JP2005347741A - Laser irradiation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser irradiation apparatus capable of easily forming a laser beam having a homogeneous energy distribution and a shape required for annealing by arranging a slit, the length of an opening of which can be varied at an image-forming position of a diffractive optical element. <P>SOLUTION: In the laser irradiation apparatus comprising a laser oscillator, a diffractive optical element, and a slit, the opening of the slit can be varied in length in the lengthwise direction, the incidence in the direction toward a substrate is oblique, and further, the laser is a continuously oscillated solid-state, gas or metal laser, or a pulsed oscillation one having a frequency of 10 MHz or higher. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser irradiation apparatus (an optical system for guiding a laser and a laser beam output from the laser to an irradiated body) for uniformly and efficiently performing annealing, for example, performed on a semiconductor material. Apparatus).

  In recent years, a technique for manufacturing a thin film transistor (hereinafter referred to as TFT) on a substrate has greatly advanced, and application development to an active matrix display device has been advanced. In particular, a TFT using a polycrystalline semiconductor film has higher field-effect mobility than a TFT using a conventional amorphous semiconductor film, and thus can operate at high speed. For this reason, it has been attempted to form a drive circuit provided outside the conventional substrate on the same substrate as the pixel and to control the pixel with the drive circuit.

  By the way, with the increase in demand for semiconductor devices, it is strongly demanded to lower the temperature and shorten the manufacturing time. As a substrate used for a semiconductor device, a glass substrate, which is more advantageous than a single crystal semiconductor substrate in terms of cost, has been adopted. A glass substrate is inferior in heat resistance and easily deformed by heat, but when a TFT using a polycrystalline semiconductor film is formed on a glass substrate, the semiconductor film can be easily crystallized at a low temperature by using laser annealing. It can be carried out.

  At the same time, laser annealing can significantly reduce the processing time compared to annealing methods using radiant heating or conduction heating, and the semiconductor film on the substrate can be selectively and locally heated to make the substrate almost thermally. It has the advantage of not damaging it.

Laser oscillators used for laser annealing are roughly classified into two types, pulse oscillation and continuous oscillation, depending on the oscillation method. In recent years, in crystallizing a semiconductor film, it is more preferable to use a continuous oscillation laser oscillator such as an Ar laser or a YVO ₄ laser than a pulse oscillation laser oscillator such as an excimer laser. It has been found that the diameter increases. As the crystal grain size in the semiconductor film increases, the number of grain boundaries entering the TFT channel region formed using the semiconductor film decreases, so that the mobility increases, which can be used for the development of higher performance devices. Therefore, continuous wave laser oscillators are in the spotlight.

  However, when laser annealing is performed using a continuous wave laser irradiator, there is a problem that the state of annealing becomes uneven on the irradiated surface. The cause is that the laser beam emitted from the continuous wave laser irradiator has a Gaussian energy distribution, and has a characteristic that the energy decreases from the center toward the end. Therefore, it is difficult to anneal uniformly.

  A laser irradiation apparatus shown in FIG. 6 is known as an apparatus that linearizes the shape of the laser beam on the irradiation surface and makes the energy of the laser beam uniform. The laser irradiation apparatus has a plurality of cylindrical lens arrays and the like, and the laser beam emitted from the laser oscillator 1 is divided or condensed into a plurality of lights by the plurality of cylindrical lens arrays 2 to 6, and The convex cylindrical lenses 5 and 6 whose directions are orthogonal to each other, and a doublet cylindrical lens 8 composed of two cylindrical lenses after being reflected by the mirror 7, the plurality of lights are again converted into one linear laser beam. And is condensed and irradiated onto the irradiation surface 9.

  Then, by irradiating the linear beam formed in the above configuration while shifting in the short direction of the laser beam, the entire surface of the amorphous semiconductor is crystallized by laser annealing or crystallinity is improved. Improvement or activation of impurity elements will be performed.

  However, the conventional laser irradiation apparatus uses a plurality of expensive cylindrical lens arrays as described above, and it is necessary to arrange them so that a desired linear beam is formed. There was a problem that the cost increased. Further, when laser annealing is performed, the linear beam is processed into a desired size, but when the size is changed again, it is necessary to rearrange the optical system or replace optical components. Therefore, optical adjustment is required every time the size of the linear beam is changed, and the optical adjustment requires a lot of time, so that there is a problem that the throughput is low (see Patent Document 1).

  The present applicant has already proposed a compact and low-cost laser irradiation apparatus that eliminates the disadvantages of these conventional laser irradiation apparatuses. The laser irradiation apparatus is shown in FIG. This laser irradiation apparatus uses a diffractive optical element which is an element capable of forming a rectangular beam having a uniform energy distribution.

  That is, the laser beam emitted from the laser oscillator 11 is reflected by the mirror 12, and then formed into a rectangular beam 14 having a uniform energy distribution by the diffractive optical element 13, which has a rectangular shape and an energy distribution. An irradiation surface 15 is arranged at a position where a uniform beam 14 is imaged (see Patent Document 1).

However, even in the above laser irradiation apparatus, the end of the rectangular beam is not uniform, and in order to change the beam size, it is necessary to replace the diffractive optical element or other lens, or to change the arrangement of the optical element. For example, there is a problem that the optical adjustment takes time and the throughput is low.
JP 2003-257885 A

  An object of the present invention is to solve the above-described problem. Specifically, an energy distribution is provided by disposing a slit having a variable slit opening length at an imaging position of a diffractive optical element. An object of the present invention is to provide a laser irradiation apparatus that is uniform and can easily form a laser beam having a shape necessary for annealing.

  In order to achieve the above object, the present invention adopts the following configuration. The laser annealing method referred to here is a technique for recrystallizing a damaged layer or an amorphous layer formed on a semiconductor substrate or a semiconductor film, or a laser irradiation to an amorphous semiconductor film formed on a substrate. It refers to a technique for crystallizing a semiconductor film, a technique for crystallizing an amorphous semiconductor film formed on a substrate by introducing an element that promotes crystallization, such as nickel, and then performing laser irradiation. Moreover, the technique applied to planarization and surface modification of a semiconductor substrate or a semiconductor film is also included. Further, in this specification, laser beams whose shapes on the irradiation surface are linear, elliptical, and rectangular are referred to as a linear beam, an elliptical beam, and a rectangular beam, respectively.

  One of the inventions disclosed in this specification is a laser irradiation apparatus including a laser oscillator, a diffractive optical element, a slit, and a condensing lens, wherein the slit can change the length of the slit opening. It is characterized by.

  According to another aspect of the invention, there is provided a laser irradiation apparatus having a laser oscillator, a diffractive optical element, a slit, and a condenser lens, wherein the slit can change the length of the slit opening, and It is possible to irradiate laser beams having different lengths.

  According to another aspect of the present invention, there is provided a laser irradiation apparatus having a laser oscillator, a diffractive optical element, a slit, and a condenser lens, wherein the slit can change the length of the slit opening, and On the other hand, laser beams having different lengths can be irradiated obliquely.

  Another aspect of the invention is characterized in that the length of the slit opening in the longitudinal direction is variable.

  In the above configuration, the slit is positioned between the diffractive optical element and the condenser lens and is positioned on the optical path of the laser beam emitted from the laser oscillator.

In another aspect of the invention, the laser from the laser oscillator is a continuous wave laser or a pulsed laser having an oscillation frequency of 10 MHz or more. As the continuous wave laser, (1) single crystal YAG, YVO ₄ , YLF, YAlO ₃ , GdVO ₄ , alexandrite, Ti: sapphire, or polycrystalline YAG, Y ₂ O ₃ , YVO ₄ , YAlO ₃ , GdVO _{3 4.} Laser using a medium containing one or more of Nd, Yb, Cr, Ti, Ho, Er, Tm, and Ta as dopants, (2) Ar laser, Kr laser, CO ₂ laser And a gas laser. Further, as a pulse laser with an oscillation frequency of 10 MHz or more, single crystal YAG, YVO ₄ , GdVO ₄ , or polycrystalline YAG, Y ₂ O ₃ , YVO ₄ , YAlO ₃ , GdVO ₄ are doped with Nd, Yb, Cr , Ti, Ho, Er, Tm, and Ta may be used as a medium.

  According to the present invention, first, a laser beam emitted from a laser oscillator passes through a diffractive optical element, thereby forming a linear, elliptical, or rectangular laser beam cross section with a uniform energy distribution on the slit, By projecting onto the irradiation surface, a laser beam with a uniform energy distribution can be formed on the irradiation surface. By performing annealing using this laser beam, uniform annealing can be performed on the amorphous semiconductor film on the substrate.

  In addition, by changing the length of the slit opening in the longitudinal direction in a direction perpendicular to the traveling direction of the laser beam, the end of the rectangular beam can be shielded and shaped to the desired size. Can do. Therefore, optical adjustment and replacement of optical components are not required, and rectangular beams of various sizes can be formed in a short time.

  Furthermore, since the size of a rectangular beam to be used can be easily changed depending on a device to be manufactured, as a result, a large number of substrates can be processed in a short time, and throughput can be increased. In addition, since uniform annealing can be performed on the substrate, the uniformity of crystallinity within the substrate surface can be improved. Therefore, variation in electrical characteristics can be reduced, and reliability can be increased. If the present invention is applied to a TFT mass production line, a TFT having high operating characteristics can be efficiently produced.

  As a result, in a semiconductor device typified by an active matrix liquid crystal display device, the operating characteristics and reliability of the semiconductor device can be improved. Further, in the manufacturing process of the semiconductor device, the margin can be increased and the yield can be improved, so that the manufacturing cost of the semiconductor device can be reduced.

  FIG. 1 shows an example of a laser irradiation apparatus of the present invention. First, a substrate 107 over which a non-single crystal semiconductor film 106 is formed is prepared. The substrate 107 is placed on the X-axis stage 108 and the Y-axis stage 109, and the X-axis direction and the Y-axis direction are moved by moving the X-axis stage 108 and the Y-axis stage 109 in the directions of arrows respectively by a motor (not shown). It can be moved freely.

The laser irradiation apparatus includes a schematic laser oscillator 101, a diffractive optical element 102, a slit 103, a mirror 104, and a condenser lens 105. As the condenser lens 105, a convex lens (a convex spherical lens or a convex cylindrical lens) can be used. The laser oscillator 101 is a known and continuous oscillation type laser, that is, as a solid-state laser, single crystal YAG, YVO ₄ , YLF, YAlO ₃ , GdVO ₄ , alexandrite, Ti: sapphire, or polycrystalline YAG, Y ₂ O ₃ , YVO ₄ , YAlO ₃ , GdVO ₄ , any of lasers using one or more of Nd, Yb, Cr, Ti, Ho, Er, Tm, and Ta as dopants as a medium As the gas laser, any of Ar laser, Kr laser, and CO ₂ laser is used. Alternatively, even in the case of a pulsed laser, single crystal YAG, YVO ₄ , GdVO ₄ having a frequency of 10 MHz or more, or polycrystalline YAG, Y ₂ O ₃ , YVO ₄ , YAlO ₃ , GdVO ₄ are doped with Nd as a dopant. , Yb, Cr, Ti, Ho, Er, Tm, and Ta may be used as a medium. As described above, by using a continuous oscillation type laser oscillator 101 or a pulse laser having a frequency of 10 MHz or more, a semiconductor film having a grain size capable of forming one TFT in at least one crystal grain is formed. can do.

  The reason why not only a continuous wave laser but also a pulse laser having a high oscillation frequency may be used for the annealing treatment of the semiconductor film is as follows. It is said that the time from when the semiconductor film is irradiated with the laser beam until the semiconductor film is completely solidified is several tens to several hundreds nsec. Therefore, in a pulse laser with a low oscillation frequency, the next pulse is irradiated after the semiconductor film is melted and solidified by the laser. Therefore, after each pulse is irradiated, the crystal grains grow radially in a central symmetry during recrystallization. Since grain boundaries are formed at the boundaries between adjacent crystal grains, irregularities occur on the surface of the semiconductor film.

  However, when a pulse laser having a high oscillation frequency is used, the semiconductor film is irradiated with the next pulse after the semiconductor film is melted by the laser and solidified. Therefore, unlike the case of using a pulse laser having a low oscillation frequency, the solid-liquid interface can be continuously moved in the semiconductor film. Accordingly, a semiconductor film having crystal grains continuously grown in the laser scanning direction is formed.

  The diffractive optical element 102 is also referred to as a diffractive optical element (DOE) or a diffractive optic, and is an element that obtains a spectrum by utilizing light diffraction. A condensing lens is formed by forming a number of grooves on the surface thereof. The one with the function is used. By using this diffractive optical element 102, the energy distribution in the Gaussian distribution of the laser beam emitted from the continuous oscillation laser oscillator 101 can be formed into a rectangular beam having a uniform energy distribution. .

  The slit 103 is a flat plate member disposed at the image formation position of the diffractive optical element 102, and is formed at a position where a beam formed by the diffractive optical element 102 is formed in a rectangular shape with a uniform energy distribution. Be placed. The outline is shown in FIG. The slit 103 has a rectangular slit opening 110 at the center thereof, and the both ends 115a and 115b in the longitudinal direction of the slit opening 110 are shielded to open and shield the both ends 115a and 115b. Plates 113a and 113b are provided. The slit 103 may be arranged so that the direction in which the shielding plates 113a and 113b are moved is parallel to the surface of the diffractive optical element 102 that receives the laser beam.

  Supporting pieces 114 each having a circular hole 116 with an internal thread formed on the inner surface are attached to substantially the central portions of the respective shielding plates 113a and 113b. In addition, a motor 111 for attaching one end of the screw shaft 112 and rotating the screw shaft 112 on the opposite side to the slit 103 of each shielding plate 113a, 113b is disposed. The other end is screwed into a female screw formed in the hole 116 of the support piece 114 of the shielding plates 113a and 113b. Therefore, when the motor 111 is driven, the screw shaft 112 is rotated, and the shielding plates 113a and 113b are moved along the longitudinal direction of the slit opening 110 via the support piece 114 as indicated by the arrows, thereby the slit opening. The length in the longitudinal direction of 110 is varied. As the motor 111, a linear motor or the like can be used. Further, if it is other than a motor, for example, an ultrasonic stage can be used. A piezo element or the like can be used if the stroke when opening and closing the slit is as small as 100 μm or less.

  Thus, the length of the slit opening 110 in the longitudinal direction can be varied by moving the shielding plates 113a and 113b in the left and right directions at both ends of the slit opening 110. Therefore, among the rectangular beam formed by the diffractive optical element 102, it is possible to cut a portion where the energy distribution at both ends in the longitudinal direction is not uniform, as necessary, and irradiate the beam with a uniform energy distribution. It can be formed on the surface. By performing annealing using this beam, uniform annealing can be performed on the amorphous semiconductor film on the substrate.

Further, the advantage of opening and closing the slit is not only to block a region where the energy distribution at both ends in the longitudinal direction of the beam is not uniform. There is also an advantage that the length in the longitudinal direction of the beam can be adjusted to a desired size according to the design rule of the irradiation surface. In this case, optical adjustment and replacement of optical components are not necessary.
Specifically, the beam length H can be varied according to the position of the TFT formed on the substrate 107 by moving the shielding plates 113a and 113b in the left-right direction. The variable form is shown in FIGS. Since the crystal 121 is not uniform in the portion 121 where the adjacent laser beams are irradiated, the TFT is not usually manufactured. However, there are cases where TFTs must be arranged at various positions in the design. In such a case, if scanning is performed with the same beam length H, the TFT is inevitably positioned at a location 121 where the laser beams are overlapped and irradiated.

  In FIG. 3, the beam length H is varied for each irradiation region. That is, in the irradiation region 1, the beam is scanned with a short beam length H 1 and crystallized so as to include all the production positions of the TFT 130 to be formed in the irradiation region 1. Next, in the irradiation region 2, the beam is scanned with a beam length H 2 that is longer than that of the irradiation region 1, and crystallization is performed so as to include all the production positions of the TFT 130 to be formed in the irradiation region 2. Further, in the irradiation region 3, the beam is scanned with a beam length H3 which is longer than that of the irradiation region 2, and crystallized so as to include all the production positions of the TFT 130 to be formed in the irradiation region 3. In this way, by changing the length of the slit opening 110 and changing the beam length H for each irradiation region, crystallization is performed so that the TFT 130 is not located at the spot 121 where the adjacent laser beams are overlapped and irradiated. be able to.

FIG. 4A shows an example in which the beam length H is changed during laser irradiation by the shielding plates 113a and 113b. That is, the beam length H is adjusted by moving the shielding plates 113a and 113b during irradiation according to the arrangement of the TFTs on the substrate, instead of changing the beam length H for each irradiation region as shown in FIG. In this case, it is individually avoided that the end of the beam overlaps the TFT forming portion.
That is, in the first irradiation area 201, the laser beam is irradiated with the beam length H1 in the area (area (1)) until it overlaps the formation portion of the TFT 203. Next, the beam length is changed by adjusting the shielding plates 113a and 113b before reaching the region where the end of the beam overlaps the formation portion of the TFT 203 (region (2)), and the beam length H2 longer than the beam length H1. To. By irradiating the laser beam with the beam length H 2, it is avoided that the end of the beam overlaps the formation portion of the TFT 203. Note that a margin may be provided when changing the width of the beam in order to surely prevent the end of the laser irradiation region from overlapping the formation portion of the TFT 203. In the region where the laser has passed the formation portion of the TFT 203 (region (3)), the beam length is returned to H1 and the laser is irradiated. In this way, the first irradiation region 201 is formed.
Similarly, in the second irradiation region 202, the laser is irradiated with the beam length H1 in the region (region (1)) until the beam overlaps the TFT 203 formation portion. Next, just before the end of the beam reaches the region where the TFT 203 is formed (region (2)), the shielding plates 113a and 113b are adjusted to make the beam length H3 shorter than the beam length H1, thereby forming the TFT 203. Irradiate to avoid parts. In the region (3) past the formation portion of the TFT 203, irradiation is performed by returning to the beam length H1.

  Further, in the present invention, as shown in FIG. 4B, irradiation can be performed while changing the beam irradiation direction. In the first irradiation region 201, similarly to FIG. 4A, the beam length H1 is changed to a beam length H2 to avoid the formation portion of the TFT 203, and the first region 201 is irradiated with laser. After that, the laser beam with a beam length H3 that is a length capable of irradiating the formation region of the TFT 203 to the second region 202 from a direction different from the first irradiation direction, for example, a direction orthogonal to the first irradiation direction. Irradiate. Specifically, (1) a method of changing the incident direction of the laser by changing the setting position of the optical system, and (2) a method of irradiating the beam after changing the direction of the substrate by rotating the stage. There are two. Either method is possible, but the latter is more preferable because it does not require replacement or readjustment of the optical system.

  With such a configuration, the laser beam emitted from the laser oscillator 101 is formed into a linear, elliptical, or rectangular beam with a uniform energy distribution by the diffractive optical element 102, and at the slit 103. Once imaged. After that, the beam passes through the slit 103, is reflected by the mirror 104, is further collected by the condenser lens 105, and is obliquely linear or elliptical with respect to the substrate 107 on which the non-single crystal semiconductor film 106 is formed. Or a rectangular beam 120. Then, the X-axis stage 108 or the Y-axis stage 109 is moved, and the laser scans over the entire surface of the non-single crystal semiconductor film 106.

  The rectangular beam 120 formed on the substrate 107 has a length in the longitudinal direction of about 150 to 400 μm and a length in the short direction of about 1 to 30 μm. Of the size of the beam 120, the length in the longitudinal direction may be determined according to the length in the short direction so that the energy density is sufficient for crystallization. Here, the lower limit of the length in the short direction is about 1 μm due to the limitation of optical design. The upper limit of the length in the short direction is about 30 μm. This is because if the length in the short direction exceeds the upper limit, the surface of the semiconductor film becomes rough, which is not preferable. Actually, if the length in the short direction is about 10 μm at 10 W, the length in the long direction is about 400 μm. If the length in the short direction is about 8 μm at 3 W, the length in the long direction is about 150 μm.

  Further, as described above, the beam 120 on the substrate 107 is incident obliquely because the interference with the reflected light from the lower surface of the substrate 107 is prevented. This point will be described with reference to FIG. When incident light 140 having a beam length W is incident on the substrate 107 on which the non-single-crystal semiconductor film 106 is formed obliquely at an incident angle θ, the upper surface reflected light 141 is generated from the upper surface of the substrate 107. On the other hand, light that has not been reflected by the upper surface of the substrate 107 travels into the substrate, and lower surface reflected light 142 is generated from the lower surface of the substrate 107. Here, it is known that light interference occurs when the upper surface reflected light 141 and the lower surface reflected light 142 respectively generated from the upper and lower surfaces of the substrate 107 overlap.

  When this interference occurs, the crystal at the occurrence location becomes non-uniform. However, as shown in FIG. 5, the upper surface reflected light 141 and the lower surface reflected light 142 can be prevented from overlapping by setting the incident angle θ to a predetermined angle or more. As described above, the incident light 140 is inclined and is incident on the substrate 107 so that the upper surface reflected light 141 and the lower surface reflected light 142 do not overlap with each other, thereby preventing adverse effects due to interference. If the incident angle θ is too large, crystallization cannot be performed. The appropriate angle of incidence θ depends on the thickness d of the substrate 107 and the beam length W. When the thickness d of the substrate 107 is about 700 μm and the beam length W is 200 μm, θ is about 20 degrees. However, when the thickness d is about 700 μm and the beam length W is 1000 μm, θ is about 60 degrees, which is not appropriate.

  As described above, by making the length of the slit opening 110 variable, the size of the linear, elliptical, or rectangular beam can be adjusted to a desired size. The beam can be shaped in accordance with the laser beam, or laser annealing can be performed on the region to be used.

  The present invention is not limited to the configuration of the above-described embodiment, and can be appropriately changed in design without departing from the gist of the invention.

  In this embodiment, a process of forming a thin film transistor (TFT) using a laser annealing apparatus according to the present invention is shown.

  As shown in FIG. 8A, a base film 801 is formed over a substrate 800 having an insulating surface. In this embodiment, a glass substrate is used as the substrate 800. Note that as the substrate 800 used here, a glass substrate such as barium borosilicate glass or alumino borosilicate glass, a quartz substrate, a ceramic substrate, a stainless steel substrate, or the like can be used. In addition, a substrate made of a flexible material typified by plastic or acrylic generally tends to have a lower heat-resistant temperature than other substrates, but if it can withstand the process of this step, Can be used.

  The base film 801 is provided to prevent alkali metal such as sodium or alkaline earth metal contained in the substrate 800 from diffusing into the semiconductor and adversely affecting the characteristics of the semiconductor element. Therefore, an insulating film such as silicon oxide, silicon nitride, or silicon nitride oxide that can suppress diffusion of alkali metal or alkaline earth metal into the semiconductor is used. Further, the base film 801 may have either a single layer or a stacked structure. In this embodiment, a silicon nitride oxide film is formed to a thickness of 10 to 400 nm by a plasma CVD method (Chemical Vapor Deposition).

  Note that in the case where a substrate containing an alkali metal or an alkaline earth metal, such as a glass substrate or a plastic substrate, is used as the substrate 800, a base film 801 is provided to prevent diffusion of impurities. Is effective, but it is not always necessary to provide the base film 801 when using a substrate such as a quartz substrate that does not cause significant diffusion of impurities.

  Next, an amorphous semiconductor film 802 is formed over the base film 801. The amorphous semiconductor layer 802 is formed with a thickness of 25 to 100 nm (preferably 30 to 60 nm) by a known method (a sputtering method, an LPCVD method, a plasma CVD method, or the like). As the amorphous semiconductor film 802 used here, silicon, silicon germanium, or the like can be used; here, silicon is used. When silicon germanium is used, the concentration of germanium is preferably about 0.01 to 4.5 atomic%.

Subsequently, as shown in FIG. 8B, crystallization is performed by irradiating the amorphous semiconductor film 802 with a laser beam 803 using the laser annealing apparatus of the present invention. In this embodiment, a 10 W, second harmonic, TEM ₀₀ mode (single transverse mode) Nd: YVO ₄ laser is used as the laser beam. By this laser beam irradiation, crystal grains continuously grown in the scanning direction are formed. Note that the laser is not limited to the laser described here, and a continuous wave laser or a pulsed laser having a frequency of 10 MHz or more may be used. As a continuous wave laser, single crystal YAG, YVO ₄ , YLF, YAlO ₃ , GdVO ₄ , alexandrite, Ti: sapphire, or polycrystalline YAG, Y ₂ O ₃ , YVO ₄ , YAlO ₃ , GdVO ₄ , As a dopant, a laser, an Ar laser, a Kr laser, a CO ₂ laser, or the like using one or more of Nd, Yb, Cr, Ti, Ho, Er, Tm, and Ta as a medium can be used. . As a pulse laser having a frequency of 10 MHz or more, single crystal YAG, YVO ₄ , GdVO ₄ , or polycrystalline YAG, Y ₂ O ₃ , YVO ₄ , YAlO ₃ , GdVO ₄ may be doped with Nd, Yb, Cr, Ti, You may use the laser etc. which use what added 1 type or multiple types among Ho, Er, Tm, and Ta as a medium.

  In order to reduce the size and improve the performance of electronic devices, it is necessary to arrange TFTs in a limited area as efficiently as possible and shorten the wiring. For this reason, the layout may not actually take advantage of the beam width. In other words, in an actual layout, when annealing is performed with a single laser width, the end of the beam often overlaps the portion where TFT formation is planned. If the TFTs are formed according to the layout as they are, the crystallization state of the semiconductor film included in the TFTs varies, which greatly affects the performance of the electronic device. For example, in the case of a layout (FIG. 9B) showing a wiring diagram of a light emitting element as shown in FIG. 9A, a transistor and a capacitor portion need to be a semiconductor film having good crystallinity. Even in such a case, laser irradiation may be performed while adjusting the beam width in two steps as shown in FIGS. 9C and 9D. In FIG. 9, 900 is a semiconductor film, 901 is a source signal line, 902 is a gate signal line, 903 is a current supply line, 904 is a switching TFT, 905 is a driving TFT, 906 is a capacitor, and 907 is a light emitting element. is there.

  In this embodiment, the beam width can be freely adjusted by moving the shielding plates 113a and 113b in the slit 103 shown in FIG. 1 so as to correspond to the layout. A layout is input in advance to a control device such as a computer that controls a motor that moves the shielding plates 113a and 113b. The control device sends a signal for controlling the motor according to the input layout, and the motor that has received this signal receives the shielding plate. A mechanism for adjusting the beam width by opening and closing 113a and 113b may be used.

  Further, when the slit 103 is used, a portion where the energy intensity of the laser beam is weak can be cut off. Therefore, by performing annealing using this beam, a linear, elliptical, or rectangular shape having a certain intensity or more is obtained. The laser beam can be irradiated to the amorphous semiconductor film on the substrate to perform uniform annealing.

  After that, the crystalline semiconductor film 804 formed by laser beam irradiation is patterned to form an island-shaped semiconductor film 805. Further, a gate insulating film 806 is formed so as to cover the island-shaped semiconductor film. For the gate insulating film 806, silicon oxide, silicon nitride, silicon nitride oxide, or the like can be used. In this case, a plasma CVD method or a sputtering method can be used as a film forming method. Here, a silicon nitride oxide film was formed to a thickness of 115 nm by a plasma CVD method.

  Next, a conductive film is formed over the gate insulating film 806 and patterned to form the gate electrode 807. After that, an impurity imparting n-type or p-type conductivity is selectively added to the island-shaped semiconductor film using a gate electrode or a resist pattern formed and patterned as a mask, and the source region 808 and the drain region 809, an LDD region 810, and the like are formed. Through the above steps, the N-channel TFTs 811 and 813 and the P-channel TFT 812 can be formed over the same substrate.

  Subsequently, an insulating film 814 is formed as a protective film thereof. The insulating film 814 is formed using a plasma CVD method or a sputtering method to form a silicon nitride film or a silicon nitride oxide film with a thickness of 100 to 200 nm with a single layer or a stacked structure. In this embodiment, a silicon oxynitride film having a thickness of 100 nm is formed by plasma CVD. By providing the insulating film 814, it is possible to obtain a blocking action that prevents intrusion of impurities such as oxygen and moisture in the air.

  Next, an insulating film 815 is further formed. Here, polyimide, polyamide, BCB (benzocyclobutene), acrylic, siloxane (siloxane is a skeleton formed by a bond of silicon (Si) and oxygen (O) applied by SOG (Spin On Glass) method or spin coating method. An organic group containing at least hydrogen (for example, an alkyl group or an aromatic hydrocarbon) is used as a substituent, a fluoro group may be used as the substituent, or An organic resin film containing at least hydrogen and a fluoro group may be used), a TOF film, an inorganic interlayer insulating film (insulating film containing silicon such as silicon nitride or silicon oxide), low-k ( Low dielectric constant) materials can be used. The insulating film 815 is preferably a film having excellent flatness because it has a strong meaning of relaxing and flattening unevenness caused by TFTs formed over a glass substrate.

  Further, the insulating film 814 and the insulating film 815 are patterned using a photolithography method to form a contact hole reaching the impurity region.

  Next, a conductive film is formed using a conductive material, and the wiring 816 is formed by patterning the conductive film. After that, when an insulating film 817 is formed as a protective film, a semiconductor device as shown in FIG. 8D is completed. Note that a method for manufacturing a semiconductor device using the laser annealing method of the present invention is not limited to the above-described TFT manufacturing process.

  Further, a crystallization step using a catalytic element may be provided before crystallization by laser beam irradiation. Nickel (Ni) is used as the catalyst element, but germanium (Ge), iron (Fe), palladium (Pd), tin (Sn), lead (Pb), cobalt (Co), platinum ( Elements such as Pt), copper (Cu), and gold (Au) can be used. When the crystallization process by laser beam irradiation is performed after the crystallization process using the catalytic element, the crystals formed during the crystallization by the catalytic element remain without being melted by the laser beam irradiation. Crystallization proceeds as a crystal nucleus.

  For this reason, the crystallinity of the semiconductor film can be further improved as compared with only the crystallization process by laser beam irradiation, and the surface roughness of the semiconductor film after crystallization by laser beam irradiation can be suppressed. Accordingly, variation in characteristics of semiconductor elements formed later, typically TFTs, can be further suppressed, and off-current can be suppressed.

  Note that after adding a catalytic element and performing heat treatment to promote crystallization, laser beam irradiation may be performed, or the heat treatment step may be omitted. Further, a heat treatment for crystallization may be performed, and laser treatment may be performed while maintaining the temperature.

  In this embodiment, an example in which the laser irradiation method of the present invention is used for crystallization of a semiconductor film is shown, but the semiconductor film may be used to activate an impurity element doped. The method for manufacturing a semiconductor device using the present invention can also be used for a method for manufacturing an integrated circuit or a semiconductor display device.

  Transistors for circuits such as drivers and CPUs (Central Processing Units) are preferably LDD structures or LDD structures that overlap with gate electrodes, and miniaturization of transistors is required for higher speed. desirable. Since the transistor completed in this embodiment has an LDD structure, it is preferably used for a circuit that requires high-speed operation.

  By using the present invention, various electronic devices can be completed using thin film transistors. A specific example will be described with reference to FIG.

  FIG. 10A illustrates a display device, which includes a housing 1001, a support base 1002, a display portion 1003, a speaker portion 1004, a video input terminal 1005, and the like. This display device is manufactured by using a thin film transistor formed by a manufacturing method shown in another embodiment for the display portion 1003. The display device includes a liquid crystal display device, a light emitting device, and the like, and specifically includes all information display devices such as a computer, a television receiver, and an advertisement display.

FIG. 10B illustrates a computer, which includes a housing 1011, a display portion 1012, a keyboard 1013, an external connection port 1014, a pointing mouse 1015, and the like. By using the manufacturing method described in another embodiment, application to the display portion 1012 and other circuits is possible. Furthermore, the present invention can also be applied to semiconductor devices such as a CPU and a memory inside the main body.
FIG. 10C illustrates a mobile phone, which is a typical example of a mobile terminal. This mobile phone includes a housing 1021, a display portion 1022, operation keys 1023, and the like. Since electronic devices such as PDAs (Personal Digital Assistants, information portable terminals), digital cameras, and small game machines are portable terminals, the display screen is small. Therefore, by forming a functional circuit such as a CPU or a memory using the fine transistor shown in another embodiment of the present invention, the size and weight can be reduced.

  Further, the transistor created in this embodiment can be used as an ID chip. For example, by using the manufacturing method shown in another embodiment, it can be used as an integrated circuit or memory in an ID chip, or as an ID tag. When used as a memory, it is possible to record production stage processes such as production location, producer, date of manufacture, processing method, etc., and merchandise distribution processes. It becomes easy for wholesalers, retailers, and consumers to grasp this information.

  Furthermore, when it is used as an ID tag equipped with a wireless function, it can be used in place of a conventional bar code to simplify product accounting and inventory work.

  As described above, the applicable range of the semiconductor device manufactured according to the present invention is so wide that the semiconductor device manufactured according to the present invention can be used for electronic devices in various fields.

The figure which shows the outline | summary of the laser irradiation apparatus of this invention The figure which shows the outline | summary of the slit of this invention The figure which shows the scanning state of the beam on the substrate The figure which shows the other scanning state of the beam on a board | substrate Diagram showing the reflection state of the beam on the substrate The figure which shows the outline of the conventional laser irradiation device The figure which shows the outline | summary of the other conventional laser irradiation apparatus. The figure which shows the outline of creation of TFT using invention of this application Diagram showing the outline of laser irradiation using the invention of the present application The figure which shows the example of the electronic device using invention of this application

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Laser oscillator 102 ... Diffractive optical element 103 ... Slit 104 ... Mirror 105 ... Condensing lens 106 ... Non-single crystal semiconductor film 107 ... Substrate 108 ... X-axis stage 109 ... Y-axis stage 110 ... Slit opening 111 ... Motor 112 ... Screw shaft 113 ... Shielding plate 114 ... Supporting piece 120 ... Beam light 130 ... TFT
140: Incident light 141: Upper surface reflected light 142: Lower surface reflected light

Claims (10)

  A laser irradiation apparatus having a laser oscillator, a diffractive optical element, a slit, and a condenser lens, wherein the slit is capable of changing a length of a slit opening.   In a laser irradiation apparatus having a laser oscillator, a diffractive optical element, a slit, and a condenser lens, the slit can change the length of the slit opening, and the laser beam has a different length with respect to the irradiation surface The laser irradiation apparatus characterized by being able to irradiate.   In a laser irradiation apparatus having a laser oscillator, a diffractive optical element, a slit, and a condenser lens, the slit can change the length of the slit opening, and the laser beam has a different length with respect to the irradiation surface Can be irradiated obliquely. A laser irradiation apparatus characterized by that.   4. The laser irradiation apparatus according to claim 1, wherein the length of the slit opening in the longitudinal direction is variable. 5. In any one of Claims 1 thru | or 4,
The laser irradiation apparatus, wherein the slit is located between the diffractive optical element and the condenser lens and is located on an optical path of a laser beam emitted from the laser oscillator.   6. The laser irradiation apparatus according to claim 1, wherein the laser from the laser oscillator is a continuous wave solid laser, a gas laser, or a metal laser. In the claims 1 to any one of claims 6, laser from the laser oscillator, _YAG single _{crystal, YVO 4, YLF, YAlO 3} , GdVO 4, Alexandrite, Ti: sapphire or polycrystalline YAG,, Continuous oscillation using Y ₂ O ₃ , YVO ₄ , YAlO ₃ , GdVO ₄ as a medium with one or more of Nd, Yb, Cr, Ti, Ho, Er, Tm, and Ta added as dopants A laser irradiation apparatus characterized in that it is a kind selected from the above lasers. In the claims 1 to any one of claims 6, laser from the laser oscillator, the laser irradiation apparatus, characterized in that the one selected from Ar laser of a continuous oscillation, Kr laser, CO ₂ laser.   6. The laser irradiation apparatus according to claim 1, wherein the laser from the laser oscillator is a pulse oscillation laser having a frequency of 10 MHz or more. 10. The laser from the laser oscillator according to claim 9, wherein single crystal GdVO ₄ , YVO ₄ , YAG, or polycrystalline YAG, Y ₂ O ₃ , YVO ₄ , YAlO ₃ , GdVO ₄ are doped with Nd, Yb as dopants. , Cr, Ti, Ho, Er, Tm, Ta A laser irradiation apparatus characterized by being a laser having a medium added with one or more of them.

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