer laser annealing, a technique called SLS (Sequential Lateral Solidification) is known. Such a technique is disclosed in Japanese Patent No. 3204986 (Patent Document 1). In this technique, as shown in FIG. 3A, an excimer laser beam 31 whose light intensity has been made uniform by a homogenizing optical system is passed through a mask 32 provided with a metal slit having a width of about 2 microns. To shape. When the fluence (energy density) of the laser passing through the slit is set so that the amorphous silicon thin film 33 is fully melted 34 in the thickness direction, it grows laterally inward from the outer region of the slit. And crystallized silicon 36 is formed (FIG. 3B). Next, when the sample is moved to the left by 2 microns as shown by an arrow 37 and laser irradiation is performed, the molten silicon 34 grows laterally using the right end portion of the crystallized silicon 36 formed by the pre-irradiation as a seed crystal (FIG. 2). (C)). By repeating this laser irradiation and sample movement process, a polycrystalline silicon thin film having a large grain size can be formed. In this case, if the planar shape of the mask 32 is changed to the checkered mask 39 as shown in FIG. 2D and the laser irradiation is repeated, the processing time is improved and the overlapping region of crystallization is improved, and the substrate surface is improved. A uniform laterally formed polycrystalline thin film can be formed.
[0009]
As a further developed method of the excimer laser crystallization method, a phase modulation excimer laser crystallization method is known. The feature of this method is that, as shown in FIG. 4A, an excimer laser beam 41 is passed through an optical component called a phase shifter 42 (for example, a step processed on a quartz plate), thereby FIG. The laser light intensity distribution is modulated as indicated by reference numeral 43. The amorphous silicon thin film 44 is irradiated once with the laser beam modulated in this way, and the irradiated region 45 is crystallized as shown in FIG.
[0010]
Unlike the excimer laser crystallization method and the SLS method, this method does not use a uniform light intensity distribution and does not require multiple laser irradiations. In this method, an inclined temperature distribution is generated in the laser-irradiated thin film due to the modulated light intensity distribution 43, and crystal nuclei are formed in a portion 47 having a small energy, and this position can be accurately determined. Further, as shown in FIG. 4 (d), the growth distance is increased by lateral growth based on the crystal nuclei, and large grain crystal grains 46a and 46b can be obtained. By this method, large crystal grains are formed, and the position of the crystal grains can be controlled. Details of this technique are described in “Masayoshi Matsumura, Surface Science Vol. 21, No. 5, pp. 278-287, 2000” (Non-patent Document 4).
[0011]
[Patent Document 1]
Japanese Patent Application No. 9-542270
[0012]
[Non-Patent Document 1]
IEICE Transactions 1986/9 vol. J69-C No. 9 p. 1089-1095
[0013]
[Non-Patent Document 2]
Jpn. J. et al. Appl. Phys. Vol. 42 (2003) p. L135-L. 137
[0014]
[Non-Patent Document 3]
Jpn. J. et al. Appl. Phys. Vol. 30 (1991) p. 3700-3703
[0015]
[Non-Patent Document 4]
Surface Science Vol. 21, no. 5, pp. 278-287, 2000
[0016]
[Problems to be solved by the invention]
However, in the technique of forming a single crystal region with a uniform plane orientation on an insulating layer without selecting a substrate material, the above four types of conventional techniques have the following problems.
[0017]
In the zone melting method using high-frequency induction heating described with reference to FIG. 1, the substrate is partially heated to a melting point of silicon (1410 ° C.) or higher so that a substrate made of a low melting point material such as glass is used. It cannot be used for the intended use.
[0018]
In order to orient the crystallized film in the (001) plane orientation, it is necessary to optimize the shape of the island-like silicon connecting portion (neck portion), which limits the layout of transistors and circuits to be formed later.
[0019]
With respect to the excimer laser crystallization method described with reference to FIG. 2, the crystallinity inside the crystal grains can be a single crystal. However, when a large number of transistors are formed, there is a grain boundary in the channel region, so that movement occurs. As a result, the performance (threshold voltage, sub-shred coefficient, mobility) varies among transistors. In addition, in order to enlarge the crystal grains, it is necessary to bring them close to the critical laser fluence where the silicon thin film is completely melted. However, when the laser fluence exceeds the total melting condition, the silicon thin film is microcrystallized, which is not preferable. That is, the tolerance for laser fluence is narrow. In addition, since the crystal grain size is about 1 to 2 microns at the maximum, there is a restriction that the transistor size must be reduced. For this reason, for example, when a large-area substrate for display having a dimension of about 1 mx1 m is used, an extremely advanced fine processing technique is required. Further, in order to set the surface orientation to (001), the laser must be irradiated 200 times or more (about 10 times to make the (111) plane). For this reason, the processing time of crystallization becomes long. In addition, although the orientation of the surface of each crystal grain that becomes the upper surface (one surface) of the crystallized film can be made constant (001), it is in a positional relationship that rotates randomly with respect to the surface axis. The crystal orientation of the cross section is not oriented. That is, the plane perpendicular to the surface of the crystallized film cannot be the (001) orientation.
[0020]
With the SLS method described with reference to FIG. 3, nearly half of the laser beam is shielded with a metal mask, so that the laser energy cannot be used effectively. For this reason, the processing time of crystallization becomes long. Further, since the positions of the crystal grains vary, the performance variation between the transistors occurs as in the case of the excimer laser crystallization. And, since the plane orientation of the crystal grains is not constant, the performance varies between transistors.
[0021]
Regarding the phase modulation excimer laser crystallization technology described with reference to FIG.
Since the surface shape of the crystal grains is mainly triangular, there is a limitation on the circuit layout when forming the transistor circuit. In addition, since the plane orientation of the crystal grains is not constant, the performance varies among transistors.
[0022]
The present invention has been made based on the above problems, and an object thereof is to provide a semiconductor thin film crystallization method and a crystallization apparatus in which crystal grains in a desired plane direction are formed in a semiconductor thin film.
[0023]
[Means for Solving the Problems]
Thus, in the method for crystallizing a semiconductor thin film according to one embodiment of the present invention, the incident laser light is modulated by the first optical modulation element into laser light having a light intensity distribution having a minimum light intensity line extending in one direction. In addition, the laser light having the light intensity distribution having the minimum light intensity line extending in the direction intersecting the one direction of the incident laser light is secondly arranged at a position different from the first optical modulation element on the optical path. A step of emitting a laser beam having a light intensity distribution having a minimum light intensity point where these minimum light intensity lines intersect,
A first laser irradiation step of irradiating a non-single-crystal semiconductor thin film from one side with the emitted laser light and growing crystal grains corresponding to the minimum light intensity point in a lateral direction from a crystal start point; It is characterized by that.
[0024]
A crystallization apparatus according to another aspect of the present invention includes an emission unit that emits laser light having a uniform light intensity distribution, and
A supporting means for supporting the non-single-crystal semiconductor thin film;
Light intensities arranged at different positions on the optical path between the emission means and the support means and having first and second minimum light intensity lines by modulating the phase of the laser light emitted from the emission means. First and second optical modulation elements for emitting laser beams of distribution, respectively,
The first optical modulation element and the second optical modulation element have a light intensity distribution in which the first minimum light intensity line and the second minimum light intensity line intersect to have a minimum light intensity point. The modulated laser beam is irradiated on the semiconductor thin film from one side so that crystal grains corresponding to the minimum light intensity point grow laterally from the crystal growth point to the semiconductor thin film. It is characterized by that.
[0025]
According to the method and apparatus of the above aspect, the amorphous or polycrystalline semiconductor thin film can be a crystallized semiconductor thin film whose crystal orientation is defined with respect to the substrate.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
The basic concept of the present invention will be described below.
[0027]
As shown in FIG. 14A, the inventors of the present application use a phase shifter 141 in which a linear step is processed on the surface of a quartz substrate as an optical modulation element, and the laser light from the light source is shown in FIG. It was modulated into a laser light intensity distribution 51 as shown, and irradiated to an uncrystallized thin film (in this case, an amorphous silicon thin film) to crystallize (in this case, other crystalline silicon). Then, the surface morphology of the crystallized crystal grains and the crystallographic orientation of each crystal grain were measured using a scanning electron microscope (SEM) method and an electron backscattering (EBSP) method. As a result, it was found that the form of crystal grains can be classified into three types, that is, small crystal grains 52, strip-shaped crystal grains 53, and Δ-shaped crystal grains 54 as shown in FIG. When these three kinds of crystal grains are schematized and a known plane orientation relationship is added, the result is as shown in FIG. In FIG. 5C, the crystal grains corresponding to the small grain crystal grains 52, the strip-shaped crystal grains 53, and the Δ-shaped crystal grains 54 are given the same reference numerals with suffix “a”. Here, the inventors of the present invention noted that the growth distance of the Δ-shaped crystal grains 54a is long, the plane orientation in the crystal growth direction is the (100) plane, and two perpendicular directions with respect to the crystal growth direction. Of these, the vertical direction in the plane of the thin film is the (010) plane or the (011) plane. Therefore, the present inventors performed the first phase-modulated excimer laser irradiation so that the linear region 61a has the minimum laser light intensity as shown in FIG. 6A (irradiation with the minimum light intensity line). If the bottom region 61b of the Δ-shaped crystal grain 64 formed thereby is used as a seed crystal, that is, a crystal nucleus (crystal growth origin, crystal growth region), and the second phase modulation excimer laser irradiation is performed, the plane orientation is aligned. In addition, the present inventors have found that the crystal grains have a square shape 64. That is, as shown in FIG. 6B, it was found that the second phase modulation excimer laser irradiation should be such that the linear region 61b has a minimum intensity (irradiation with a minimum light intensity line). By the second phase modulation excimer laser irradiation, the left and right regions of the region 61b are completely melted, so that crystal growth occurs in the left and right directions of the region 61b. As a result, as shown in FIG. 6C, at least the plane orientation in the crystal growth direction has a (001) plane, and quadrangular crystal grains are formed. FIG. 6 shows the crystallized film as viewed from above. Further, by using the phase shifter 141 shown in FIG. 14A, the pitch P in the horizontal direction (left-right direction) is constant, for example, a plurality of minimum light intensity points (reverse peak points) 62a of 10 μm are shown in FIG. The amorphous film 80 is irradiated with the first phase-modulated excimer laser with the laser beam having the laser beam intensity distribution 81 shown in a), and then the phase shifter 141 and the amorphous film 80 are approximately 2 / P (approximately 5 μm). If the second phase-modulated excimer laser irradiation is performed with a relative shift, crystal grains whose position is controlled two-dimensionally can be formed as shown in FIG. Here, the pitch P is a step between the elongated groove formed on the surface and the surface so as to shift the phase of the incident laser light by 180 ° (π), as will be described later with reference to FIG. That is, the interval between the phase shift lines.
[0028]
The following conclusions were drawn from the above experiments and measurements.
[0029]
In order to manufacture a crystallized film in which a crystal grain having a rectangular surface shape is one-dimensionally controlled and at least the plane orientation in the growth direction is (001), a one-dimensional as shown in FIG. A phase shifter 141 is used to form a one-dimensional laser light intensity distribution, and the amorphous silicon thin film surface is irradiated with laser to form crystal grains grown in one direction (first laser irradiation). At this time, as shown in FIG. 5A, the laser light to be irradiated is designed so that the start position and the end position of crystal growth become the minimum value J1 and the maximum value J2 of the laser light intensity. By such cyclic annealing by the first laser irradiation, the entire region irradiated with the amorphous silicon thin film is filled with laterally grown crystal grains. Next, as shown in the scanning electron micrograph of FIG. 7A, the second laser irradiation is performed so that the laser intensity maximum region (the bottom region of the Δ-shaped crystal grains) 72 in the first laser irradiation becomes a minimum region. (Irradiation with the minimum light intensity line). At this time, the small crystal grains 75 and the strip-shaped crystal grains 73 are completely melted, and the base region 72 of the Δ-shaped crystal grains becomes a seed crystal, and melted and recrystallized in the horizontal direction of the region 72. A scanning electron micrograph of the surface of the crystallized thin film after the second laser irradiation is shown in FIG. In the second laser irradiation, the bottom region of the triangular crystal grain whose growth direction in the first laser irradiation is the (001) plane becomes a seed crystal, and the small grain crystal grain formed by the first laser irradiation, It shows that the strip-shaped crystal grains are remelted and taken into crystal growth from the seed crystal. Therefore, by the second laser irradiation, crystal grains 74b whose growth direction is the (001) plane and whose surface form is a square shape are formed. This was confirmed by electron backscattering.
[0030]
Further developing the above technical idea, as shown in FIG. 14C, the phase shifter 141, that is, the phase shift line, that is, the phase shift line orthogonal to each other, and the phase shifter 142 shown in FIG. Are combined to form a light intensity distribution 81 as shown in FIG. The light intensity distribution shown in this figure has three minimum light intensity lines and nine minimum light intensity points, but these numbers are arbitrary in the present invention. This light intensity distribution 81 is characterized in that a minimum point exists in the minimum intensity region (line). By controlling the crystal growth start point 82 two-dimensionally, the arrangement of the pentagonal crystal grains 83 is controlled. Can be formed. Further, the minimum light intensity line formed corresponding to the phase shift line of the first phase shifter and the minimum light intensity line formed corresponding to the phase shift line of the second phase shifter should intersect each other. For example, it does not necessarily have to be orthogonal. In FIG. 8 (b) showing a scanning electron micrograph of the surface morphology of a silicon thin film crystallized using the light intensity distribution 81 as described above, the crystal growth start point corresponding to the crystal growth start point 82 is indicated by 82a. The single crystallization region is indicated by 83a. By combining this technical idea with the secondary recrystallization method, single crystal regions with controlled growth orientations can be arranged two-dimensionally.
[0031]
Further, when the above technical idea is developed, a semiconductor thin film substrate having a crystal plane orientation can be produced by indicating the orientation to a substrate to be used in advance, and forming a light intensity distribution in accordance with the orientation to perform crystallization. When a substantially circular semiconductor substrate is used, as shown in FIG. 9A, orientation indication indicators such as orientation flat 91, notch 92, substrate marking 93, etc. are formed in advance on the substrate (semiconductor wafer), and this indicator is used as a reference. Thus, the laser light intensity distribution direction (intensity gradient direction) is matched. In the case of a rectangular substrate such as a glass substrate, as shown in FIG. 9B, orientation indication indicators such as one side 94, corner cut 95, and substrate marking 96 are formed in advance, and this indicator is used as a reference. Thus, the laser light intensity distribution direction (intensity gradient direction) is matched. Thus, by performing crystallization, a crystallized semiconductor thin film substrate in which the crystal plane orientation of the cross section of the thin film is known can be obtained from the substrate.
[0032]
Embodiments based on the above basic concept will be described below with reference to the accompanying drawings.
[0033]
First Embodiment A surface on a semiconductor substrate (indicated by reference numeral 101 in FIG. 10) having an orientation display index such as an orientation flat 91, a notch 92, a substrate mark 93 and the like as shown in FIG. FIG. 5, FIG. 6, FIG. 7, FIG. 8, FIG. 9, FIG. 10 show embodiments of a semiconductor device having a rectangular crystallized region array with uniform orientation, a method for manufacturing the same, and a method for crystallizing a semiconductor thin film. In particular, it will be described with reference mainly to FIG.
[0034]
First, the semiconductor substrate 101 _{(e.g., Si, Ge, Si 1-} x Ge x, Si 1-x-y Ge x C y, GaAs, GaP, InAs, GaN, ZnTe, CdSe, semiconductor wafers, such as CdTe) a prepare. An insulating layer 102 (for example, a film thickness of 500 nm) is formed on the semiconductor substrate 101. The insulating layer 102 is, for example, a SiO ₂ film formed by thermal oxidation, CVD (for example, plasma chemical vapor deposition or low pressure chemical vapor deposition) or sputtering. Instead, the insulating layer 102 may have a laminated structure such as a combination of a SiN film and a SiO ₂ film. The insulating layer 102 may be formed over the entire surface of the semiconductor substrate 101 and left as it is or may be left partially by patterning. Here, a case where the semiconductor substrate 101 is provided over the entire surface will be described. Next, an amorphous or polycrystalline semiconductor thin film 103 (for example, Si, Si _1-x Ge _{x having} a film thickness of about 30 to 200 nm is formed on the insulating layer 102, that is, on one surface side of the semiconductor substrate 101. , Or Si _1-xy Ge _{x Cy} film) is formed using CVD (for example, plasma chemical vapor deposition or low pressure chemical vapor deposition) or sputtering. The semiconductor thin film 103 may be formed on the entire surface of the insulating layer 102 or on a partial region of the insulating layer by patterning. Here, it is formed on the entire surface of the insulating film 102.
[0035]
Then, as shown in FIG. 10A, a protective film 104 (for example, SiO ₂ , SiON, SiN, or a laminated structure film thereof) is formed on the entire surface of the semiconductor thin film 103 with a film thickness of about 300 nm. Form a film. When the insulating layer 102 and the semiconductor thin film 103 are patterned, a protective film may be formed on the entire surface of the substrate.
[0036]
Next, as shown in FIG. 10B, the surface of the protective film 104 is irradiated with an excimer laser beam 105 having a light intensity distribution as shown in FIG. 8A by using a phase modulation excimer laser crystallization method. To do. This laser irradiation is called first laser irradiation. Here, the phase modulation excimer laser crystallization method uses the laser crystallization apparatus described in the third embodiment. For such laser light irradiation, the irradiation position can be set in accordance with an alignment mark provided in advance on the substrate or semiconductor wafer.
[0037]
Although the first laser irradiation uses a light intensity distribution having a plurality of reverse peaks, the case of three reverse peaks is shown in the figure for simplicity. This light intensity distribution includes a pair of main gradient directions (light intensity directions in which the light intensity increases almost linearly from the minimum light intensity point) 106 and / or around each reverse peak point (minimum light intensity point). 106a exists. The pair of main gradient directions 106 and 106a are in a 180 ° rotation relationship with each other in the drawing. The semiconductor substrate 101 and the phase shifter are set in advance so that the main gradient direction 106 or 106a and the direction of the orientation display index of the semiconductor substrate 101 have a predetermined relationship. Here, the main gradient direction 106 and the orientation flat 91 are set to be parallel.
[0038]
In this first laser irradiation, as shown in FIG. 5A, the energy density of the laser beam is such that the minimum value of the light intensity exceeds the critical value j1 of the lateral growth condition, and the maximum value of the light intensity is It is desirable that the vaporization critical value j2 or less of the semiconductor thin film 103 is not greater. The values of these critical values j1 and J2 are mainly determined by the absorption coefficient and film thickness of the semiconductor thin film 103 with respect to the laser beam.
[0039]
By irradiation of the first laser beam 105 with the first laser beam 105, the irradiated region of the semiconductor thin film 103 is crystallized and converted into the polycrystalline semiconductor thin film 107. The surface form of the crystallized thin film 107 is crystallized in the lateral direction along the main gradient directions 106 and 106a. At this stage, when the protective film is removed by etching and analyzed by scanning electron microscopy and electron backscattering, each crystal grain starts crystal growth from a position where the laser light intensity is low, and the direction of the main gradient 106, 106a is reached. It can be seen that the crystal has grown along. Each crystal grain is presumed to have grown from one crystal nucleus, and as classified in FIG. 5C, small grain crystal grains 52a, strip-shaped crystal grains 53a, and Δ-shaped crystal grains 54a. And are formed. Among them, the Δ-shaped crystal grain 54a has the longest lateral growth distance. When the crystal orientation of each crystal grain is analyzed by the electron beam backscattering method, the plane orientation of the growth direction (that is, main gradient 106, 106a) of the Δ-shaped crystal grain 54a is (100). The growth distance of the Δ-shaped crystal grains 54a is at least 2 mm or more, and is 5 mm in this embodiment. On the other hand, the crystal plane orientation in the main gradient direction of the small grain crystal grains 52a and the strip-shaped crystal grains 53a is the (111) or (110) plane.
[0040]
Next, as shown in FIG. 10C, second laser irradiation is performed on the polycrystalline region using the second laser beam 108. The light intensity distribution of the second laser irradiation can be understood by comparing FIGS. 10B and 10C, where the position of the minimum value of the light intensity used in the first laser irradiation is the second. The light intensity distribution of the first laser irradiation is set so as to be a light intensity distribution translated by about ½ of the minimum value pitch. That is, the region 61 (a) shown in FIG. 6A is the minimum value of the first laser irradiation, and the region 61 (b) is the minimum value of the second laser irradiation. Here, if the light intensity distribution is such that the intensity further decreases to the position of the minimum light intensity point 62a as shown in the laser light intensity distribution 81 shown in FIG. Can be controlled to dimensions. In the present embodiment, as described above, a light intensity distribution that is translated in the main gradient direction by ½P (5 mm) is used. FIG. 7A shows the result of observing the surface morphology of the crystallized silicon thin film after the first laser irradiation with a scanning electron microscope. In this figure, reference numeral 71 indicates a region where the light intensity of the first laser irradiation is minimal, and reference symbol 72 indicates a maximum region. Also in this photograph, as shown in FIG. 5B, it can be seen that small grain crystal grains 75, strip-shaped crystal grains 73, and Δ-shaped crystal grains 74a are formed. The second laser irradiation is performed so that the light intensity is minimized in the region indicated by reference numeral 72. The energy density of the second laser irradiation is set to be equal to or greater than the energy density of the first laser irradiation. In this embodiment, the second laser irradiation is performed by using the light intensity distribution of the first laser irradiation and translating the sample surface by 5 mm in the main gradient direction. It is not always necessary to use the same phase shifter, and another phase shifter whose phase is shifted by 1 / 2P may be used.
[0041]
By the second laser irradiation, the polycrystalline semiconductor region 107 is converted into a semiconductor region 109 having large crystal grains as shown in FIG. The point where the light intensity at this time is the minimum is indicated by reference numeral 72 in FIG. In this figure, it is shown that the second laser irradiation crystallizes in the lateral direction to the left and right of the region 72. Further, in this drawing, crystal grains 74b corresponding to the crystal grains of the semiconductor region 109 shown in FIG. The surface shape of the crystal grain 74b (the shape when the semiconductor region 109 is viewed from above, that is, the shape in the horizontal plane) is substantially square (rectangular), and the main gradient directions 106 and 106a of the light intensity distribution The plane orientation of the crystal grains is (100). Note that the crystallinity of the crystallized region of the semiconductor region 109 is a single crystal. In FIG. 7B, as described above, there are almost no small crystal grains, strip crystal grains, or triangular crystal grains observed in FIG. This is because the bottom part of the Δ-shaped grains 74a formed by the first laser irradiation is not completely melted by the second laser irradiation, while the small grain crystal grains 75 and the strip crystal grains 73 are It is because it completely remelts. For this reason, crystal growth occurs in the direction of the main gradient direction 106 (or 106a) using the region 72 where the light intensity is minimum as a seed crystal. The small crystal grains 75 and the strip-shaped crystal grains 73 having the (111) plane or the (110) plane in the main gradient direction disappear and are oriented in the (100) plane in the main gradient direction 106 (or 106a) direction. It has been converted to crystal grains.
[0042]
As can be seen from the above description, the plane orientation of the crystal grains of the semiconductor region 109 formed by the method of this embodiment along the orientation flat of the semiconductor substrate 101 is the (100) plane.
[0043]
Therefore, according to the method of the present embodiment, a single crystallized region array having a (100) plane orientation in one direction of the cross section and composed of substantially rectangular crystal grains can be formed on the semiconductor substrate. . In the method described above, it seems that a part of the semiconductor thin film 103 is single-crystallized in the drawing, but the entire semiconductor thin film 103 can be single-crystallized by repeating the above process.
[0044]
Second Embodiment FIGS. 9 and 11 show an embodiment relating to a semiconductor device having a rectangular crystallized region array with a uniform plane orientation on an insulating material substrate, a method for manufacturing the same, and a method for crystallizing a semiconductor thin film. The description will be given with reference.
[0045]
First, an insulating material substrate 111 (for example, quartz glass, soda glass, borosilicate glass, lead glass) having sides 94, notches 95, or markings 96 (which may be the front surface or the back surface of the substrate) as shown in FIG. 9B. , Fluoride glass, sapphire, plastic, polyimide, etc.) are prepared (FIG. 11A). An insulating layer 112 (for example, a film thickness of 500 nm) is formed over the insulating material substrate 111. The insulating layer 112 is a SiO ₂ thin film formed using, for example, CVD (for example, plasma chemical vapor deposition or low pressure chemical vapor deposition) or sputtering. Instead, the insulating layer 112 may have a laminated structure made of different materials such as SiN and SiO ₂ . The insulating layer 112 may be formed on the entire surface of the insulating material substrate 111 or on a partial region on the surface of the insulating material substrate by patterning. Here, the insulating material substrate 111 is formed on the entire surface. Next, an amorphous or polycrystalline semiconductor thin film 113 (for example, Si, Ge, Si _1-x Ge _x , Si _1-xy Ge _{x having} a thickness of about 30 to 200 nm is formed on the insulating layer 112. _Cy or the like) is formed using a CVD method (for example, a plasma chemical vapor deposition method or a low pressure chemical vapor deposition method) or a sputtering method. The semiconductor thin film 113 may be formed on the entire surface of the insulating layer 112 or on a partial region of the insulating layer by patterning. Here, the insulating layer 112 is formed on the entire surface.
[0046]
Then, as shown in FIG. 11A, a protective film 114 (for example, SiO ₂ , SiON, SiN, or a laminated structure film thereof) is formed to a thickness of about 300 nm on the entire surface of the semiconductor thin film 113. . When the insulating layer 112 and the semiconductor thin film 113 are patterned, a protective film may be formed on the entire surface of the substrate. The subsequent steps are substantially the same as those in the first embodiment, and will be described briefly.
[0047]
As shown in FIG. 11B, the surface of the protective film 114 is irradiated with the first laser beam with the first laser beam 115 having the light intensity distribution as described above. The main gradient directions 116 and 116a of the light intensity in the first laser irradiation are set based on the azimuth display index shown on the insulating material substrate 111. In this embodiment, the main gradient directions 116 and 116a and the direction indicated by the azimuth display index are made to coincide. By this first laser irradiation, the irradiation region of the semiconductor thin film 113 is converted into the crystallized semiconductor thin film 117.
[0048]
Next, as shown in FIG. 11C, under the same conditions as in the first embodiment, the second laser irradiation is performed with the second laser light 118 shifted in the lateral direction by about 1 / 2P. As a result, as shown in FIG. 11 (d), the crystallized semiconductor thin film 117 becomes a single crystallized semiconductor thin film 109. The crystal grain surface form of the crystallized semiconductor thin film 117 is a quadrangular shape, and the plane orientation along the reference of the insulating material substrate 111 is a (100) plane. Therefore, according to the method of the present embodiment, a rectangular single crystallized region array having a (100) plane orientation in one direction of the cross section of the insulating material substrate can be formed.
[0049]
Third Embodiment A semiconductor thin film crystallization method and a crystallization apparatus according to an embodiment will be described with reference to FIGS. 12, 13, 14, and 15, respectively. In these examples, an excimer laser 121 (for example, XeCl, KrF, ArFF, etc.) is used as a light source, but is not necessarily limited thereto.
[0050]
As shown in FIG. 12A, on the exit side of the excimer laser 121 that emits the pulsed laser beam 122a, the energy density of the laser beam 122 (critical value j1 and critical value j2 shown in FIG. 5A) is set. An attenuator 123 for controlling and a homogenizing optical system 124 for making the intensity of the laser light uniform are sequentially arranged. The position indicated by reference numeral 120a is the image plane (focal plane) of the homogenizing optical system 124. On the exit side of the homogenizing optical system 124, a projection lens 125 that arranges the image forming surface 120a of the homogenizing optical system at the same magnification or reduction is disposed via a 90-degree reflecting mirror. The first phase shifter 126a is disposed on the image forming surface 120b (focus position) of the projection lens 125, and the second phase shifter 127a is disposed at a position deviated from the focus position (defocus position). Has been. Here, the second phase shifter 127a may be composed of a plurality of phase shifters, for example, two phase shifters whose phase shift directions are orthogonal to each other. The first phase shifter 126a is for forming a steep bottom in the laser light intensity distribution 81 shown in FIG. The second phase shifter 127a is for forming a gradient necessary for crystal growth in the horizontal direction in the laser light intensity distribution 81 shown in FIG. That is, in the laser light intensity distribution 81 shown in FIG. 8A, the bottom shape having a steep laser light intensity distribution at the minimum light intensity point 62a is formed by the first phase shifter 126a. In the laser light intensity distribution 81, the shape that becomes the maximum laser light intensity distribution from the minimum light intensity point 62a is a gradient necessary for crystal growth in the lateral direction, and is formed by the second phase shifter 127a.
[0051]
The first and second phase shifters 126a and 127a are fixed on the optical axis by a holder (not shown). This holder is incorporated in a drive mechanism DM such as a goniometer having a mechanism for moving in a direction along the optical axis and a direction perpendicular thereto, and a biaxial rotation mechanism.
[0052]
A sample 128 placed on the stage 129 is positioned on the emission side of the second phase shifter 127a. The stage 129 is movable in the X direction and the Y direction, and the sample 128 can be shifted in the horizontal direction relative to the second phase shifter 127a.
[0053]
Next, the operation of the crystallization apparatus having the above configuration will be described below.
[0054]
The pulsed laser beam 122a emitted from the excimer laser 121 is controlled in energy density by an attenuator 123 and enters a homogenizing optical system 124, where it becomes a laser beam 122b having a uniform intensity and is incident on a reflecting mirror. . Here, the laser beam 122b is deflected by 90 degrees in the direction of the sample 128 and is incident on the projection lens 125. The projection lens 125 causes the incident laser light 122b to be incident on the sample surface as laser light 122d modulated by the first and second phase shifters 126a and 127a. The configuration of the phase shifters 126a and 127a for this purpose will be described later with reference to FIG. Note that the sample 128 may actually be, for example, a laminated thin film substrate formed on any of the substrates shown in FIG. 9 and having the semiconductor thin film 113 shown in FIGS. 10 and 11.
[0055]
The characteristic of the laser light intensity distribution (image) formed by being modulated by the second phase shifter 127a is, for example, macroscopically at the millimeter level, such as a laser light intensity distribution 81 shown in FIG. It has uniform intensity and is micron-level microscopically intensity-modulated. When the first laser irradiation is performed with the laser light having such a laser light intensity distribution 81, a crystallized thin film in which the position of crystal grains is controlled as shown in the scanning electron micrograph of FIG. 8B may be formed. it can.
[0056]
When the energy density of the laser beam is optimized by the attenuator 123 and the surface of the sample 128 is irradiated with the laser beam 122d, the semiconductor thin film of the sample 128 rises in temperature by absorbing the laser beam 122d. Here, in the intensity modulation region of the laser beam 122d, it is desirable that the semiconductor thin film at the minimum intensity is in a molten state up to the vicinity of the base interface, and at the maximum intensity, the temperature is such that the semiconductor thin film does not evaporate.
[0057]
The first and second phase shifters 126a and 127a are formed on one surface of a transparent substrate, for example, a synthetic quartz plate 141a (142a) as shown by reference numerals 141 and 142 in FIGS. 14 (a) and 14 (b), respectively. In addition, an elongated rectangular groove 141b (142b) having a predetermined interval from each other is formed to form a stepped structure. The height of the step (groove depth) Δt corresponds to the phase difference θ of the emitted laser light. This phase difference θ is given by θ = 2πΔt (n−1) / λ. Here, λ is the wavelength of the laser, and n is the refractive index of the synthetic quartz plate. For example, when a KrF excimer laser with a wavelength of 248 nm is used, the refractive index is 1.508, and the phase difference is 180 ° when the step Δt is 244 nm. Such phase shifters 141 (126a) and 142 (127a) are provided at positions as shown in FIG. 12A in such a positional relationship that the grooves are orthogonal to each other. As a method of forming a step on the surface of the synthetic quartz substrate 141a (142a), for example, a method of etching using reactive ion etching, a method of direct processing using a focused ion beam method, a method of forming on the synthetic quartz substrate There is a method of thermally oxidizing an amorphous silicon thin film formed and patterned. The phase shifters 141 and 142 are different in groove dimension and pitch P (interval between phase shift lines) in the drawing, but may be the same.
[0058]
In addition to the surface step, the phase shifter may have an effect of forming a light intensity distribution by light absorption. For this purpose, for example, a light absorption film (for example, a film of SiN, SiON, Ge or the like) is formed on one surface of the synthetic quartz plate 141a (142a) and patterned. By using such a phase shifter 141 (142), the light intensity distribution changes depending on the absorption coefficient and the film thickness of the light absorption film. This method is preferable when forming in the region of the phase shifter where it is desired to suppress the light intensity vibration.
[0059]
In addition, an effect of forming a light intensity distribution may be added by forming a microlens on the surface of the phase shifter.
[0060]
As shown in FIG. 15, a plurality of pairs of phase shifters 152a and 152b, and 153a and 153b are provided on the same substrate by forming steps of different structures on the surface of a single synthetic quartz substrate 151. May be. In this example, two pairs of phase shifter regions 152a and 152b and 153a and 153b having different groove widths and distances between grooves (ie, phase shift portion pitch) are provided. In this case, the area of each phase shifter region must be larger than the cross section 154 of the incident laser light. Each pair of phase shifter regions 152a (153a) and 152b (153b) has a structure that is shifted by a half cycle (shifted by 1/2 phase shifter pitch). In such a phase shifter, the first irradiation uses one phase shifter (region) 152a, and the second irradiation moves the synthetic quartz substrate 151 in the longitudinal direction of the groove and the other phase shifter (region) 152b. Can be used for crystallization. The same applies to the other pair of phase shifters (regions) 153a and 153b. By using different pairs of phase shifters, the laser light can have different patterns of laser light intensity distribution.
[0061]
As shown in FIGS. 14C and 14D, the first phase shifter 141 and the second phase shifter 142 are attached by sandwiching four spacers 143 provided at the corners. An integral structure may be used. Further, a frame-shaped shield spacer may be provided between the four sides in place of the four spacers so that dust and the like can be prevented from entering between the phase shifters. In FIG. 14C, the first phase shifter 141 and the second phase shifter 142 are arranged such that one (in this case, the former) rectangular groove is inside and the other (in this case, the latter) rectangular groove is An example of combination on the outside is shown. FIG. 14D shows an example in which the first phase shifter 141 and the second phase shifter 142 are combined so that the rectangular grooves of both are inside. Of course, both phase shifters 141 and 142 may be combined so that the rectangular groove is on the outside. Instead, as shown in FIG. 14 (e), the first phase shifter and the second phase shifter may be integrally formed on one synthetic quartz substrate (common transparent substrate). The first phase shifter groove, that is, a step is formed on one surface, and the second phase shifter groove, that is, a step is formed on the other surface. Furthermore, the first phase shifter and the second phase shifter may interchange the installation positions in the optical path.
[0062]
The light intensity distribution obtained by the first and second phase shifters 126a and 127a as described above is the geometric structure of the surface step of the transparent substrate (synthetic quartz substrate), the angle of incident light, and the spatial coherence of light. Determined by gender. Depending on the required light intensity, only the second phase shifter 127a may be required.
[0063]
Fourth embodiment (not shown)
In the third embodiment, the same position of the surface of the sample 128 as that of the fourth embodiment is arranged on the focal plane of the projection lens 125. For example, the phase shifter 126a is provided on the focal plane 120a of the homogenizing optical system 123. It may be arranged. In this case, the diversification of the light intensity distribution design is limited as compared with the third embodiment, but there is an effect of improving the uniformity.
[0064]
In the embodiment of the crystallization apparatus described below, the same reference numerals are assigned to the substantially same portions as those in the third embodiment, and the description thereof is omitted.
[0065]
Fifth Embodiment In this apparatus, as shown in FIG. 12B, the first phase shifter 126a is arranged on the focal plane 120a of the homogenizing optical system 123, and the sample 128 is placed at the focal position of the imaging lens 125. The surface is located. The second phase shifter 127a is disposed at a position out of focus of the imaging lens 125. In this case, the diversity of the light intensity distribution design is improved as compared with the fourth embodiment, but the intensity modulation of the first phase shifter 126a is limited by the resolution of the projection lens.
[0066]
Sixth Embodiment In this apparatus, as shown in FIG. 12 (c), the first phase shifter 126a is disposed on the focal plane 120a of the homogenizing optical system 123, and the defocusing position of the homogenizing optical system 123 is shifted. In addition, a second phase shifter 127a is arranged. The surface of the sample 128 is disposed on the focal plane of the projection lens 125. In the apparatus having such a configuration, since there is no phase shifter near the sample surface, the degree of freedom around the stage 129 is increased. However, the light intensity distribution has a drawback of being limited by the resolution of the projection lens.
[0067]
In the third to sixth embodiments, the second laser irradiation is performed by relatively translating the sample 128 and the optical system (the phase shifters 126a and 127a and the projection lens 125), that is, the stage 129. Is moved relative to the optical system, or the optical system (specifically, the portion on the stage 129 side from the reflecting mirror) is moved relative to the stage 129 to translate the light intensity distribution. However, the present invention is not limited to such a method. This example will be described below as seventh and eighth embodiments. In these embodiments, two phase shifters 127c and 127d having the same configuration are used as the phase shifter. One phase shifter 127c is for the first laser irradiation, and the other phase shifter 127d is for the second laser irradiation. For this reason, when the growth edge of a crystal grain grown from the minimum light intensity line or the minimum light intensity point of the laser light modulated by the first phase shifter 127c is a Δ-shaped crystal grain, The relative positions of the phase shifters 127c and 127d are set so that the base region of the laser beam is irradiated with the minimum light intensity line or the minimum light intensity point of the laser light modulated by the second phase shifter 127d. ing. Further, the phase shifters 127c and 127d are arranged on the respective focal planes of the homogenizing optical system, but are not limited to these positions.
[0068]
Seventh Embodiment As shown in FIG. 13A, this apparatus includes a first excimer laser 121a, a first attenuator 123a, a first homogenizing optical system 124a, and a first phase shifter 127c. A second laser comprising a first laser irradiation optical system comprising: a second excimer laser 121b; a second attenuator 123b; a second homogenizing optical system 124b; and a second phase shifter 127d. And an optical system for irradiation. The first phase shifter 127c and the second phase shifter 127d have the same structure, but the periodic structure of the surface step is shifted by a half period. These phase shifters 127c and 127d use the phase shifter having the composite structure shown in FIGS. 14C and 14D, but may be a single structure phase shifter shown in FIG. 14B. A common half mirror 135 is disposed on the emission side of the first phase shifter 127c and the emission side of the second phase shifter 127d. The half mirror 135 has a function of reflecting the laser beam from the first phase shifter 127c by 90 ° to the imaging lens 125, and transmits the laser beam from the second phase shifter 127d to guide it to the imaging lens 125. With functions. The laser light that has passed through the imaging lens 125 irradiates the sample 128 with a light modulation intensity distribution that is shifted by about ½ P (1/2 of the phase shifter step pitch) in the lateral direction.
[0069]
In the apparatus having the above structure, the first excimer laser 121a and the second excimer laser 121b are controlled to oscillate alternately, and the first laser irradiation and the second laser irradiation are performed by the half mirror 135 and the projection lens 136. Are alternately performed so that these irradiations do not overlap with each other, thereby crystallizing the semiconductor thin film. In such a method, since it is not necessary to move the phase shifter for the second laser irradiation, it is possible to eliminate the movable part in the optical system, to eliminate the drive mechanism for this, and to stabilize the optical axis. There is a feature to become.
[0070]
Eighth Embodiment As shown in FIG. 13B, a beam splitter such as a half mirror 139 a is provided on the exit side of the excimer laser 121 via an attenuator 123. The half mirror 139a branches the incident laser light into two laser lights. On the transmission side of the half mirror 139a, a common half mirror 135 is disposed through a first homogenizing optical system 124a and a first phase shifter 127c in this order. A second homogenizing optical system 124b is arranged on the reflection side of the branching half mirror 139a via two mirrors 139b and 139c. The common half mirror 135 is disposed on the exit side of the homogenizing optical system 124b via a second phase shifter 127d. The common half mirror 135 reflects the laser light from the first phase shifter 127 c and transmits the laser light from the second phase shifter 127 d to guide it to the projection lens 125.
[0071]
In such an apparatus, the pulsed laser beam emitted from the laser 121 is branched into two laser beams by the half mirror 139b, and the first laser beam is transmitted through the first homogenizing optical system 124a and the first laser beam. The sample 128 is irradiated through the phase shifter 127c, the common half mirror 135, and the projection lens 125. The second laser light is applied to the sample 128 through the mirrors 139b and 139c, the second homogenizing optical system 124b, the second phase shifter 127d, and the projection lens 125. The optical path lengths of the first laser beam and the second laser beam are such that the sample is first irradiated with the first laser beam, and the sample is irradiated with the second laser beam after the irradiation is completed. Is set.
[0072]
Such a technique also has the same effect as that of the seventh embodiment.
[0073]
In the above embodiment, the first phase shifters 126a and 127c are configured to form a steep bottom, and the second phase shifters 127a and 127d are configured to form a gradient necessary for lateral crystal growth. An example was described. Furthermore, both the first phase shifters 126a and 127c and the second phase shifters 127a and 127d may be configured to form the same steep bottom, or a gradient necessary for lateral crystal growth may be formed. You may make it the structure for doing.
[0074]
A semiconductor device according to a ninth embodiment and a manufacturing method thereof will be described below with reference to FIG.
[0075]
As shown in FIG. 16A, a transparent rectangular substrate 301 (formed of an orientation indicator shown in FIG. 9B is formed of an insulating material such as alkali glass, quartz glass, plastic, polyimide, or the like. The underlayer 302, the amorphous semiconductor thin film 303, and the protective film 304 are sequentially formed on a flat surface (only a part of which is shown in the figure) in the order of known film formation such as chemical vapor deposition and sputtering. Form using technology. The underlayer 302 is formed of, for example, a laminated film of a SiN film 302a having a thickness of 50 nm and a SiO ₂ film 302b having a thickness of 300 nm. The SiN film 302a prevents impurities from the substrate 301 made of glass or the like from diffusing into the amorphous semiconductor thin film 303, and the SiO ₂ film 302b is formed of nitrogen from the SiN film 302a that is amorphous. The diffusion to the semiconductor thin film 303 is prevented. The amorphous semiconductor thin film 303 has a thickness of about 50 nm to 200 nm, for example, and is made of a semiconductor such as Si, Ge, or SiGe, in this embodiment, Si. The protective film 304 is the same as the protective film 104 described with reference to FIG.
[0076]
Next, the surface of the amorphous semiconductor thin film 303 was optically modulated by a phase shifter (for example, the phase shifter 141 shown in FIG. 14A) as the first laser light irradiation through the protective film 304. As will be described in detail later, a region 305 (hereinafter referred to as an irradiation region) irradiated with each of the first laser beams 105 and a region 306 (hereinafter referred to as a non-irradiation region) that are not irradiated are adjacent to each other. In order to facilitate understanding, only one unit region consisting of one irradiation region and one non-irradiation region is selectively irradiated so as to form a large number of unit regions. Show). Next, the substrate 301 is shifted laterally by about ½ of the pitch of the groove of the phase shifter, and the second laser beam 108 is used for the second laser irradiation. By such first and second laser irradiations, the irradiated region 305 is annealed and melted, and is converted into an amorphous or polycrystalline semiconductor thin film or a single crystal thin film. That is, the irradiation region 305 is formed of quadrangular crystal grains having a (001) plane at least in the crystal growth direction. The amorphous semiconductor in the irradiation region 306 is maintained as it is. For example, in the manufacturing process of the liquid crystal display device, the irradiation region 305 is a region for forming a driving circuit TFT that requires fast switching characteristics. The non-irradiation region 306 is a region for forming a pixel TFT that requires a high withstand voltage. Next, as shown in FIG. 16C, the protective film 304 is removed by etching to expose the semiconductor thin film.
[0077]
Then, using the photolithography technique, the irradiated region 305 and the non-irradiated region 306 are selectively etched to form two first island regions 305a and one second island region 306a. A gate insulating film 307 made of SiO ₂ and having a thickness of about 20 nm to 300 nm is formed on the substrate including the island-like regions 305a and 306a (precisely, on the base layer 302) as described above. It forms using. Gate electrodes 308 are formed on portions of the gate insulating film 307 facing the central portions of the island regions 305a and 305b, respectively. These gate electrodes 308 can be formed by patterning a layer of silicide or MoW.
[0078]
Next, as shown in FIG. 16D, impurity ions 309 are implanted into the island regions 305a and 306a using the gate electrode 308 as a mask, and a channel region is sandwiched between the source region and the drain region. Forming a region. At this time, the positions of the source region and the drain region are set so that the cross section in the direction of current flow in the channel region becomes the (001) plane. This setting is easily made based on the orientation instruction index formed on the substrate. The current that flows is (001) The impurity ion is an N-type impurity, for example, phosphorus if an N-channel MOS transistor is formed, and a P-type impurity, for example, if a P-channel MOS transistor is formed. Boron. The resulting device is annealed (at 450 ° C. for 1 hour) in a nitrogen atmosphere to activate the implanted impurities.
[0079]
Next, an interlayer insulating film 330 made of, for example, SiO ₂ is formed on the gate insulating film 307 including the gate electrode 308. The portions of the interlayer insulating film 130 and the gate insulating film 307 on the regions (source region and drain region) doped with impurities in the island regions 305a and 306a are removed by selective etching to form contact holes.
[0080]
Next, as shown in FIG. 16E, a source electrode 311a and a drain electrode 311b electrically connected to the source region and the drain region through contact holes are formed on the gate insulating film 307. Thus, a thin film semiconductor device is completed.
[0081]
FIGS. 17A and 17B show an example of a liquid crystal display device manufactured using the thin film semiconductor device.
[0082]
The liquid crystal display device 400 includes a pair of front and rear transparent substrates (base layers) 421 and 422, a liquid crystal layer 423, a pixel electrode 424, a scanning wiring 425, a signal wiring 426, a counter electrode 427, a TFT 430, and the like.
[0083]
As the pair of transparent substrates 421 and 422, for example, a pair of glass plates can be used. The transparent bases 421 and 422 are joined via a frame-shaped sealing material. The liquid crystal layer 423 is provided in a region surrounded by a sealing material between the pair of transparent substrates 421 and 422.
[0084]
A plurality of pixel electrodes 424 provided in a matrix in the row direction and the column direction on one transparent substrate of the pair of transparent substrates 421 and 422, for example, the inner surface of the rear transparent substrate 422, and a plurality of pixel electrodes 424 A plurality of TFTs 430 (semiconductor devices according to the present invention described in detail above) electrically connected to the pixel electrode 424 and scanning wirings 425 and signal wirings 426 electrically connected to the plurality of TFTs 430 are provided. ing.
[0085]
The scanning wiring 425 is provided along the row direction of the pixel electrode 424. One ends of these scanning wirings 425 are respectively connected to a plurality of scanning wiring terminals (not shown) provided at one side edge of the transparent substrate 422 on the rear side. The plurality of scanning wiring terminals are connected to the scanning line driving circuit 41, respectively.
[0086]
The signal wiring 426 is provided along the column direction of the pixel electrode 424. One ends of these signal wirings 426 are connected to terminals (not shown) of a plurality of signal wirings 426 provided at one end edge of the transparent substrate 422 on the rear side. The plurality of signal wirings 426 terminals are connected to the signal line driving circuit 442, respectively.
[0087]
The scanning line driving circuit 741 and the signal line driving circuit 442 are connected to the liquid crystal controller 443, respectively. The liquid crystal controller 443 receives, for example, an image signal and a synchronization signal supplied from the outside, and generates a pixel video signal Vpix, a vertical anthem control signal YCT, and a horizontal scanning control signal XCT.
[0088]
On the inner surface of the transparent substrate 421 on the front side, which is the other transparent substrate, a single film-like transparent counter electrode 427 facing the plurality of pixel electrodes 424 is provided. A color filter is provided on the inner surface of the transparent substrate 421 on the front side so as to correspond to the plurality of pixel portions where the plurality of pixel electrodes 424 and the counter electrode 427 face each other, and light shielding is performed corresponding to the region between the pixel portions. A film may be provided.
[0089]
A polarizing plate (not shown) is provided outside the pair of transparent substrates 421 and 422. In the transmissive liquid crystal display device 400, a surface light source (not shown) is provided on the rear side of the transparent substrate 422 on the rear side. Note that the liquid crystal display device 400 may be a reflective type or a transflective type.
[0090]
In the embodiment described above, the TFT is described as the semiconductor device. However, the present invention can be applied to other semiconductor elements based on a semiconductor thin film, for example, a diode.
[0091]
Although a liquid crystal display device has been described as a display device using a semiconductor element, the present invention is not limited to this and can be applied to, for example, an organic EL display device.
[0092]
Further, the phase shifter using light diffraction and interference has been described in the embodiment as an optical modulation element that emits incident laser light having a uniform light intensity distribution as laser light having a light intensity distribution having a minimum light intensity point. However, for example, other types of optical modulation elements that exhibit the above functions by utilizing reflection and / or absorption of light can also be used. Such an optical modulation element is formed, for example, by providing an absorption film or a reflection film at a position corresponding to a groove instead of forming a groove in the substrate with the phase shifters (141, 142) shown in FIG. .
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a conventional zone melting method.
FIG. 2 is a diagram for explaining an excimer laser crystallization method which is a conventional technique.
FIG. 3 is a diagram for explaining an SLS system that is a conventional technique;
FIG. 4 is a diagram for explaining a conventional phase modulation excimer laser crystallization method.
FIGS. 5A and 5B are diagrams for explaining the technology underlying the present invention, in which FIG. 5A is a diagram showing the light intensity distribution of a used laser beam, and FIG. 5B is a diagram of crystal grains of a crystallized thin film; The figure which shows the result of having measured the surface form and the crystallographic orientation of each crystal grain using the scanning electron microscope (SEM) method and the electron backscattering (EBSP) method, and (c) shows in (b) It is a figure which shows each crystal grain as a diagram.
FIGS. 6A and 6B are diagrams for explaining a technique that is the basis of the present invention, in which FIG. 6A is a top view schematically showing crystal grains produced by first phase modulation excimer laser irradiation, and FIG. FIG. 6C is a top view schematically showing crystal grains after irradiation of the phase-modulated excimer laser, and FIG. 6C is a diagram schematically showing the plane orientation of the crystal grains shown in FIG.
FIG. 7A is a view showing a scanning electron micrograph in a state where the second laser irradiation is performed so that the laser intensity maximum region in the first laser irradiation becomes a minimum region; FIG. It is a figure which shows the scanning electron micrograph of the crystallized thin film surface after laser irradiation.
FIGS. 8A and 8B are views for explaining the technology underlying the present invention, wherein FIG. 8A is a perspective view schematically showing first and second phase modulation excimer laser irradiations, and FIG. 8B is a second view. It is a figure which shows the crystal grain by which position control was carried out two-dimensionally after the phase-modulation excimer laser irradiation.
FIG. 9A is a plan view showing three examples of a circular substrate on which an orientation display index is formed, which can be used in the embodiment of the present invention, and FIG. It is a top view which shows three examples of the formed rectangular board | substrate.
FIG. 10 is a diagram for explaining the method according to the first embodiment of the present invention for each process.
FIG. 11 is a diagram for explaining the method according to the second embodiment of the present invention for each process.
FIGS. 12A to 12C are schematic diagrams for explaining a semiconductor thin film crystallization method and a crystallization apparatus according to third to sixth embodiments of the present invention, respectively.
FIGS. 13A and 13B are schematic views for explaining a semiconductor thin film crystallization method and a crystallization apparatus according to seventh and eighth embodiments of the present invention, respectively.
14 (a) is a perspective view showing a phase shifter for annealing, FIG. 14 (b) is a perspective view showing a phase shifter for positioning, and FIGS. 14 (c) to (e) are annealing views. FIG. 6 is a perspective view showing different configurations in which a phase shifter for positioning and a phase shifter for positioning are integrated.
FIG. 15 is a plan view for explaining a configuration in which an annealing phase shifter and a positioning phase shifter are formed on the same substrate;
FIG. 16 is a diagram for explaining the semiconductor device and the manufacturing method thereof according to the ninth embodiment of the present invention according to the process.
FIG. 17 is a diagram for explaining a liquid crystal display device including a semiconductor device manufactured according to the present invention.
[Explanation of symbols]
52 ... Small grain crystal grains, 53 ... Strip crystal grains, 54 ... Delta crystal grains, 81 ... Laser light intensity distribution, 82 ... Crystal growth start point, 103 ... Semiconductor thin film, 105 ... First laser irradiation laser Light, 106, 106a, main gradient direction, 107, crystallized polycrystalline semiconductor thin film, 108, second laser irradiation laser light, 141, 142, 126a, 127a, phase shifter.

Claims (19)

The incident laser beam is modulated by the first optical modulation element into a laser beam having a light intensity distribution having a minimal light intensity line extending in one direction, and the incident laser beam extends in a direction intersecting the one direction. Light intensity distribution laser light having light intensity lines is modulated by a second optical modulation element disposed at a different position on the optical path from the first optical modulation element, and these minimum light intensity lines intersect. Emitting a laser beam having a light intensity distribution having a minimum light intensity point;
A first laser irradiation step of irradiating a non-single-crystal semiconductor thin film from one side with the emitted laser light and growing crystal grains corresponding to the minimum light intensity point in a lateral direction from a crystal start point; A method for crystallizing a semiconductor thin film. After the laser irradiation step, the method further comprises a second laser irradiation step of crystallizing the semiconductor thin film by irradiating the crystal grains with laser light to further grow the crystal grains. The method for crystallizing a semiconductor thin film according to claim 1. After the laser irradiation step, the first and second optical modulation elements and the semiconductor thin film are relatively moved in a direction along the surface of the semiconductor thin film, and light having a minimum light intensity point in the semiconductor thin film By irradiating laser light of intensity distribution with the minimum light intensity point substantially corresponding to the growth edge of the crystal grain, and growing the crystal grain on the semiconductor thin film using the growth edge as the crystal growth starting point. 2. The semiconductor thin film crystallization method according to claim 1, further comprising a second laser irradiation step of crystallizing the semiconductor thin film. The first laser irradiation step includes a step of forming crystal grains having a predetermined plane orientation in the growth direction of the crystal grains and growing faster than other crystal grains,
In the second laser irradiation step, irradiation is performed such that the minimum light intensity point substantially corresponds to the growth end portion of the crystal grain that grows quickly, and the semiconductor thin film is crystallized using the growth end portion as a crystal growth starting point. 4. The method of crystallizing a semiconductor thin film according to claim 3, further comprising the step of growing crystal grains whose plane orientation in the growth direction is the predetermined plane. The first laser irradiation step includes a step of forming a crystal grain having a Δ shape when viewed from one side, with the plane orientation in the growth direction of the crystal grain being a (100) plane,
In the second laser irradiation step, irradiation is performed such that the minimum light intensity point substantially corresponds to the bottom region of the Δ-shaped crystal grains, and the bottom region is set as a crystal growth region to the semiconductor thin film in the crystal growth direction. 4. The method for crystallizing a semiconductor thin film according to claim 3, further comprising the step of growing crystal grains having a (100) plane orientation and a surface shape that is substantially rectangular when viewed from one side. An emission means for emitting laser light having a uniform light intensity distribution;
A supporting means for supporting the non-single-crystal semiconductor thin film;
Light intensities arranged at different positions on the optical path between the emission means and the support means and having first and second minimum light intensity lines by modulating the phase of the laser light emitted from the emission means. First and second optical modulation elements for emitting laser beams of distribution, respectively,
The first optical modulation element and the second optical modulation element have a light intensity distribution in which the first minimum light intensity line and the second minimum light intensity line intersect to have a minimum light intensity point. The modulated laser beam is irradiated on the semiconductor thin film from one side so that crystal grains corresponding to the minimum light intensity point grow laterally from the crystal growth point to the semiconductor thin film. A crystallization apparatus. Drive means for relatively moving the injection means and the support means in a direction along the surface of the semiconductor thin film;
The driving means irradiates the semiconductor thin film with a laser beam having a light intensity distribution having a minimum light intensity point, with the minimum light intensity point substantially corresponding to the growth edge of the crystal grain, and the growth edge. The first and second optical modulation elements and the semiconductor thin film are relatively moved in the direction along the surface of the semiconductor thin film so as to grow crystal grains on the semiconductor thin film starting from the crystal growth origin. The crystallization apparatus according to claim 6. The crystallization apparatus according to claim 7, wherein the driving unit moves at least one of the injection unit and the support unit. A homogenizing optical system that is provided on each of the optical paths and uniformizes the light intensity of the laser light emitted from the emitting means; and a projection lens that equalizes or reduces the imaging surface of the homogenizing optical system. The crystallization apparatus according to any one of claims 6 to 8. The crystallization apparatus according to claim 9, wherein the first optical modulation element is disposed on an imaging plane of the homogenizing optical system. The crystallization apparatus according to claim 9, wherein the first optical modulation element is disposed on an imaging plane of the projection lens. The first optical modulation element is disposed on an image plane of the homogenizing optical system, and the second optical modulation element is disposed on an image plane of the projection lens. The crystallization apparatus according to claim 9. 10. The crystal according to claim 9, wherein one surface of the semiconductor thin film is positioned on the imaging surface of the projection lens, and a first phase shifter is disposed on the imaging surface of the homogenizing optical system. Device. The first and second optical modulation elements respectively require first and second phase shifters for emitting laser light having a light intensity distribution having a minimum light intensity line by modulating incident laser light. The crystallization apparatus according to any one of 13. Each of the first phase shifter and the second phase shifter includes a transparent substrate having one surface, and a rectangular elongated groove extending in one direction parallel to the surface of the substrate at a predetermined interval. 15. The crystal according to claim 14, wherein the grooves have a depth of π with respect to one surface of the substrate, and a phase shift portion is defined between the grooves and the one surface. Device. 16. The crystallization apparatus according to claim 15, wherein the first phase shifter and the second phase shifter have different phase shift portions. The crystallization apparatus according to claim 15 or 16, wherein the first phase shifter and the second phase shifter are disposed so that their phase shift portions are orthogonal to each other. The crystallization apparatus according to any one of claims 14 to 17, wherein the first phase shifter and the second phase shifter are attached by spacer means arranged therebetween. The substrate of the first phase shifter and the substrate of the second phase shifter are integrally formed of a common transparent substrate, and the groove of the first phase shifter is formed on one surface of the common transparent substrate, The crystallization apparatus according to claim 14, wherein the groove of the second phase shifter is formed on the other surface of the common transparent substrate.

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